Ariel Revel1 and Jordana Hadassah Hyman1
(1)
Department of Obstetrics and Gynecology, The Hadassah University Hospital-Ein Kerem, 12000, Ein Kerem, Jerusalem, 91120, Israel
Jordana Hadassah Hyman
Email: jordana@hadassah.org.il
Abstract
Endogenous androgens, which are synthesized in the adrenal glands and the ovary, play a crucial role in folliculogenesis. Androgens undergo aromatization into estrone and estradiol in the granulosa cells. Androgens also exert an influence on the follicular cycle, acting via granulosa cell receptor to FSH.
In states of androgen excess, there is usually a high number of antral follicles and enhanced response to gonadotropin therapy. This has led to the hypothesis that increasing intraovarian androgen, either via exogenous testosterone administration or by increasing local ovarian testosterone concentration, can potentially increase the quantity and quality of oocytes retrieved during controlled ovarian (hyper)stimulation (COS) and improve pregnancy and live birth rates.
Women who are poor responders to COS classically have shortened follicular phase, with a smaller window for recruitment of follicles, as well as reduced sensitivity to FSH. Poor responders may exhibit improved response to treatment with the addition of exogenous testosterone, as well as adjuvant LH administration, which can increase endogenous androgens. Treatment options include transdermal testosterone, DHEA, aromatase inhibitors, and adjuvant LH.
Aromatase inhibitors, which block aromatization of androstenedione and testosterone to estrone and estradiol, are also used in COS in women undergoing treatment for fertility preservation. In these cases, it is desirable to preserve low estradiol levels. The addition of aromatase inhibitor also reduces the required gonadotropin dosage.
Current research and meta-analyses regarding androgen therapy in COS are presented in this chapter, as well as clinical application and recommendations.
Keywords
Androgen therapyPoor respondersControlled ovarian stimulationTestosteroneDHEAAromatase inhibitor
15.1 Rationale for Androgen Therapy
Folliculogenesis is the process of development of primordial follicles into primary, pre-antral, and then antral follicles, which are then recruited in the menstrual cycle. A dominant or preovulatory follicle is selected and undergoes follicular rupture with ovulation of the oocyte, while the rest become atretic. The follicular cycle is influenced by a complex interplay between FSH, LH, inhibin, activin, and follistatin. FSH and LH synthesis and secretion are regulated by GnRH, with negative feedback from estrogen and progesterone. These hormones control the recruitment of follicles, selection of the dominant follicle, timing of ovulation, and luteal phase. In most spontaneous cycles, a single oocyte is ovulated per cycle [1–5].
Controlled ovarian stimulation (COS) involves exogenous hormonal stimulation of the ovaries in order to recruit and develop multiple dominant follicles, enabling retrieval of several oocytes with potential for fertilization [6, 7]. Traditional protocols for COS include stimulation with gonadotropins, combined with prevention of premature ovulation by either downregulation with GnRH agonist (long protocol) or concurrent treatment with GnRH antagonist (short protocol) and control of the timing of ovulation by either mimicking (hCG) or inducing (GnRH agonist) the endogenous LH surge [8]. Endogenous androgens, which are produced in both the ovary and the adrenal glands, also have an important role in follicular development. According to the two-cell two-gonadotropin theory, follicular steroid hormones synthesized in the theca cells – androstenedione and testosterone – undergo aromatization into estrone and estradiol in the granulosa cells [9]. Androstenedione and testosterone are synthesized from cholesterol, with dehydroepiandrosterone (DHEA) as a steroid precursor [10, 11]. DHEA is mainly synthesized in the adrenals. Androgen production in the ovary is regulated by FSH, LH, and inhibin.
In addition to acting as a substrate for estrogen production, androgens also influence the follicular cycle [12–16]. They appear to act via granulosa cell androgen receptors (ARs) to promote FSH-induced granulosa cell differentiation and may enhance the follicular response to FSH, particularly in early antral stages of folliculogenesis [17]. Androgen receptor mRNA and androgen concentrations in follicular fluid are correlated with FSH receptor mRNA expression in granulosa cells from small antral follicles [18, 19]. Androgens may also increase the number of FSH receptors expressed in granulosa cells. Immunohistological staining of androgen receptors during different times of the menstrual cycle showed varying intensities during the cycle, with strongest expression during the antral to preovulatory phase, suggesting that androgens, mediated by androgen receptors, may play an essential role in follicular growth and maturation, atresia, and luteinization [20]. FSH receptor expression can be modulated by testosterone added to granulosa cells [21].
