Paolo Giovanni Artini1 , Giovanna Simi1, Maria Elena Rosa Obino1, Sara Pinelli1, Olga Maria Di Berardino1, Francesca Papini1, Maria Ruggiero1 and Vito Cela1
(1)
Division of Obstetrics and Gynecology, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
Paolo Giovanni Artini
Email: paolo.artini@med.unipi.it
Keywords
DHEA supplementationPoor respondersIVFOvarian reserve
13.1 Introduction
Poor response to ovarian stimulation (POR) usually indicates a reduction in follicular response to ovarian stimulation during in vitro fertilization (IVF) cycles resulting in a reduced number of retrieved oocytes. In recent years, mainly due to the postponement of childbearing and the consequent decrease of ovarian reserve, often a POR occurs during IVF despite the high dose of gonadotropins administered. Incidence of POR has been reported from 9 to 24 % [1, 2], and even if this condition may occur unexpectedly, its prevalence increases with age, and it is >50 % in patients over 40 years [3]. Patients with POR are defined as poor responders.
In March 2010, the European Society of Human Reproduction and Embryology (ESHRE) established the criteria for POR diagnosis. Until that, in fact, there was not a uniform definition and the term POR indicated heterogeneous groups of patients. The ESHRE established that at least two of the following three features must be present, in order to diagnose POR:
1.
2.
3.
Two episodes of POR after maximal stimulation are sufficient to define a patient as a “poor responder” without advanced maternal age or abnormal ORT. In the case of women over 40 years with an abnormal ORT, we are allowed to talk about “expected POR” [3].
Poor responders remain a challenging group of patients to manage in an IVF program. Despite that in literature there are several publications about poor ovarian response, there is not enough evidence to support the use of any particular protocol in poor responder patients.
13.2 Ovarian Reserve Assessment for Fertility Management
Age and day 3 levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) have been used as indicators of ovarian response to ART for several years. The basal FSH concentration is the most common test used for ovarian screening [4]. However, it has been reported that the increase in FSH levels occurs late in the sequence of events associated with ovarian aging [5]; hence, this increase may be of limited clinical use as a marker [6].
Several studies reported the efficiency of antral follicle count (AFC) and ovarian volume in predicting ovarian response to ovarian stimulation [7]. Ovarian antral follicles larger than 2 mm are extremely sensitive and responsive to FSH and are defined as “recruitable.” They can be visualized and measured with transvaginal ultrasound, and the total number of 2–10 mm follicles in both the ovaries represents the AFC [8, 9].
A new endocrine marker, anti-Müllerian hormone (AMH), was evaluated by several study groups as a marker of ovarian response. In women, AMH is produced in the ovary by the granulosa cells surrounding preantral and small antral follicles [10, 11]. AMH expression in ovaries has been observed as early as 36 weeks of gestation in humans [12], is barely detectable in the serum at birth, and increases after puberty [12, 13]. AMH expression declines with advancing female age, to become undetectable again at the time of the menopause [14]. The correlation between AMH levels and the number of antral follicles measured by ultrasound is well established [15–17]. Therefore, AMH levels are believed to be the best representation of the gradual decline in reproductive capacity in women [18, 19], and AMH has been shown to be an accurate marker for the occurrence of poor response to ovarian hyperstimulation with gonadotropins in IVF [16, 20–22]. AMH and AFC are nowadays considered two markers with similar diagnostic performance [23, 24].
13.3 Management of Infertility
Management of poor responder patients is challenging for fertility experts. Women with POR retrieve less oocytes and have less embryos for transfer, and their chances of pregnancy are obviously lower. Frequently, their cycles have to be cancelled because of the absence of follicular development, the lack of oocytes retrieved, or the failure to develop embryos [1, 3, 25, 26]. Poor responder patients can be treated in various ways, either by trying stimulation protocols using high doses of gonadotropins associated with different dosages and timing of GnRH analogs or antagonists or by trying IVF in a natural cycle or with minimal stimulation. Several studies finally suggested the supplementation with hormones like growth hormone, estradiol, androgens, and dehydroepiandrosterone.
13.4 Physiology of DHEA
Dehydroepiandrosterone (DHEA) is a weak androgen produced by the conversion of cholesterol by the adrenal cortex, the central nervous system, and the ovarian theca cells and is converted mainly in peripheral tissue to more active forms of androgen or estrogen [27]. DHEA is abundant during female reproductive life and progressively declines by approximately 2 % per year [28]. This has led some authors to hypothesize that DHEA supplementation may slow down the aging process [29]. Even after 70 years of research, the physiology of DHEA is not fully understood.
