Metabolic Aspects of PCOS: Treatment With Insulin Sensitizers 2015 Ed.

3. Clinical Features

Mariagrazia Stracquadanio¹ and Lilliana Ciotta¹

(1)

Obstetrics and Gynecological Pathology, P.O. “S. Bambino”, University of Catania, Catania, Italy

Keywords

Menstrual disordersAnovulationInfertilityHirsutismAcneAndrogenic alopeciaHypertensionDiabetesDyslipidemiaObesityNAFLDGestational diabetesPregnancy-induced hypertensionOocyte qualityRecurrent pregnancy loss

3.1 Endocrine Aspects of PCOS

Polycystic ovary syndrome (PCOS) is a chronic and self-perpetuating endocrine disorder, whose clinical, endocrine, and metabolic manifestations affect the whole life course of a patient. In PCOS, in fact, we can distinguish two sides of the same coin: endocrine and metabolic aspects.

A polycystic ovary appears enlarged with a thickened albuginea that has a porcelain appearance. In the subcapsular layer, there are many follicles measuring 2–10 mm in diameter, reduced number of granulosa cells, and a characteristic theca cell hyperplasia.

Thus, the fundamental abnormality is the presence of a raised number of follicles recruited with primary maturation block and increased atretic follicles.

3.1.1 Endocrine Pattern

3.1.1.1 Gonadotropins

PCOS is considered a normo-gonadotropic normo-estrogenic anovulatory disorder, but it is characterized by elevated LH serum concentrations with an inverted FSH/LH ratio [1].

PCOS follicles are present in large numbers, but they are arrested at an early to mid-developmental state and fail to mature even when they are exposed to normal FSH levels [2–4]. On the other hand, FSH levels do not increase during the early follicular phase to stimulate follicular maturation [5].

The resulting low estrogen and progesterone levels do not produce a negative feedback on LH secretion, and this is the major cause for the high serum LH concentrations in women with PCOS [6].

Despite these findings, gonadotropin levels have never been included in any of the diagnostic criteria for PCOS, especially because of the pulsatile nature of LH release [7–9].

3.1.1.2 Sex Hormones

Hyperandrogenemia is the biochemical feature of PCOS. Elevated circulating androgen levels are observed in 80–90 % of women with oligomenorrhea [10].

In particular, a decreased SHBG (sex hormone-binding globulin) production with a consequent increase in free testosterone levels is reported. Furthermore, some authors suggest that, vice versa, SHBG levels are decreased in PCOS due to the effects of testosterone and insulin of decreasing hepatic production of SHBG [11, 12].

Ovaries are the main sources of increased androgens in PCOS, but even adrenal androgen excess is a common feature of the syndrome (approximately 20 % of PCOS women): an increased secretion of adrenocortical precursor steroids basally and in response to ACTH, such as pregnenolone, 17-hydroxyprogesterone (17-OHP), dehydroepiandrosterone (DHEA), and androstenedione (A), was demonstrated [13, 14].

It has been suggested that androgens enhance apoptosis in the granulosa cells of preantral and early antral follicles [15]. Moreover, a study found that the exposure to excessive androstenedione stimulates a premature luteinization of granulosa cells, most likely due to the loss of communication between the oocyte and the granulosa cell [16].

Due to the pulsatility of LH, only one blood parameter is not enough for the PCOS diagnosis, and there is no unanimous consensus on which androgen blood levels should be considered for a precise diagnosis (total or free testosterone, testosterone/SHBG ratio, or androstenedione). Usually, elevated levels of only DHEA or 17-OHP may exclude the diagnosis of PCOS [17].

3.1.1.3 Estrogens and Progesterone

Estradiol levels are constant, without the normal mid-cycle increase, while the levels of estrone are increased because of extraglandular aromatization of increased circulating androstenedione levels [18–20].

As a consequent of anovulation, progesterone levels are low in PCOS women; moreover, some authors reported that endometrial responsiveness to progesterone is reduced in PCOS women [21, 22] and that total endometrium PR (progesterone receptor) expression is higher in women with PCOS who have anovulation compared to women with PCOS who still ovulate [23].

Furthermore, the increased PR expression in epithelial cells is greater than that instromal cells in women with PCOS, suggesting that lower binding of progesterone in stromal cells could lead to the promotion of estradiol-induced epithelial cell proliferation in PCOS women.

It has been hypothesized that lack of progesterone-induced and PR-mediated stromal cell proliferation could be a cause of progesterone resistance in PCOS patients [24].

3.1.1.4 AMH

Anti-Mullerian hormone (AMH) belongs to the transforming growth factor-β (TGF-β) superfamily. In women, AMH is produced by the granulosa cells of follicles from the stage of the primary follicle to the initial formation of the antrum. In female newborn, AMH is undetectable, but it increases gradually until puberty, remaining stable in the reproductive period [25].

Reduction of AMH levels in serum is the first indication of a decline in the follicular reserve of the ovaries. Moreover, AMH concentration remains stable during the cycle [26].

Since AMH level reflect the number of developing follicles, its measurement may be used as a marker of ovarian follicle damage in PCOS.

AMH levels are also probably related to the follicular arrest, during the selection process of the dominant follicle: AMH inhibits the recruitment of primordial follicles into the pool of growing follicles and decreases their receptiveness to FSH [27–29].

The first studies regarding AMH levels in PCOS women showed that AMH levels are higher than in healthy controls [30, 31]. Subsequent data indicated that these levels are related to increased number of small antral follicles of 2–5 mm diameter [32]: this correlation was found to be the strongest one [33].

The cause of the increased AMH production in PCOS is unknown: it is mainly ascribed to the increased production of AMH by each follicle, and it is not just a consequence of an increased follicle number, suggesting intrinsic granulosa cell dysregulation in PCOS [34, 35].

AMH levels are increased in proportion to PCOS clinical severity, as reflected by the antral follicle count [36, 37].

Furthermore, blood AMH appears to be associated with androgen levels, and so it has been proposed as a diagnostic marker for ovarian hyperandrogenism [38].

Some studies demonstrated, in fact, that AMH is positively correlated with total testosterone levels in normal-weight PCOS women [39].

AMH levels, as written before, decrease with age in women with normal ovulatory cycles; in PCOS women, this decline has a slower reduction rate, and it could be because of a decelerated ovarian aging, probably due to the negative effect of AMH on the recruitment of primordial follicles.

3.1.2 Clinical Endocrine Features

The clinical scenario of PCOS is very heterogeneous, and the symptoms are related to the ovarian dysfunction and hyperandrogenism.

This section describes the clinical characteristics of a PCOS woman, while the diagnostic pathway can be found in Chap. 6.

3.1.2.1 Menstrual Disorder

Since menarche, or after a short period, menstrual cycles show an irregular rhythm. In many cases they gradually distance themselves from each other, up to result in oligomenorrhea or in permanent amenorrhea. Menstrual dysfunction in women affected by PCOS may manifest in different ways, but the most common way is anovulation with erratic bleedings.

Although the presence of oligomenorrhea indicates ovulatory dysfunction, apparent eumenorrhea does not completely rule out anovulation [40].

Therefore, ovarian dysfunction usually manifests as oligomenorrhea/amenorrhea resulting from chronic oligo-ovulation/anovulation. The majority of women complaining oligomenorrhea (up to 80–90 %) are affected by PCOS [41].

A significant relationship between the degree of menstrual dysfunction and the degree of insulin resistance present was observed. After adjusting for BMI, age, and race, all PCOS subjects with menstrual cycles longer than 35 days had significantly higher mean HOMA-IR levels than controls, with those with cycle length longer than 3 months having the highest one [42]. Confirming these findings, it was reported also that among PCOS women insulin resistance was significantly worse in amenorrheic patients [43].