Women with excessive androgens, either in cases of ovarian hyperandrogenism such as polycystic ovarian syndrome (PCOS); adrenal hyperandrogenism, such as congenital adrenal hyperplasia; or exogenous androgen treatment, such as testosterone-treated transsexuals, have a high number of antral follicles [13, 22, 23]. While the hyperandrogenism often is associated with dysovulation or anovulation, such women are usually extremely sensitive to low doses of exogenous FSH stimulation. In ovarian stimulation cycles, the addition of exogenous androgens may affect the hormonal milieu of the ovary, by increasing the number of small antral follicles and improving the follicular sensitivity to FSH [24]. This could potentially enhance the ovarian response to stimulation and lead to better reproductive outcome, especially in women who are poor responders. Androgens may also stimulate follicular steroidogenesis via IGF-1 and IGF-2 stimulation and IGFBP1 inhibition [25–28].
Increased circulating insulin and IGF-I, exogenous testosterone, and increased local ovarian testosterone concentrations due to aromatase inhibition or exogenous luteinizing hormone/human chorionic gonadotropin are all associated with an increased ovarian response to gonadotropins.
The hypothesis underlying androgen use in ovarian stimulation is that increasing intraovarian androgens, either via exogenous testosterone administration or increased local ovarian testosterone concentrations due to aromatase inhibition or exogenous LH/hCG, would result in an increase in the number, maturity, and reproductive potential of the oocytes.
15.2 Patients with Potential Benefit from Androgen Therapy
15.2.1 Poor Responders
During physiological reproductive aging, the primordial follicle count declines rapidly [29]. This is associated with decreased oocyte quality, increased aneuploidy, and reduced fertility and fecundity [30, 31]. The associated diminished ovarian reserve and reproductive potential is usually age related, but can be accelerated in certain women. Poor responders to ovarian stimulation include women with decreased ovarian response due to physiological age, as well as those with accelerated reproductive aging, due to a variety of etiologies, such as genetic or immunologic premature ovarian failure, endometriosis, malignancy, or exposure to gonadotoxic agents.
There is no universal agreement regarding the definition of poor responder. The Bologna criteria, described in 2011 [32], however, represent the ESHRE consensus. This defines poor responders as women with at least two out of the three following criteria: (i) advanced maternal (age ≥40 years) or any other risk factor for poor ovarian response, (ii) a poor ovarian response (≤3 oocytes with a conventional stimulation protocol), and (iii) an abnormal ovarian reserve test result (i.e., AFC < 7 follicles or AMH <1.1 ng/ ml).
15.2.1.1 Poor Responders: Treatment Options
Many treatment options for poor responders have been proposed and evaluated. The most recent Cochrane review of interventions for poor responders [33] concluded that there was insufficient evidence to support any particular treatment protocol or adjuvant treatment. However, a review of randomized trials of interventions for poor responders performed in 2011 [34] showed that in 47 trials there were 41 different definitions of poor ovarian response. It is challenging to interpret and compare data from trials performed before the Bologna criteria, which offers a standardized definition of poor responders, and difficult to exclude potential benefit of any options for treatment. It is also difficult to perform randomized controlled trials on this group of women.
Treatment for poor responders includes both specific ovarian stimulation protocols and adjuvant therapy [35–37]. Ovarian stimulation protocols that have been proposed include natural cycle IVF, minimal stimulation IVF, minimal stimulation with aromatase inhibitor (letrozole), short or antagonist protocol, and microdose flare protocol. There is also much debate regarding the dose and type of gonadotropin. High or very high dose? Single dose or multiple doses? FSH plus LH? Purified gonadotropins? No single treatment protocol has been proven.
Many adjuvant therapies have been proposed by both medical and alternative practitioners. These include growth hormone [38–41], androgens including DHEA and testosterone, arginine [42], glucocorticoids, pyridostigmine, and aspirin [43]. More recently, COQ10 has been advocated for poor responders [44]. Acupuncture has also been promoted for poor responders. Intracytoplasmic sperm injection (ICSI) and assisted hatching are laboratory techniques which may increase pregnancy rates in older women or poor responders.
15.2.1.2 Poor Responders: Rationale for Androgens
Poor responders typically have shorter or irregular cycles, with a shortened follicular phase. This shortens the potential window for recruitment of follicles. An additional challenge is reduced sensitivity of FSH receptors, which leads to the use of very high gonadotropin doses in this patient group. Women with poor response to gonadotropins exhibit lower expression of FSH receptor granulosa cells [45, 46].
Exogenous androgen therapy causes an increase in follicular levels of testosterone and androstenedione, as does treatment with aromatase inhibitor [27, 47], which acts as a mediator by blocking aromatization to estrogens and thus effecting an endogenous increase. LH administration in addition to FSH also causes increased endogenous androgen production and is also recommended for poor responders [48, 49]. Increased intraovarian androgens have been reported to increase follicle numbers, increase antral follicle count [50, 51], improve follicular survival, reduce apoptosis/atresia, and enhance IGF-1 concentration [52, 53]. The outcome of this improved follicular microenvironment includes increased quantity and superior quality of oocytes available for fertilization, with improved fertilization, reduced cancellations, improved pregnancy and live birth rates, and decreased aneuploidy and miscarriage rates. It has been postulated that low pregnancy rates and embryo aneuploidy may result from low intrafollicular androgens; adjuvant androgen therapy may serve to rectify this deficiency [54–57].
15.2.1.3 Hypoandrogenism in Poor Responders
Adrenal and ovarian androgen levels undergo changes during reproductive aging and menopause, with a natural decline commencing as early as age 30 [58, 59]. Follicular levels of testosterone have been shown to be reduced in poor responders who underwent COS, as compared with normal responders [60, 61]. The number of zona reticularis cells, the site of DHEA synthesis in the adrenal gland, also undergoes decline with reproductive aging and in poor responders [57]. Conversely, De Los Santos [62] reported similar intrafollicular androgen levels in poor responders compared with fertile women. The authors suggested that follicular androgen secretion does not seem to be reduced; rather, other mechanisms such as lower FSH receptor expression or aromatase activity insufficiency may be the main challenges in poor responders.
Basal testosterone has been proposed as a potential marker for poor ovarian reserve. Low basal testosterone and DHEAS are associated with decreased ovarian sensitivity to FSH, reduced response to stimulation [63], and low pregnancy rates after IVF. In women with high FSH, low basal testosterone may be predictive of expected number of large follicles and oocytes, as well as pregnancy outcome [64]. Gleicher [65] suggested that older women with poor ovarian reserve, who have been treated with DHEA supplementation, also show low conversion rates of DHEA to testosterone. The authors present an association between the potential benefit of DHEA supplementation in improving pregnancy rates and the conversion rate of serum DHEA to testosterone, which may serve as a marker in poor responders.
Recently Guo et al. [66] analyzed basal testosterone as a predictor of poor ovarian response and found that it was a predictor but, used alone, had limited use. This study proposed a multivariate model for prediction of poor ovarian response, which included age, AFC, FSH, FSH/LH, and testosterone. Ratios of androgen to AMH and androgen to FSH may also be useful markers for poor response [61]. The use of basal testosterone as a marker for poor ovarian reserve, combined with the declining ovarian and adrenal androgens observed in reproductive aging, implies a need for androgen supplementation in these women.
15.2.2 Fertility Preservation
Women of reproductive age who must embark on potentially gonadotoxic chemotherapy and radiotherapy for treatment of malignancy are another group that may benefit from androgen therapy as part of ovarian stimulation. Chemotherapy can damage or destroy the primordial ovarian follicles, including oocytes and granulosa cells, which can render the woman with premature ovarian failure [67]. Radiotherapy can cause various insult and damage to the reproductive organs, depending on the exact location and dosage of radiation [68]. As more clinicians are aware of fertility preservation options, and as cancer detection and treatment continue to improve, there continue to be more women seeking fertility preservation before cancer treatment.
Depending on the woman’s age and status, the desired fertility preservation technique may be oocyte or embryo cryopreservation or ovarian tissue cryopreservation. Oocyte harvesting involves ovarian stimulation and retrieval. The ovarian stimulation protocol will depend on the actual malignancy, as well as the window of time available prior to commencement of chemotherapy or radiotherapy. Women with breast cancer, particularly estrogen receptor-positive disease, should not be exposed to high levels of estrogen, for fear of cancer recurrence. Therefore, natural cycle IVF or stimulation in combination with aromatase inhibitor may offer the only options for these women.