As consequent, prolonged anovulation can be the cause of dysfunctional uterine bleeding, which may mimic regular menstrual cycles.

In addition, the chronic anovulation implies prolonged estrogen excess (particularly in obese phenotype women) and lack of progesterone, resulting in atypical endometrial hyperplasia, which is the precursor of endometrial carcinoma [44, 45].

It is generally recommended that greater than four cycles per year may protect the endometrium [46].

3.1.2.2 Infertility

PCOS is the most common cause of anovulatory infertility: 90 % of women attending infertility clinic for anovulation disorder are affected by PCOS.

Despite these data, 60 % of women with PCOS are fertile, while time to conceive is often increased [41].

Moreover, infertile PCOS women are overweight in 90 % of cases.

Fifty percent of PCOS women experience recurrent pregnancy loss [47]: it is not clear whether these defects are caused by uterine dysfunction itself, by possible interrupted interaction between uterine cells and the developing embryo, or by insulin-related disorder.

The new guidelines suggest that PCOS is a risk factor for infertility only in the presence of oligo-ovulation or anovulation. However, there are no clear data about the fertility of PCOS patients who have normal ovulatory function [48].

3.1.2.3 Hirsutism

Hirsutism is defined as the presence of excessive terminal hairs in areas of the body that are androgen dependent and usually hairless or with limited hair growth, such as the face, chest, areolas, and abdomen [49].

Terminal hair is different from “vellus” hair, because the latter is the prolonged version of “lanugo” (the hair that covers fetuses and is shed gradually after birth) which covers all body surface except lips, palms, and soles; specifically, terminal hair is the pigmented, longer, coarser hair that covers the pubic and axillary areas, scalp, eyelashes, eyebrows, male body, and facial hair [50].

Hirsutism should be differentiated from hypertrichosis, which is the overgrowth of vellus in a nonsexual pattern distribution, usually related to persistence of the highly mitotic anagen phase of the hair cycle [51, 52].

Terminal hair growth requires androgen stimulation, specially testosterone and dihydrotestosterone (DHT) that can bind to the androgen receptor and promote hair follicle changes [50, 53].

Androgens, in fact, are the most significant hormones associated with hair growth modulation. They are necessary for terminal hair and sebaceous gland development and cause differentiation of pilosebaceous units into either a terminal hair follicle or a sebaceous gland. They are involved in keratinization, increased hair follicle size, hair fiber diameter, and the proportion of time that terminal hair spends in the anagen phase [54].

Thus, hyperandrogenemia is the cause of hirsutism, but the percentage of hair growth is not proportional to the degree of hyperandrogenism, supporting the important role for androgen receptor localization (keratinocytes, sebaceous glands, hair dermal papilla cells) and sensitivity in the development of hair patterns [55].

3.1.2.4 Acne and Seborrhea

Sebaceous glands are also androgen-dependent structures: sebocytes are highly sensitive to androgen signaling, which is worsened in PCOS, leading to the development of acne and seborrhea [56].

Androgens stimulate sebocyte proliferation (particularly in the mid-back, chin, and forehead) and secretion of sebum, which is a mixture of lipids including glycerides, squalene, free fatty acids (FFA), and cholesterol [57].

Local bacteria complicate the process by secreting lipolytic enzymes: they break down those triglycerides produced in the sebocyte; these FFAs are released into sebaceous ducts by apocrine glands, and they are responsible for the typical unpleasant odor [58].

3.1.2.5 Androgenic Alopecia

An opposite clinical feature is androgenic alopecia, which is a disorder characterized by miniaturized hair, due to an increased telogen/anagen ratio, and associated to genetic susceptibility related to increased 5α-reductase activity in the hair follicle. This increased enzymatic activity promotes the local conversion of testosterone into DHT, which has an increased androgen action.

Seventy percent of women with alopecia areata have PCOS with elevated levels of androstenedione and testosterone [59]. The balding pattern is mainly in the frontal and parietal scalp zones, while the occipital area has a great hair density [60].

3.1.2.6 Other Clinical Features

In rare cases, virilization patterns can be observed: they include increased size of clitoris, muscle mass hypertrophy, deep voice, temporal balding, and masculine aspect. In these cases, however, a lower ovarian or adrenal androgen-secreting neoplasm must be excluded.

Moreover, in PCOS women, nails could be affected by alterations, in the form of onycholysis [61] (separation of the nail plate from the nail bed caused by disruption of the onychocorneal band) and onychorrhexis [62] (splitting of nails in lengthway bridges). Nowadays the association of these nail diseases with hyperandrogenemia is not completely understood.

In literature, an unusual case of atypical oral hirsutism secondary to PCOS was described: a 19-year-old girl complained of the appearance of hairs on the sulcular epithelium of the retroincisor palatal papilla, relapsing after surgical excision. PCOS diagnosis was confirmed by clinical data (oligomenorrhea, face hirsutism, and acne), by serum studies, and by the symptom improvement after combined hormonal therapy [63].

3.1.2.7 PCOS and Thyroid Dysfunction

The most prevalent autoimmune disease in women is autoimmune thyroiditis (AIT), with a prevalence ranging from 4 to 21 %: it depends on age [64], diagnostic criteria, genetic differences, geographical origin, and iodine intake [65, 66]. In the past, a German study underlined the association between PCOS and AIT, but the pathogenesis of this relationship is not clear.

Few explanations were suggested, but none of these appears to be conclusive:

· Probable common genetic predisposition

· Imbalance between estrogens and progesterone, and the consequences of the stimulatory effect of estrogens on the immune system [67]

· Low-grade inflammatory state characteristic of PCOS

Recently, it has been shown that there is a higher prevalence of subclinical hypothyroidism in young women with PCOS compared with that reported for the general young women population [68].

Moreover, Mueller et al. [69] observed that PCOS patients with subclinical hypothyroidism had a higher prevalence of IR and a higher BMI.

3.2 Metabolic Aspects of PCOS

“Metabolic flexibility” is the capacity of the body to rapidly switch from predominant lipid oxidation (with high rates of fatty acid uptake in low-insulin conditions) to predominant glucose oxidation and storage with suppression of lipid oxidation in high-insulin conditions [70].

Few studies showed that obese and/or diabetic and/or insulin-resistant individuals, as compared with healthy lean individuals, have an impaired metabolic flexibility [71, 72].

Insulin resistance and the associated metabolic abnormalities are frequent findings in women with polycystic ovary syndrome [73].

Many women with PCOS meet the criteria for the metabolic syndrome (MS), as they report a higher incidence of hypertension, dyslipidemia, and visceral obesity [74].

Up to 43 % of nondiabetic PCOS women meet MS criteria before the end of their fourth decade, and most of them before the end of their third decade of life [75, 76].

This prevalence is four times higher than that observed in women aged 20–30 years and twice that of women between the ages of 30 and 40 years [77].

The prevalence of metabolic syndrome is similar across racial backgrounds [78].

Moreover, it was found that the prevalence of metabolic syndrome is higher in adolescent girls with PCOS: 37 % against 5 % of control non-PCOS girls [79].

The most common phenotypes in parents of adolescents with PCOS were found to be excessive weight and metabolic syndrome, particularly in fathers in whom the prevalence of MS and central obesity was 1.5–2-fold greater than expected in the general population [80].

The essential components of MS include insulin resistance or central obesity with at least two of hypertension, elevated triglycerides, decreased HDL-C levels, or elevated fasting glucose [81].