15.2.2.1 Rationale for Aromatase Inhibitor in Fertility Preservation
Aromatase inhibitors block the aromatization of androstenedione and testosterone to estrone and estradiol, causing higher androgen levels, but suppressed plasma estradiol, estrone, and estrone sulfate levels. The lower levels of estrogen are clearly desirable in women with breast cancer, and these drugs, specifically letrozole and anastrozole, are used as treatment for breast cancer itself, not only for fertility preservation.
Aromatase inhibitors, most commonly letrozole, may be used itself as a form of ovulation induction or in combination with gonadotropins as part of COS [69, 70]. The suppression of estradiol caused by aromatase inhibitors leads to negative feedback, with resultant increased gonadotropin stimulation. Both letrozole only and letrozole-gonadotropin cycles result in very low serum estradiol. However, the addition of letrozole appears to reduce the number of oocytes retrieved for preservation [71]. Aromatase inhibitors used in combination with gonadotropin for ovarian stimulation for fertility preservation have been demonstrated to have significantly lower estradiol levels [72]. They also decrease the amount of gonadotropin required for stimulation [69]. Surveillance after letrozole-gonadotropin ovarian stimulation protocols revealed no negative effects on survival, with no difference in recurrence rate or relapse-free survival [73, 74]. Letrozole has been compared with alternative aromatase inhibitors (anastrozole) [72, 75] as well as to selective estrogen receptor modulators (tamoxifen) [70] and found to be superior for fertility preservation cycles in terms of maintaining low estradiol levels and achieving higher oocyte and embryo yields.
15.3 Androgen Therapy: Options
There are several options including exogenous androgens such as transdermal testosterone and oral DHEA, as well as aromatase inhibitors, which modulate androgen levels.
15.3.1 Transdermal Testosterone
Transdermal testosterone as an adjunct to conventional IVF for poor responders was reported by both the French [76] and Spanish [77] groups in 2006. These studies were based on the hypothesis that androgens act synergistically with FSH receptors and may improve small follicle recruitment and sensitivity to FSH, in poor responders. Balasch [77] enrolled women with two previous failed cycles, who had normal basal FSH levels. All women [25] underwent long GnRH agonist cycle and received 5 days of transdermal testosterone before gonadotropin stimulation was commenced. In comparison with the previous cycles, there was significant improvement in peak E2 levels, number of follicles (>10 mm), number of oocytes retrieved, and clinical pregnancy rate.
Massin et al. [76] reported a randomized controlled trial of poor responders, who either had a previous IVF cycle with poor response (defined as peak E2 of <1,200 pg/ml or <5 oocytes retrieved) or who had basal hormonal profile suggestive of decreased ovarian reserve. Women were randomized to transdermal testosterone gel or placebo. Women were treated with the gel for 15 days prior to gonadotropin stimulation. Although serum testosterone increased significantly in the treated group, there were no significant differences in ovarian response or treatment outcome.
Balasch and Fabregues [78] also performed a randomized controlled study of transdermal testosterone, published in 2009. These were women who had undergone cancellation of their first IVF cycle due to poor response. Patients were randomized to pretreatment with 5 days of transdermal testosterone, in addition to standard long protocol (starting dose 150 U) or mini-dose agonist protocol with high-dose gonadotropin (300 U). More women in the testosterone group achieved oocyte retrieval, and significantly fewer women in the testosterone group were considered low responders in the study treatment cycle. The authors suggest that transdermal testosterone may improve ovarian sensitivity to FSH and follicular response to gonadotropin; however the study had low power to determine significant differences between the study groups. Kim et al. [79] randomized 110 poor responders (<3 oocytes retrieved in the previous cycle) to treatment with transdermal testosterone or control, in conjunction with multidose GnRH antagonist treatment. They reported significant improvement in number of oocytes retrieved, mature oocytes, fertilized oocytes, and good-quality embryos, as well as implantation rate and clinical pregnancy rate per number of women treated with testosterone.