Insulin resistance, and consequent compensatory hyperinsulinemia, appears to be the central pathophysiologic mechanism that links PCOS to its metabolic disorders; in fact, few studies reported that PCOS women are more insulin resistant than controls who are matched for age and BMI [78].

Disturbance in the insulin’s ability to bind to its receptor or in the transport mechanism across the cell membrane may lead to a state of a reduced sensitivity to insulin, or insulin resistance. Furthermore, pancreatic β-cell secretory dysfunction has also been reported [82, 83], and a reduction in hepatic insulin extraction contributes to the high insulin levels as well [84, 85].

Compensatory hyperinsulinemia is important in the development of metabolic abnormalities and also contributes to the high androgen levels, peculiar of PCOS women. As largely described in Chap. 2, it is important to remember that insulin binds to its receptor on the ovarian theca cell and it acts enhancing LH-stimulated androgen production [86]. Moreover, insulin can also act indirectly to raise free testosterone serum concentration by inhibiting the hepatic production of SHBG [12].

Although obesity is a major factor for the development of insulin resistance in PCOS, it is now well known that a component of insulin resistance is independent of body weight [87].

To underline the link between PCOS and metabolic syndrome, it is important to report that coronary heart disease, as well as cerebrovascular disease, is more common in postmenopausal PCOS patients. Persisting high androgen levels through the menopause, obesity, and maturity-onset diabetes mellitus are proposed as the main mechanisms accounting for the increased risk [88].

3.2.1 The Role of the Adipocyte in Linking PCOS to Metabolic Syndrome

Adipose tissue is nowadays considered not only a storage tissue but also a proper endocrine organ, metabolically active [89–92].

Adipose tissue responds to chronic changes in energy balance and nutrient content by altering the proliferation of pre-adipocytes, their differentiation into mature adipocytes, the growth and hypertrophy of adipocytes, and, finally, their apoptosis and necrosis [93]. In addition, rates of angiogenesis, extracellular matrix remodeling, and the relative distribution of the resident immune cell population in adipose tissue are modified in response to changes in nutritional status [94]. Thus, it is evident that adipose tissue acts as an enormous endocrine organ, secreting a variety of signaling molecules that regulate feeding behavior, energy spending, metabolism, reproduction, and endocrine and immune function [95].

Adipocytes secrete adiponectin, leptin, visfatin, tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), plasminogen activator inhibitor-1 (PAI-1), resistin, and angiotensinogen: thus, adipose tissue results to be metabolically active [96, 97].

Adiponectin is a 244-amino acid protein that is expressed in white adipose tissue [98].

This adipokine expression within adipocytes is downregulated in obesity [99], and the result is that serum levels of adiponectin are inversely correlated with body weight [100].

Adiponectin has insulin-sensitizing, anti-atherogenic, and anti-inflammatory properties [101, 102]. It is well known that adiponectin has an important role in mediating the effects of increased fat mass on insulin sensitivity [103]: in fact, its low serum levels seem to be involved in conditions associated with insulin resistance, such as type II diabetes and obesity [104–106]; moreover, lower levels of serum adiponectin are present in PCOS women [107].

It also has been reported that adiponectin inhibits theca cell androgen production: suppressed levels of adiponectin may allow enhanced ovarian androgen production in PCOS women [108].

Leptin controls the fat disposition modulating its accumulation in the heart, liver, and kidneys; besides, it is involved in the control of vascular tone by producing a pressure action and opposing the NO-mediated relaxing function [109]: this could be associated with cardio-metabolic syndrome.

In humans, there is a strong association between the percentage of body fat and serum leptin levels [110]; some authors found that hyper-leptinemia has a positive relationship with insulin-resistant PCOS women [111], even if more studies are needed to confirm it.

Hyper-leptinemia seems to lower the sensitivity of dominant ovarian follicles to insulin-like growth factor 1 (IGF-1), which is implicated in the mechanism of anovulation [112].

Visfatin is a multifunctional protein that plays a number of roles including the regulation of metabolism and inflammation, and it is also involved in the insulin resistance mechanism [113, 114].

Few recent studies have demonstrated that visfatin levels are significantly higher in PCOS women comparing to the healthy controls [115], even when considering only the overweight and obese subgroups [116].

It has been demonstrated that in women with PCOS, adipocyte diameter is 25 % greater than the diameter of adipocytes taken from obese control women with comparable BMI: adipocyte seems to be hypertrophic [117].

Adipocyte hypertrophy in PCOS may be a consequence of variations in storage and/or adipocyte lipolytic capacity. Thus, obesity in women with PCOS is mainly characterized by an increase in fat cell size (hypertrophic obesity) rather than an increase in fat cell number (hyperplastic obesity) [118].

In PCOS subcutaneous adipocytes, there is a reduced catecholamine-mediated lipolysis [119], and maybe there is an implication of testosterone as a possible contributory factor in this process [120]. Greater lipolysis within visceral adipocytes results in hepatic insulin resistance through increased hepatic influx of portal free fatty acids; reduced lipolysis within subcutaneous adipocytes is likely to be one explanation for adipocyte hypertrophy and consequent insulin resistance [108].

Studies on the molecular insulin signaling pathways within PCOS adipocytes have demonstrated that the number of insulin receptors and the affinity of these receptors for insulin are normal [121–123]. Moreover, there are evidences that, in PCOS adipocytes, basal auto-phosphorylation of the insulin receptor β-subunit is normal, but insulin-dependent auto-phosphorylation is significantly reduced [123].

The existing literature suggests a large number of possible defective post-insulin receptor molecular mechanisms that may explain adipocyte’s insulin resistance in PCOS, although the actual mechanism involved and the determinants of adipocyte size in PCOS are not fully understood [108].

In the past, Danforth hypothesized that the inability to differentiate sufficient new subcutaneous adipocytes in response to chronic excessive energy intake may explain the metabolic dysfunction observed in some obese women: thus, a deficiency in either the proliferation or differentiation capacity of adipocytes leads to the redistribution of fat from subcutaneous to visceral depots and also to other tissues such as the liver and skeletal muscle, where the ectopic fat causes insulin resistance [124].

Furthermore, steroidogenic activity within the adipocyte plays a crucial role in the development of PCOS, particularly the hyperandrogenemia associated with PCOS: this could be the link between obesity and hyperandrogenemic features [108].

Although the predominant source of raised androgens in PCOS women is ovarian, adrenal androgen secretion is also important [125]; moreover, peripheral conversion of androstenedione and DHEAS accounts for up to 50 % of circulating testosterone in PCOS women, and the major peripheral site is the adipose tissue [126].

The 5α-reductase enzyme is present in the adipocyte cell and it converts testosterone into the more potent 5α-dihydrotestosterone (DHT), and it is also involved in the catabolism of cortisol [125].

It is supposed that PCOS women have enhanced peripheral 5α-reductase activity compared with age and BMI-matched control women [127–130]. This causes an increased production of DHT, increased catabolism of cortisol, and consequent reduced feedback of cortisol on the pituitary corticotroph cells [125].

Furthermore, increasing adipose tissue mass is directly associated with increasing levels of angiotensin II from the increased secretion of angiotensinogen by adipose tissue; this increase could contribute to hypertension and worsen insulin resistance [131].

On the other hand, few molecules secreted by adipocytes are involved in macrophage function, including monocyte chemoattractant protein-1 (MCP-1), macrophage migration inhibitory factor, and macrophage inflammatory protein (MIP)-1α which are upregulated in obesity [132]. Adipose tissue resident macrophages from obese women are activated and also express few proteins such as MIP-1α, MCP-1, and related inflammatory cytokines, which may play a role in the development of obesity-induced insulin resistance [118]. Most adipose tissue TNF-α, inducible nitric oxide synthase, and IL-6 seem to be expressed by adipose tissue macrophages, rather than adipocyte [94]. IL-6 inhibits lipoprotein lipase activity, stimulates aromatase activity, and increases the hepatic production of triglycerides [133]. IL-6 is stimulated by TNF-α: the latter stimulates C-reactive protein (CRP), which is highly associated with obesity, insulin resistance, and endothelial dysfunction; PCOS women seem to have higher levels of CRP [134, 135] and, specifically, of hs-CRP (high-sensitive CRP), which is the most specific marker [136].

Elevation of these inflammatory markers is in accord with the hypothesis that atheroma formation is primarily an inflammatory condition [137].

3.2.2 The Role of Vitamin D in the Development of Metabolic Syndrome in PCOS Women

Few evidences suggest that vitamin D deficiency could be a causal factor in the pathogenesis of metabolic syndrome in PCOS women [138].

It is well known that the vitamin D receptor gene regulates 3 % of the human genome, including genes essential for glucose and lipid metabolism and blood pressure regulation [139–141].

In fact, clinical studies had reported insulin resistance and obesity association with hypovitaminosis D [138, 142, 143].

The mechanism underlying the association between low vitamin D levels and insulin resistance is not completely assumed. The suggested hypotheses are the following:

· Vitamin D may have a positive effect on insulin action by stimulating the expression of insulin receptor and improving insulin receptiveness for glucose transport [140].

· Vitamin D regulates extracellular and intracellular calcium, which is important for insulin-mediated intracellular processes in insulin-responsive tissue (skeletal muscle and adipose tissue) [140].

· Vitamin D has a modulating effect on the immune system, so hypovitaminosis D might have a pro-inflammatory action, which is associated with insulin resistance [144, 145].

Moreover, it is not fully understood whether vitamin D insufficiency results from obesity and/or whether obesity is a consequence of hypovitaminosis D.

Despite there is not a clear consensus regarding its optimal value, a level of 30 ng/ml indicates a sufficient vitamin D status [139]; concentrations of 20–30 ng/ml are considered as vitamin D insufficiency, while a level less than 20 ng/ml represents a vitamin D deficiency [139].

In a recent study, 72.8 % of PCOS women showed values below the abovementioned normal cutoff; a significant association of hypovitaminosis with increased levels of both fasting and stimulated glucose and insulin, elevated HOMA-IR, and incidence of MS was demonstrated [146].

Furthermore, vitamin D levels were significantly lower in hirsute woman, as shown in previous study [138, 147]. For example, distress caused by the excessive hair might lead to hypovitaminosis D because of the decreased sun exposure of hirsute women.

Vitamin D receptor is present in keratinocytes of the outer root sheath as well as in cells of the bulge, indicating an important role of vitamin D in hair follicle cycling [144].

3.2.3 Metabolic Syndrome and Associated Disorders

3.2.3.1 Visceral Obesity

The prevalence of obesity in PCOS varies from approximately 10 % up to 50 % [148, 149].

A likely explanation for the mechanism underlying the development of obesity in women with PCOS is the combined effect of a genetic predisposition to obesity in the context of an “obesogenic” environment (poor diet and reduced exercise). The development of obesity in PCOS patients, in turn, amplifies and unmasks the biochemical and clinical abnormalities characteristic of this condition [125].

Obese PCOS women have lower levels of SHBG, DHEAS, DHEA, IGF-1, and HDL and higher LDL compared with the nonobese PCOS controls [150].

It is important to underline that all overweight/obese people are not insulin resistant, and those who are insulin resistant are not all obese.

Previous researches have studied the importance of fat distribution patterns as risk factor for cardiovascular and metabolic disease such as diabetes mellitus [151, 152].

In fact, gluteo-femoral obesity is less associated with insulin resistance than is central or android obesity [153].

The gynoid type of fat distribution, where fat accumulates around the hips, thighs, and buttocks, is developed during female puberty and is maintained during the fertile phase [152, 154].

Approximately 50–60 % of PCOS women are characterized by a so-called “android” distribution of body fat, whereby a disproportionate quantity of adipose tissue is distributed in the visceral depot [155, 156]: they have a higher trunk/peripheryfat ratio [157].

This upper body fat distribution has been explained mainly by androgen excess [158], and it is an independent factor of BMI [159]: the pathogenic mechanisms involved have not yet been defined.

In women affected by PCOS, android body fat distribution per se contributes to hyperandrogenemia, through its adverse effects on insulin sensitivity and consequent ovarian co-gonadotropic effects of hyperinsulinemia.

Hyperinsulinemia itself contributes to obesity by the anabolic effect on fat metabolism through the adipogenesis process: the result is an increased uptake of glucose into adipocytes, the production of triglycerides, and the inhibition of hormone-sensitive lipase [160].

Therefore, there is a vicious cycle in which android fat produces android fat and exacerbates the predisposition toward weight gain [125].

Visceral fat, or abdominal fat, is metabolically distinct from subcutaneous fat; it is resistant to the anti-lipolytic effects of insulin and releases excessive amounts of free fatty acids, which leads to IR in the liver and muscle. In response to it, in the liver, there is an increased gluconeogenesis, and in the muscle there is an inhibition of insulin-mediated glucose uptake [161–163].

Excess fat itself contributes to IR at the level of the adipocyte: when fat cells become too large, they are unable to store additional lipids, and then, fat is stored in the muscle, liver, and beta cells of the pancreas [164]. Visceral fat also produces excess of 11-beta-hydroxysteroid-dehydrogenase-1 [163], an enzyme that converts inactive cortisone to the biochemically active cortisol: the latter is able to promote central adiposity and IR [165].

3.2.3.2 Dyslipidemia

The probability of a metabolic disorder in families of PCOS patients is 2.7-fold higher compared with normal families, and the relative risk for developing dyslipidemia is 1.8 [166].

Dyslipidemia is reported in up to 70 % of patients who have PCOS, according to the National Cholesterol Education Program (NCEP) guidelines [167].

Dyslipidemia in PCOS women seems to be well understood, but which are the determinant factors of this pattern? Insulin, estrogens, and androgens are each well known to alter lipoprotein lipid metabolism [168]. All of them influence hepatic lipase activity, which is important in reductive metabolism of intermediate-density lipoproteins to small dense LDL particles; greater activity of this enzyme was found in PCOS women [169].

Insulin stimulates lipogenesis in arterial and adipose tissues via an increased production of acetyl CoA and the entry of glucose and triglycerides [170].

PCOS women have higher Apo-CIII levels compared to non-PCOS controls [171]: understanding its metabolism is helpful to deeply comprehend the pathophysiology of dyslipidemia in PCOS.

In states of IR, it has been shown an increased synthesis of ApoC-III [172]: in PCOS, with central obesity more free fatty acids flow into the portal vein and more glucose is available, causing altered apolipoprotein lipid metabolism. The ratio of ApoC-II/CII is increased and triglycerides carried in VLDL are broken into more atherogenic small LDL particles, which circulate and enter the arterial wall to initiate inflammation. With elevated triglycerides, VLDL lipolysis is slowed, causing greater residence time for ApoB, remnant particles, LD particles and small LDL-particles. ApoC-I, recently shown to be elevated in normal-weight PCOS women, blocks lipoprotein lipase, cholesterol ester transferase, lecithin cholesterol acyltransferase, VLDL receptors and LDL receptors in the liver. All of these events lead to more exposure of the blood vessel wall to entry of atherogenic particles with the potential for setting inflammation and atherogenesis. [168]

Moreover, insulin increases the levels of HMG-CoA reductase, the rate-limiting enzyme in the synthesis of cholesterol: this effect may contribute to the raised cholesterol level, which is also a feature of hyperinsulinemia [173].