15.3.2 DHEA
Dehydroepiandrosterone (DHEA) supplementation is the other form of adjuvant androgen therapy promoted for poor responders. DHEA is recommended by over 25 % of IVF practitioners, according to the 2010 survey [80]. DHEA treatment was initially reported by Casson in 2000, with a small case series of five poor responders, following their experience with DHEA for postmenopausal women [81]. Later, Gleicher reported the case of a 43-year-old patient, who self-treated with DHEA, improving her oocyte yield from a single oocyte in her first cycle to a maximum of 17 oocytes [82]. This case inspired the interest in investigating DHEA use for poor responders. Barad and Gleicher [83] then reported a case-control study of 25 women, showing increased quantity and quality of embryos in IVF cycles following DHEA treatment. They further reported higher pregnancy rates [84], decreased miscarriage rates [54], and reduced aneuploidy [55] following DHEA administration. Increased number of oocytes, number and quality of embryos, and pregnancy rates, in IVF cycles after DHEA, have been reported in several studies [85–91]. Increased spontaneous pregnancies [84, 92] as well as pregnancies following IUI treatment have been reported in poor responders after DHEA treatment, while waiting for further IVF treatment. They reported 10 spontaneous pregnancies in 39 young (<39 years) women treated with DHEA.
Several studies have also reported improvements in ovarian reserve including reduced FSH [85, 89, 93] and increased AMH [89, 93, 94], as well as increased AFC [88, 93, 95] and inhibin B [93] after DHEA. There have been three randomized controlled trials (RCTs) published to date regarding DHEA supplementation. Wiser [86] reported an RCT of 33 poor responders undergoing long protocol. They noted significantly improved embryo quality and live birth rate in women treated with DHEA. Clinical pregnancy rate was improved, but this was not statistically significant. Kara performed an RCT with 208 women, but concluded that there was no clear evidence of benefit with DHEA [96]. The number of oocytes retrieved and the fertilization rate were slightly higher in the study group, but the pregnancy rate was higher in the control group. None of the differences were statistically significant. The most recently published RCT by Yeung [95], of 32 women randomized to DHEA or placebo, reported no difference in markers of ovarian reserve, response to treatment, or treatment outcome.
Reviews of DHEA use for poor responders have yielded conflicting conclusions. Gleicher and Barad [56] summarized the benefits of DHEA supplementation – improved ovarian function, increased pregnancy rates, and reduced aneuploid and miscarriage rates. They hypothesized that DHEA may be able to revert the ovarian aging process specifically in younger women with premature ovarian failure. However, Urman [97] concluded that there was a lack of evidence to support DHEA. They cited regression to the mean and variability of gonadotropin responsiveness as potential explanations for improvements in treatment cycle and dismissed the only published RCT at that stage as insufficiently designed or powered to allow valid scientific conclusions.
15.3.3 Aromatase Inhibitors
Aromatase inhibitors act by inhibiting the activity of aromatase, which is responsible for conversion of androstenedione and testosterone to estrone and estradiol. This results in higher androgen levels and lowered estradiol, estrone, and estrone sulfate levels. The resultant reduced estrogen feedback causes increased gonadotropin secretion. Aromatase inhibitors, specifically letrozole and anastrozole, were introduced for ovulation induction in women with PCOS who were clomiphene resistant and for women with unexplained infertility [98, 99]. In poor responders, the resultant increase in intraovarian androgens may also be of benefit in a similar mechanism to increased exogenous androgens, with an impact on folliculogenesis, small follicle recruitment, and FSH receptor expression.
Letrozole for poor responders was initially reported in 2002 [100]; treatment with letrozole prior to commencement of gonadotropins led to increased oocyte yield, with lower total dose of FSH. Garcia-Velasco [27] performed an observational pilot study of 147 women with previously cancelled cycles. Women underwent high-dose gonadotropin antagonist protocols, with or without addition of letrozole. The letrozole group showed significantly higher levels of follicular fluid testosterone and androstenedione as well as significantly higher oocyte yield and implantation rate. Pregnancy rate was increased, but not significantly. A large prospective study of 534 women [101] compared microdose flare protocol with a letrozole – an antagonist protocol in poor responders. There were no significant differences in treatment parameters, except that peak estradiol was lower in the letrozole group. Pregnancy rates were found to be significantly higher, with a trend toward improvement of implantation rate in the microdose flare group. Yarali [102] reported a case-control study of 885 poor responders treated with microdose flare or letrozole-antagonist protocols. Total gonadotropin consumption and peak E2 were significantly lower in the letrozole-antagonist group. Oocyte yield was also significantly lower with letrozole treatment, but clinical pregnancy rates were comparable, and fertilization and implantation rates were higher, with more number of top-quality embryos. Lee [103] more recently reported a retrospective study of poor responders treated with multidose antagonist protocol, with or without adjuvant letrozole. Oocyte yield was significantly higher in the letrozole group. Clinical pregnancy, implantation, and miscarriage rates were similar between the groups; however dosage and duration of both gonadotropin and antagonist were significantly lower in the letrozole group. Rate and miscarriage rate were similar in the two groups. Total dose and days of recombinant human follicle-stimulating hormone (rhFSH) administered were significantly fewer in the letrozole group than in the control group.