Hyperandrogenism and lipid metabolism are closely related: in fact, it has been observed that testosterone has a deleterious effect on lipid profile [174, 175]. Testosterone has been involved in lowering HDL-C levels, an effect attributed to the upregulation of two genes implicated in the catabolism of HDL: scavenger receptor B1 (SR-B1) and hepatic lipase [176].

The most common lipid profile found in PCOS individuals is characterized by [176–182]:

· Increased levels of LDL cholesterol (especially raised amounts of types III and IV small LDL particles [176])

· Increased VLDL cholesterol

· Increased triglycerides

· Reduced levels of HDL cholesterol (particularly decreased HDL2, the most anti-atherogenic HDL subtype)

Particularly, a study has demonstrated that the incidence of high triglycerides increased progressively from the lean to the obese PCOS women, and the incidence of low HDL was three times higher in the overweight than in the lean PCOS subgroup [183].

HDL-C has several functions: inhibition of LDL-C oxidation, transport of cholesterol from peripheral cells to the liver, anti-apoptotic effects, and antithrombotic and antioxidant effects. For this reason, low HDL-C is considered an independent cardiovascular risk factor: thus, women with PCOS may have a higher cardiovascular risk than normal women at the same BMI level [184].

Furthermore, these lipid disorders are exacerbated among those women who develop glucose intolerance in association with PCOS; in fact, 88 % of women with PCOS and IGT or type II diabetes have an abnormal lipid profile, compared with 58 % of women with PCOS and normal glucose tolerance [177].

Even PCOS adolescents have less favorable blood lipid profiles, with higher LDL-C and lower levels of HDL-C, and they appear to be more insulin resistant than their peer control with higher fasting C peptide levels [185].

3.2.3.3 NAFLD (Nonalcoholic Fatty Liver Disease)

NAFLD represents a disease spectrum ranging from steatosis hepatitis (SH or NAFL) to nonalcoholic steato-hepatitis (NASH), characterized by hepatocyte injury, inflammation, and fibrosis, which can progress to cirrhosis in 25 % of cases, with its long-term complications, such as portal hypertension, liver failure, and hepatocellular carcinoma [186].

The hepatic steatosis is histopathologically characterized by the accumulation of triglycerides, both in the form of macro- and microvesicles, in more than 5 % of hepatocytes. These “fatty hepatocytes” are usually peri-venular located, and they are mainly present at the level of the “portal areas.” The pool of fatty acids available for the synthesis of triglycerides is related to the balance between their formation and utilization. The deposition of triglycerides into the hepatocytes depends on both of these reactions: thus, the development of a fatty liver is the consequence of a dysfunction in different metabolic pathways.

There are important relationships between peripheral insulin resistance and hepatic fat deposition. High intake of calories in sedentary individuals who are genetically susceptible induces a state of IR, which involves an increased lipolysis, as a result of free fatty acid and TNF-α circulating levels and of lower levels of adiponectin: this increases both insulin resistance and circulating levels of free fatty acids. The raised fat deposition in the liver induces insulin resistance by itself, activating abnormal insulin intracellular signals. Both these processes lead to an increased hepatic insulin resistance and deposition of fatty acids.

These events, in turn, cause a dysregulation of some sterol regulatory proteins (SREBP-1C) and, probably, of ghrelin. This pathogenic mechanism is responsible for inducing a de novo lipogenesis in the liver.

Thus, it is well evident that NAFLD is a complex and multifactorial disease, and it is currently the most common cause of liver disease and high enzyme levels in clinical practice. Probably a state of IR plays critical part in both the development and progression of the liver disease. It seems that an important role is assumed by oxidative stress and some adipokines, such as TNF-α and adiponectin. Moreover, the nature of the epidemic NAFLD, as well as its clear association with obesity and metabolic syndrome, makes the altered lifestyle and a sedentary lifestyle conditioning factors in the development of this disease even in teenagers [187].

Even if liver biopsy is the “gold standard” for distinguishing between simple steatosis and NASH, and for disease severity assessment, the diagnosis of fatty liver is clinically performed by ultrasound:

1.

2.

3.

4.

The extent of steatosis is related to the degree of insulin resistance [188].

Elevated liver enzymes have been used as a noninvasive surrogate marker of NAFLD, provided that other potential causes of liver disease (chronic viral hepatitis, alcohol-induced liver disease, etc.) have been excluded.

The typical pattern of abnormal liver biochemical profile includes increased serum aminotransferases, with a predominant increase of alanine aminotransferase (ALT), relative to aspartate aminotransferase (AST), accompanied by elevated γ-glutamyl transpeptidase levels (γ-GT) [189, 190].

Elevated ALT, above the level of 35 U/l, has been detected in 30 % of overweight/obese PCOS women [191, 192].

Both adult and pediatric patients with NASH are commonly asymptomatic. Rarely, patients may present with persistent right upper quadrant pain or chronic pain in the umbilical region. On physical examination, more than 90 % of patients with NASH are found to be obese, and acanthosis nigricans has been reported in 36–49 % of patients [193].

A number of studies have demonstrated a high risk of hepatic steatosis in women with PCOS [187, 192, 194–196].

A recent study has shown that women with hyperandrogenic PCOS have evidence of increased liver fat, compared with PCOS women with normal androgens or with healthy controls [197].

In one of our studies, an elevated percentage of NAFLD both in lean and obese women, with a low rate of hepatomegaly (8.3 %) and 15 % of elevated liver enzymes, was found. In fact, liver enzyme impairment is not always associated to the presence of NAFLD, and vice versa [187].

Moreover, in contrast to what happens in other population subgroup where only a minority of patients who suffer from NAFLD progress to NASH, the prevalence of advanced liver disease (NASH with fibrosis) in women with PCOS is higher [192, 198] even in the adolescent population [199].

For these reasons, from a clinical point of view, it seems advisable to closely follow women with PCOS and insulin resistance, particularly in the presence of body weight alterations.

3.2.3.4 Hypertension

Hyperinsulinemia may contribute to the hypertension (which is part of the metabolic syndrome) by several mechanisms:

· Stimulating the renin–angiotensin–aldosterone system and consequently increasing renal sodium reabsorption [200, 201]

· Causing an increased intracellular sodium and calcium [202]

· Inducing vasoconstriction by stimulation of the sympathetic nervous system [203–205]

· Stimulating the release of IGF-1 that may contribute to the development of hypertension by causing vascular smooth muscle hypertrophy [137]

The prevalence of hypertension in PCOS women increases with BMI as independent factor [206].

Women with PCOS were found to have an increased left atrial size and left ventricular mass index, with a reduced left ventricular ejection fraction [207], which is directly related to the degree of insulin resistance; this finding may represent early remodeling as a prelude to overt cardiac dysfunction [208].

The results of many studies are controversial: in a few of them, both systolic and diastolic blood pressures are normal [124, 209–212], while in other studies, mean arterial pressures and ambulatory systolic pressures are elevated in women with PCOS compared with non-PCOS controls [212].

PCOS patients appear to be at increased risk for developing hypertension, at least later in life if it doesn’t occur during the reproductive age.

For menopausal or climacteric women with a previous history of PCOS, this prevalence varies from 28.1 to 39 % [209, 213], while for patients who are in their third or fourth decades of life, the prevalence varies from 3.8 to 22 % [213–215].

This difference of prevalence according to the age range is probably a consequence of aging itself.

3.2.3.5 Diabetes

PCOS women are at high risk of progression to impaired glucose metabolism and type II diabetes; a family history of type II diabetes is present in a large percentage of women affected by PCOS, suggesting the important role of the genetic pattern in the development of the syndrome.

Generally, glucose levels remain normal in PCOS despite insulin resistance, because of compensatory pancreatic β-cell insulin production resulting in hyperinsulinemia. However, some patients have a genetic susceptibility to pancreatic β-cell failure and, over time, develop elevations in glucose when pancreatic β-cell insulin production can no longer overcome the insulin resistance [216].

A study reported that 35 % of patients with PCOS had impaired glucose tolerance (IGT) and 10 % had type II diabetes (T2DM) by the age of 40 [217].

A very recent study showed that the conversion rate from IGT to T2DM in women with PCOS was higher than that in the general population of women with IGT: 2–10.75 % vs 1–7 % per year [218].

Moreover, it was clearly shown that the risk for IGT or T2DM in women with PCOS was amplified (fourfold increase) in the presence of obesity, highlighting the role of patient weight in the development of glucose metabolism disorders [218].

A Korean study found that nonobese patients with PCOS presented a higher prevalence of elevated glycated hemoglobin than nonobese controls [219].

Both IGT and T2DM are very significant cardiovascular risk factors in women. Once the diagnosis of diabetes is made, the relative risk of cardiovascular disease in women increases fourfold to sevenfold, with a greater risk of cardiovascular disease and heart failure compared to men with diabetes [220].

With regard to mortality rates, diabetes may be a more prominent contributing cause of death in women with PCOS compared with the general population [221].

3.2.3.6 Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a known cardiovascular risk factor and is one of the major causes of chronic sleep disruption. It is characterized by episodic partial or complete upper airway obstruction during sleep, leading to intermittent hypoxia, sleep fragmentation, and a reduction in the quantity of deep non-rapid eye movement (NREM) sleep or “slow wave sleep” (SWS). This alteration has been associated with cortisol levels rising [222].

OSA has been independently related to glucose intolerance and insulin resistance even after adjustments for obesity and age [223–227], and PCOS women are 5–30 times more likely to have this disorder compared to controls [167, 176, 228–231].

The mechanism by which PCOS increases the risk of OSA remains unclear.

The high prevalence of this disorder cannot be fully attributed to excess adiposity, as reported in some studies: in two studies the severity of OSA did not correlate with BMI [229–231], and in another one, even after controlling for BMI, women with PCOS were 30 times more likely to have breathing disorders during sleep and 9 times more likely to have daytime sleepiness than the control women [230].

On the other hand, according to a recent study, nonobese women with PCOS do not seem to be at increased risk of OSA: this raised risk is only present among the obese women [232]. Other studies have also indicated that obese women with PCOS who have OSA are more insulin resistant compared to obese women with PCOS who do not have OSA [231, 233, 234].

Insulin resistance, in fact, seems to be a stronger predictor of OSA, more than age, BMI, or circulating testosterone concentration [229]: the role of androgen elevation in the pathogenesis of OSA in women with PCOS remains controversial [229, 230].

Another potential pathogenic mechanism is the “low progesterone theory”: it has been estimated that the upper airway resistance is lower during the luteal phase, when usually progesterone is higher, compared with follicular phase when progesterone is low [235]. Progesterone promotes its effects through direct stimulation of respiratory drive [236] and enhancement of the upper airway dilator muscle activity [237] by which it reduces airway resistance. Because women with PCOS have usually anovulatory cycles, and so circulating progesterone concentrations reflect the constantly lower levels of the follicular phase, this may contribute to the high prevalence of OSA in PCOS [238].

3.2.3.7 Plasma Viscosity and Pro-thrombotic State

In healthy individuals, there is equilibrium between the hemostatic coagulation and fibrinolytic systems: thrombosis results from an imbalance between these complex systems [239]. The hemostatic system plays an important role in cardiovascular disease: for example, acute events often precipitate by thrombosis developing on a ruptured arterial plaque.

Plasma viscosity is an important hemorheologic variable, and it is mainly determined by several macromolecules, such as fibrinogen, immunoglobulins, and lipoproteins [240].

Plasma viscosity is an indicator of blood flow in the network of small blood vessels that constitute microcirculation. An elevated plasma viscosity indicates increased resistance to blood flow in most tissues of the body [241].

Chronic hyperviscosity is able to impair microcirculation and promote target organ damage [242], and it is considered an independent predictor of cardiac events and mortality [243–245].

In a recent study, plasma viscosity is not connected to serum androgen levels, but it is correlated with serum fasting insulin and cholesterol levels, which appear to be higher in hirsute women compared to the matched for age and BMI healthy controls [246, 247].

Mild or chronic hyperviscosity is very frequent in older patients with metabolic syndrome (MS) and insulin resistance (IR) [248–250]. A deterioration of plasma viscosity was found to be present even in young, slightly overweight, PCOS women with IR who might be exposed to the same risk factors for cardiovascular diseases as older obese patients with MS. For this reason, plasma viscosity might be useful in the assessment of cardiovascular risk in young women with PCOS, in addition to plasma cholesterol and atherogenic index (triglycerides/HDL-C) [247].

Hyperinsulinemia contributes to the pro-thrombotic state by reducing fibrinolysis and raising the level of PAI-1 (plasminogen activator inhibitor-1). The increase of the latter in PCOS women seems to be independent of BMI: elevated levels, in fact, were observed in lean PCOS women too [137].

The procoagulant state is, in part, due to platelet hyperactivity, which was observed in lean women with PCOS [251] and in type II diabetic patients [252]. Why?

Platelets are involved in acute thrombosis, initiation of atheroma, and modulation of inflammatory responses, and they contribute to endothelial dysfunction [253]. Platelets are able to adhere to intact activated endothelium in the absence of exposed extracellular matrix proteins [254]. These adherent platelets could have a critical role in atherogenesis phenomenon, by secreting chemokines CCL5, CXCL4, and IL-1 [255].

Normally, platelet activation is counterbalanced by inhibitory signaling cascades that are activated by endothelial-derived NO and prostacyclin (PGI2), which modulate excessive activation [256].

Platelet hyperactivity seems to be related to acute hypertriglyceridemia: in fact, high levels of triglycerides might decrease the production of endothelial NO and PGI2, acting as a stimulator of platelet activation [257].

3.2.3.8 Chronic Inflammation, Endothelial Function, and Atherosclerosis

The presence of cardiovascular risk factors such as obesity, insulin resistance, and dyslipidemia may predispose PCOS women to coronary heart disease, but the topic is still controversial [137].

One of the early signs of cardiovascular lesions is the endothelial injury [258]. Several authors have reported precocious anatomical and functional arterial changes in PCOS women [259–261].

A positive correlation was demonstrated between abnormal endothelial function and testosterone levels in hyperandrogenic insulin-resistant women [262], while others have reported no differences for increased cardiovascular risk [263].

Mechanisms involved in the development of endothelial dysfunction could be the following:

· Reduced synthesis and release of nitric oxide (NO) [264].

· Enhanced inactivation of NO after its release from endothelial cells [265].

· Enhanced synthesis of vasoconstricting agents [266].

· Insulin itself acts directly on the vascular endothelium and the smooth muscle cells by a hypertrophic effect.

Insulin stimulates both endothelin-1 and NO activity in the skeletal muscle circulation: an imbalance between the release of these factors may be involved in the pathophysiology of endothelial dysfunction.

In normal women, aging per se is associated with progressive attenuation of nitric oxide signaling; in PCOS women, these changes are present in early adult life, predisposing polycystic ovarian syndrome patients to premature atherosclerosis; in fact, high levels of plasma ADMA were found: endogenous NO synthase inhibitor N^G-N^G-dimethyl-L-arginine (ADMA) is a biochemical marker/mediator of endothelial dysfunction [267].