There have been three randomized controlled trials for letrozole in poor responders. Goswami [104] sought to examine letrozole as a low-cost protocol. Poor responders, with 1–3 previous failed IVF cycles, were randomized to GnRH agonist long protocol or letrozole plus low-dose rFSH protocol (75 IU on days 3 and 8) responders. The letrozole-FSH had comparable pregnancy outcomes, as well as other treatment parameters, and clearly the most cost-effective protocol with considerably less gonadotropin exposure. Omzen [105] randomized 70 poor responders (previous cancellation or low E2 or <4 oocytes retrieved) into fixed-dose (450 IU) rFSH antagonist cycle with and without letrozole. Gonadotropin dose and peak E2 were significantly lower in the letrozole group, as was cancellation rate. Higher clinical pregnancy rate was reported in the letrozole treatment group. Mohsen [106] randomized 60 women with at least one failed IVF cycle (four or less oocytes retrieved) to mild stimulation letrozole-antagonist or microdose flare agonist treatment. Dose and duration of gonadotropin were significantly lower, as was peak E2, in the letrozole group, and clinical pregnancy rate was comparable. Other parameters were comparable between the groups.
15.4 Results of Meta-Analysis Reviews
There has been one meta-analysis specifically examining transdermal testosterone, one meta-analysis regarding DHEA, and two which examine androgen therapy for poor responders. In the review and meta-analysis of transdermal testosterone, Gonzalez-Comadran [107] analyzes the three RCTs previously presented [76, 78, 79], a total of 225 women. It was noted that the inclusion criteria and definition of poor responder was not consistent between the three trials. There was also a variation in the actual treatment protocol and in the regime for application of transdermal testosterone, with different doses and length of treatment ranging between 5 and 21 days. Pooled analysis of the data showed significantly increased clinical pregnancy and live birth rate in the treated group. Clinical pregnancy per transferred embryo, however, proved not to be significantly different between the two groups. Women in the testosterone group required significantly less FSH stimulation than the controls. There was no significant difference detected in other parameters including cycle cancellation rate, peak estradiol, number of oocytes retrieved, or miscarriage rate.
Narkwichean et al. performed a meta-analysis of DHEA for poor responders [108]. Of the 22 studies, only 3 were eligible for meta-analysis – Wiser [86], Gleicher [55], and Barad [84]. Clinical pregnancy rate was assessed by analyzing two studies; no significant difference was demonstrated. There was no difference in miscarriage rate; however oocyte yield was lower in the DHEA-treated group compared with controls. Given the small sample size, any conclusions of this meta-analysis should be cautiously interpreted. Two meta-analyses examined the use of androgens and androgen-modulating agents on IVF outcome for poor responders. These came to discordant conclusions. Sunkara et al. [109] included nine studies, of which five were randomized controlled studies. Two studies were of transdermal testosterone [76, 77], two of DHEA [84, 86], and the remaining of aromatase inhibitor [27, 101, 102, 104, 105]. Clinical pregnancy rate was not significantly increased in the treated women in the meta-analysis of RCT and of non-RCT studies. There was also no significant increase in clinical pregnancy in women treated with aromatase inhibitor. Analysis of the four studies using testosterone and DHEA showed significantly increased clinical pregnancy rate. Total gonadotropin dosage was significantly lower in androgen-treated women compared with controls, but length of treatment was not different. There was no difference detected in cycle cancellation rates, oocytes retrieved, or ongoing pregnancy rate. Sunkara concluded that there was insufficient evidence to support androgen use for poor responders.
Bosdou [110] published a meta-analysis in 2012. This analysis included 13 RCTs reporting use of aromatase inhibitors [105, 111], DHEA [86], transdermal testosterone [76, 79], recombinant LH [112–118], and recombinant hCG [115]. Analysis of the studies reporting transdermal testosterone revealed significantly increased oocytes retrieved, clinical pregnancy and live birth rates, lower GT dose, and shorter duration of GT (gonadotropin) stimulation. In contrast, the single DHEA study analyzed showed no difference in number of oocytes retrieved, clinical pregnancy, or live birth rates. Clinical pregnancy was not shown to be significantly different in the meta-analysis of studies reporting treatment with aromatase inhibitor; live birth rates were not reported. Total gonadotropin dose was significantly reduced with aromatase inhibitor, while oocyte yield showed no difference. All forms of androgens and androgen-modulating agents presented in the meta-analysis demonstrated a trend toward increased clinical pregnancy rate; however there was lack of scientific evidence to confirm these findings.