Furthermore, the important role of obesity in the mechanism of endothelial dysfunction in PCOS women was shown: in humans, adiponectin enhances endothelium-dependent and endothelium-independent vasodilatation, reduces levels of TNF-α, and diminishes its effects on endothelial cells [268, 269]. This, in turn, reduces neointimal thickening and proliferation of smooth muscle cells, inhibits endothelial cell proliferation and migration, inhibits endothelial effects of oxidized LDL, and attenuates growth factor effects on smooth muscle cells [270–273].

Nowadays, it is clear that PCOS is a pro-inflammatory state, and emerging data suggest that chronic low-grade inflammation supports the development of metabolic aberration and ovarian dysfunction [274, 275].

CRP is the most reliable circulating marker of chronic low-grade inflammation in PCOS [276]. Recently, CRP was found to be a direct promoter of the atherosclerotic processes and endothelial cell inflammation leading to atherothrombosis [137].

CRP has a direct role in the vascular inflammatory process stimulating the release of inflammatory cytokines and increasing endothelial expression of cellular adhesion molecules, which mediate leukocyte migration [277].

Findings of a study suggest that increased cardiovascular risk may be seen in 83.3 % of the PCO women with CRP >2.42 mg/l [278].

CRP values <1 mg/l are considered low risk, 1–3 mg/l are considered intermediate risk, and 3–10 mg/l are considered high risk for cardiovascular disease [279].

Anatomic evidence of early coronary and other vascular diseases in PCOS women has been reported: it seems that PCOS patients have increased carotid artery intima-media thickness (IMT) compared with age-matched control women [280].

Increased IMT has been linked to cardiovascular risk factors including dyslipidemia and obesity, and it is considered an independent predictor of stroke and myocardial infarction [78].

The role of hs-CRP in predicting increased carotid intima-media thickness is not independent of BMI in PCOS [280].

Coronary artery calcification, another marker of atherosclerosis, is more common in women with PCOS than in controls, even after adjustment for the effects of age and BMI [281–283].

3.2.4 Role of Insulin Resistance in Infertility and Pregnancy Outcome

As pointed out previously, PCOS is the most common cause of anovulatory infertility: 90 % of women attending infertility clinic for anovulation disorder are affected by PCOS, and the rising incidence of PCOS women who have been subjected to IVF had permitted several studies on their oocyte quality.

On the other hand, without considering IVF pregnancies, increased incidence of pregnancy complications such as miscarriage, gestational diabetes mellitus (GDM), preeclampsia, preterm delivery, and perinatal mortality has been reported in polycystic ovary syndrome (PCOS) pregnancies: an increase of two to four times was noticed [284].

3.2.4.1 Oocyte Quality

Obesity has been associated with lower levels of anti-Mullerian hormone (AMH), which can indicate a decrease in ovarian reserve or available secondary follicles in obese women [285]. Obese women also have lower levels of LH than normal-weight women, and an independent positive association between LH and AMH levels has been demonstrated [36]. Moreover, women with BMI >25 have lower excretion of gonadotropins and luteal phase progesterone metabolites, implying that obesity has a negative effect on corpus luteum function [286].

Studies directly examining oocyte quality have suggested that an altered maternal metabolic environment results in an abnormal follicular fluid microenvironment, with a subsequent poor oocyte and embryo quality.

Women with higher BMI had increased levels of insulin, lactate, triglycerides, and CRP in the follicular fluid and decreased levels of SHBG [287], indicating that the maternal metabolic environment has a direct effect on the ovarian follicular microenvironment [288].

The increased CRP in the follicular fluid indicates inflammation and increased oxidative stress, with consequent decreased developmental potential in the oocyte [287, 289]. A recent analysis has showed that obese PCOS women have smaller oocyte size compared with the control group [290], but nowadays the effect of oocyte size on developmental competence and pregnancy outcome is unknown.

3.2.4.2 Recurrent Pregnancy Loss

Recurrent pregnancy loss (RPL) is defined by two or more failed pregnancies and it is found in 1–5 % of couples during pregnancy, and 50 % of these cases remain unexplained [291]. The incidence rate between PCOS and recurrent miscarriage is not clear because of its large variation in different studies [292–295]. Some authors have reported that PCOS women have a 33 % chance of spontaneous abortion [293, 296].

The following are the two most reasonable mechanisms:

1.

2.

On the contrary, other studies did not confirm the association between early pregnancy loss and PCOS [315].

3.2.4.3 Gestational Diabetes

In normal pregnancy, maternal carbohydrate metabolism adapts to offer the fetus an adequate and continuous glucose supply despite intermittent maternal intake. The physiologic changes include pancreatic β-cell hyperplasia and an initial increase in insulin sensitivity followed by a progressive insulin resistance.

β-cell hyperplasia seems to be induced by prolactin and human placental lactogen; on the contrary, production of “diabetogenic hormones,” such as GH and CRH, contributes to insulin resistance. This maternal insulin resistance, in turn, shunts nutrients to the fetus.

From the third trimester, fasting glucose concentrations are 10–20 % lower, postprandial glucose concentrations are significantly elevated and prolonged, and fasting insulin level is double that of nonpregnant women [216].

Thus, normal pregnancy induces a state of insulin resistance, and because women with PCOS have a high incidence of IR, they have an increased risk of developing gestational diabetic complications [316].

GDM is defined as carbohydrate intolerance that either begins in or is first recognized in pregnancy [317]. Its pathophysiology includes both insulin resistance and abnormalities of β-cell glucose sensitivity, which leads to inadequate insulin response [318].

According to a large study, PCOS women have a 2.4-fold increased odds of gestational diabetes, independent of age, race, and multiple gestation [319]. Furthermore, this increased risk occurs independent of obesity [320].

In fact, during the pregnancy, hyperinsulinemic women with PCOS develop more easily impaired glucose tolerance or gestational diabetes: the compensatory mechanism (reduced glucose clearance and/or defects of insulin action at receptor and post-receptor sites) that leads to prepregnancy hyperinsulinemia may more easily fail during pregnancy [321].

Investigators have shown that women with GDM with higher glucose values at OGTT, higher mean blood glucose, and worse glycemic control are at higher risk of preterm delivery [322].

Moreover, it was found that women with PCOS and GDM had a 3.5-fold higher risk for impaired glucose metabolism after delivery [323].

3.2.4.4 Pregnancy-Induced Hypertension

A meta-analysis showed that PCOS women have a higher risk of developing pregnancy-induced hypertension: this risk was also present after excluding all studies in which a higher BMI, multiple pregnancy rates, and a lower parity among women with PCOS were reported. Women with PCOS also demonstrated an increased incidence of preeclampsia of an order similar to that associated with multiple pregnancies. Moreover, older (age >30 years) women with PCOS are more susceptible to PIH than the younger women [324].

As widely explained in the previous chapter, hyperinsulinemia can cause endothelial dysfunction, and this association suggests a placental insufficiency in PCOS women [320], due to a vascular maladaptation: in fact, a study showed that arterial elasticity is impaired during the first trimester, while it decreases during the second and third trimester. It was also reported that systolic, diastolic, and mean arterial pressures were elevated throughout the pregnancy and that 27 % of the women with PCOS developed pregnancy-induced hypertension [325].

Furthermore, hyperandrogenemia in early second trimester and throughout pregnancy is associated with subsequent preeclampsia [326–330], and preeclampsia in a previous pregnancy is associated with elevated androgen levels later in life [330]. In fact, maternal androgen levels are higher in complicated compared to uncomplicated pregnancies in PCOS women [301]. This hypothesis was based on in vitro studies of preeclamptic placentas that were found to have decreased ability to aromatize androgens to estriol, compared to placentas from normal pregnancies [331].

3.2.4.5 Neonatal Outcome

Despite the risk of macrosomia due to the increased risk of gestational diabetes, the prevalence of SGA seems to be increased in PCOS women: 12.8 % vs 2.8 % of healthy controls, according to a Dutch study [332].

The cause can be found in the placental dysfunction or could be influenced by the mild raised number of preterm labor (1.75-fold higher risk).

Neonates of PCOS women have a 2.31 times higher risk of admission to intensive care unit and three times higher perinatal mortality than newborns of healthy women. Perinatal morbidity could be explained by prematurity and intrauterine growth retardation due to the placental dysfunction [333].

3.3 PCOS Phenotype in Different Ages

PCOS clinical and biochemical presentations and its metabolic consequences vary with age (Table 3.1) [334, 335].

Table 3.1

PCOS features in different ages

Adolescence	Fertile period	Perimenopausal period
Chronic anovulation	Periods became more regular	Increased IGT, type II diabetes, hypertension, obesity, metabolic syndrome
Oligomenorrhea/amenorrhea	Increasing levels of insulin resistance

3.3.1 Adolescence

The clinical presentation of chronic anovulation varies by age, with amenorrhea and oligomenorrhea being common among adolescents [336].

Menstrual irregularities and insulin resistance are common and usual features of normal puberty period, and they can make the diagnosis of PCOS in this period of life difficult [337].

Menstrual irregularity is common in the early years after menarche, and oligo-anovulation may be absolutely normal [338]: this is due to the immaturity of the hypothalamic–pituitary–ovarian (HPO) axis. An old study showed that 80 % of the cycles were anovulatory in the first year after menarche, 50 % in the third, and 10 % in the sixth: it is generally accepted that it may take up to 5 years after menarche for the HPO axis to reach maturation [339, 340].

The serum concentrations of sex hormones increase with age, from premenarchal to post-menarchal [339].

Furthermore, concomitant eating disorders are frequent during these ages, and secondary amenorrhea can be associated with anorectic behavior in adolescents [341]. As ultrasound images have shown, uterine growth continues several years after menarche, and the average ovarian volume increases from early childhood until the age of 16 [342].

Regarding the ovarian morphology, the difference between a multifollicular appearance and polycystic ovarian morphology in adolescents is difficult to define [342]. About 80 % of girls have this USS finding and the presence of polycystic ovarian morphology in a non-hyperandrogenic adolescent should be considered normal [343].

Mild hair growth can be also considered a normal component of the late stages of puberty and early adolescence, because it can persist for several years; therefore, the diagnosis is often not made until later in life, when endocrine and metabolic dysfunctions have been firmly established [344].

In fact, the most important finding for clinical hyperandrogenism in female adolescents is progressive hirsutism [344]: acne and alopecia were not suggested as clinical markers for the diagnosis of PCOS in adolescents [345].

Premature pubarche, or the development of pubic and axillary hair before age 8 years, may be an early sign of PCOS [346]. Premature pubarche may occur as a result of some adrenal androgen disorders, but it could also be due to an idiopathic early activation of adrenal androgen secretion. However, not all girls with PCOS experience premature adrenarche; persistent hyperandrogenism remains a distinct feature of girls with premature pubarche who go on to develop PCOS, and the hyperandrogenism is exacerbated if a child develops obesity [347].

On the other hand, puberty period is normally associated with a mild insulin resistance: this is called “physiological peri-pubertal hyperinsulinemia,” which together with increased GH levels is responsible for the “pubertal growth spurt”; the result is an accelerated bone, muscle, and adipose tissue growth.

Moreover, adolescent hyperandrogenemia is associated with a reduction in peripheral tissue insulin sensitivity and compensatory hyperinsulinemia, which implies an increase in the risk of type II diabetes [348]. The increased prevalence of obesity in the younger population leads to long-term consequences for cardiovascular disease at relatively young ages.

There is a strong inverse relationship between reported age and weight at menarche, suggesting that girls who were overweight had an earlier menarche, while those who were thin, compared with their peers, experienced a later menarche [349].

Earlier menarche in girls with PCOS might be expected based on findings that overweight girls experience earlier pubarche, thelarche, and menarche than those with a normal BMI [350, 351].

According to all these findings, a definitive diagnosis of PCOS in adolescents should require all three Rotterdam elements (not just 2 out of 3) [345].

3.3.2 Fertile Period

PCOS remains stable only during early adult age (18–30 years), but after that time, it changes in ovarian and adrenal function and in metabolic regulation modifying the presentation of the syndrome [352].

The menstrual cycles may become regular with age in women with PCOS [353, 354]: the development of a new balance in the polycystic ovary, caused merely by follicle loss through ovarian aging, can explain the occurrence of regular cycles in older patients with PCOS [354]. In a study of aging women with PCOS comparing those who became regular with those still menstruating irregularly, a lower follicle count for women with PCOS was predictive of the achievement of regular menstrual cycles with age [355], confirming that a decrease in the size of the follicle cohort from ovarian aging is largely responsible for the regular menstrual cycles in aging PCOS women [355]. The decrease in both ovarian volume and follicle number, caused by the aging, results in loss of PCO morphology [356].

The production of androgens in women may decrease because of ovarian aging or decreased production by the adrenal glands over time [357].

Normally, there is a marked decrease in adrenal androgen secretion, including androstenedione and DHEAS, between the ages of 40 and 45 years [358]; androgens levels also decline 20–30 % in women with PCOS.

A recent study, consisting in a 20-year follow-up of PCOS women, showed the inability to diagnose the disorder in about 10 % of women who had PCOS diagnosed 20 years earlier [359].

3.3.3 Premenopausal and Postmenopausal Period

Hyperandrogenism partially resolves before menopause in women with PCOS [360], but a recent study showed that adrenal androgen secretion also remains pronounced up to menopause in women with PCOS, indicating that exposure to hyperandrogenism persists for a long time in these women [361]: they have an elevated androgen to estrogen ratio.

It seems probable that long-lasting hyperandrogenism may magnify the unfavorable hormonal and metabolic changes related to menopause and expose these women to increased health risks [362].

Ovarian volume and follicle number decrease with age in women with and without PCOS [363].

AMH levels decreased with an increase in age in both the PCOS cases and normo-ovulatory controls [364]. AMH measurement could be useful in the prediction of the menopausal transition [365, 366]. Using AMH as a predictive marker, the reproductive lifespan of PCOS women is an average of 2 years longer than that of normo-ovulatory women [364].

Furthermore, aging may also be associated with a defect in insulin action [367]. In fact, age is an important risk factor for developing metabolic disorders and insulin resistance. Aging may also be associated with a defect in insulin action that is manifested by decreased whole-body tissue sensitivity to insulin without a change in tissue responsiveness [367]. The glucose intolerance may reflect part of the aging process. In elderly subjects, the severity of carbohydrate intolerance is directly correlated with the degree of peripheral insulin resistance [368].

A recent study has demonstrated that impaired glucose metabolism, enhanced ovarian androgen secretion, and chronic inflammation observed in premenopausal PCOS women persist after menopause [362].

As result, it is clearly noted that the most common symptoms in senior age are those related to metabolic syndrome.

Despite the longer exposure to cardiovascular risk factors, it is still difficult to demonstrate an increased risk of morbidity and mortality in women with PCOS: only two studies tried to study PCOS long-term outcomes, but no increased cardiovascular morbidity or raised risk of death, up to age 70 years, was pointed out [221, 369].

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