The results of the meta-analyses do not provide consistent conclusions; however, all analyses showed higher clinical pregnancy rates with transdermal testosterone. Analysis of DHEA supplementation, aromatase inhibitor, rLH, and RhCG were not able to show clear advantage to enable clinical recommendation of androgens or androgen-modulating agents for poor responders.
15.5 Potential Adverse Effects of Androgens
Androgens have the potential for various adverse effects including oily skin, acne vulgaris, deep voice, hair loss, and other masculinizing features. There is one report of a patient who presented with posttraumatic seizure after 1 month of DHEA supplementation [119]. Gleicher et al. reported no adverse effects in over 1,000 women treated with DHEA [56]. Wiser also showed no adverse effects of androgens [86]. Massin and Kim concluded that there are no adverse effects in women treated with transdermal testosterone and no evidence of congenital malformations [76, 79]. Aromatase inhibitors were thought to be associated with congenital malformations [120], but a subsequent study of five Canadian centers demonstrated that there was very low risk of congenital malformations or chromosomal abnormalities [121]. In women treated with long-term aromatase inhibitors for breast cancer, carpal tunnel syndrome and musculoskeletal events have been reported [122, 123].
It is prudent to note that testosterone is used for continuing replacement therapy in both men and women, as well as in transsexuals. In female-male transsexuals treated with testosterone, incidence of cardiovascular disease and myocardial infarction was comparable to rates in women [124]. DHEA is also used in postmenopausal women long term. It has been shown to be beneficial in terms of bone density [125, 126] with possible benefits for memory, cognitive function, and libido. A study of women treated with 1 year of DHEA showed no adverse effects in terms of either lipid or insulin profiles [127].
15.6 Clinical Applications and Recommendations
Recent evidence suggests that the problem in poor responders is not low intraovarian androgens in the actual phase of oocyte retrieval, but rather long-term deficiency, which impacts on the ovarian microenvironment [56, 62]. It appears logical that androgen therapy should be used as priming rather than adjuvant therapy during the treatment cycle. The process of folliculogenesis, reaching the antral stage where the follicle would express androgen receptor, takes weeks, and it is unclear how long treatment with exogenous androgens would be required in order to improve the functional ovarian reserve [128]. DHEA synthesis in the theca cells occurs approximately 70 days prior to ovulation, so supplementation for at least 3–4 months seems logical [57]. Long-term androgen priming seems to be necessary to increase recruitment of small antral follicles [84, 88]. Long-term aromatase inhibitor therapy, as suggested by Feigenberg [24], may also potentially improve the cohort of early follicles.
DHEA can be offered to patients waiting for their next IVF cycle, which can often be motivating as women feel that they are doing something practical to improve their chances of success. DHEA appears to be dispensed widely among poor responders, while transdermal testosterone seems to be less popular, despite the stronger scientific evidence for transdermal testosterone in terms of clinical pregnancy and live birth outcomes. Like the initial patient reported by Barad who self-medicated with DHEA [82], many poor responders are purchasing DHEA of their own volition, not necessarily in conjunction with their treatment plan. Retrospective and case control studies seem to point toward a benefit for androgen therapy in poor responders, even if level 1 evidence is still lacking.
Aromatase inhibitors, while not strictly androgens, work by increasing endogenous androgens. Although these also have not been proven for poor responders, they are being increasingly used in minimal stimulation protocols for poor responders. The benefit of aromatase inhibitors for ovulation induction and as an adjunct to gonadotropin stimulation for IVF in fertility preservation therapy is obvious.
15.7 Future Research
Much of the research to date regarding androgen use in controlled ovarian stimulation, including the meta-analyses presented in this chapter, appears to be confounding and vague. This is in part due to lack of uniform definition of poor responders, as well as wide variation in treatment protocols. Further RCTs with clear definition of patient cohorts, as well as standardized adjuvant androgen therapy protocol, will hopefully provide more distinct evidence to either support or invalidate use of androgens for poor responders.
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