DHEA beneficial effects increase over time, and best results are obtained after 4–5 months of supplementation with 75 mg of micronized DHEA daily, a time period similar to the complete follicular recruitment cycle [30]. Numerous hypotheses have been made on how DHEA promotes fertility. Besides serving as an essential prohormone in ovarian follicular steroidogenesis, facilitating follicular function and growth [31, 32], DHEA seems to increase follicular insulin-like growth factor-I (IGF-I) concentrations by ≅150 %, probably independent of changes in GH secretion [33, 34]. This may indicate that DHEA stimulates hepatic and end-organ IGF-1 response to GH, which can promote the gonadotropin effect. In animal models, DHEA has also shown to promote a polycystic environment in the ovaries, with promotion of antral follicle growth, increased levels of active oocytes, and decreased atretic effects [33, 35–37]. Androgens, long considered antagonist of normal follicle recruitment and development, thus assume a crucial role in female fertility: some reports demonstrated that androgens act on folliculogenesis by increasing the number of FSH receptors expressed in the granulosa cells [38]. On the other hand, the addition of androgens in COH is thought to have a positive role in follicular recruitment and granulosa cell proliferation [39]. Moreover, studies have shown the beneficial effect of DHEA administration on vascular function. In fact, DHEA increases vascular endothelial proliferation, migration, and vascular tube formation. DHEA also promotes nitric oxide synthesis, at physiological levels, in intact vascular endothelial cells, inducing vasodilatation [40]. This effect can be very important for vascular function also in the female reproductive system, considering that ovarian folliculogenesis is accompanied by a very finely regulated angiogenesis.
VEGF (vascular endothelial growth factor) is a molecule produced by follicular granulose and ovarian thecal cells in response to gonadotropin stimulation [41]. Indeed, VEGF is implied in endothelial sprouting, enhanced vascular permeability, expression of tissue matrix metalloproteinases and finally in the digestion of matrix, required for the endothelial cells to move [42]. Among its function, VEGF has the role of primary mediator for the formation of a vascular network in the thecal cell layer of the follicle [42, 43].
Van Blerkom et al. [44] observed higher VEGF levels in follicles with higher dissolved oxygen contents and with increased blood flow observed at Doppler, but they failed to find a specific association between follicular VEGF levels and the presumed extent of perifollicular vascularization. A similar conclusion was obtained by Barroso et al. and Battaglia et al., even if FF (follicular fluids) levels of VEGF in poor responder patients were found higher than in normo-responders [45, 46]. Besides, Kan and associates more recently did not show any difference in FF VEGF concentrations among poor responders with and without high-grade perifollicular vascularity [47].
As a consequence, other angiogenic factors might be involved in the process of cellular reaction to hypoxia, acting synergistically or additionally with VEGF, and actually follicular oxygen content seems not to be predictable only by US. Transcriptional upregulation of VEGF is stimulated by HIF1 (hypoxic-inducible factor 1), during cellular adaptation to hypoxia. HIF1 is a transcription factor sensible to low oxygen tension, which prevents fatal depletion of oxygen and subsequent cell death. As a consequence, FF concentrations of this factor are linked by an inverse correlation with the available oxygen, being involved in a certain way in the determination of oocyte developmental competence.
13.5 Therapy with DHEA
Casson and associates, in 2000, firstly suggested an improvement of ovarian function in patients with reduced ovarian reserve from supplementation with DHEA [48]. In their study, they presented young women with unexplained infertility and FSH levels <20 mIU/ml treated with a dose of 80 mg of DHEA daily for 2 months. They did not observe any significant improvements of pregnancy rates, but E2 levels were tripled in all women, and the number of follicles retrieved was doubled. Few years later, Barad and Gleicher published a case-control study in which 25 women were evaluated in their respective IVF cycle outcomes pre- and posttreatment with DHEA, with the same ovarian protocol stimulation [30]. The supplementation was well tolerated by all patients, demonstrating higher number of fertilized oocytes, transferred embryos, and embryo score per oocyte, besides improved oocytes and embryo quality.
In 2007, Barad and Gleicher published a case-control study on 190 women aged more than 30 with poor ovarian response, treated with the same stimulation protocol [37]. Study group used supplementation with 25 mg DHEA three times daily for up to 4 months, while the control group underwent infertility treatment but without DHEA. In the DHEA group, they observed a lower cancellation rate, even if not statistically significant, and a better clinical pregnancy rate (PR), in respect to the control group, despite prognostically more favorable controls and higher mean age in the DHEA group. The miscarriage rate per clinical pregnancy was also found lower in the study group, but these data were not statistically significant.
In 2007 in a small pilot study, the same authors presented 8 patients with premature ovarian aging (POA), who received DHEA for at least 1 month (study group), and 19 women with POA who were not treated with DHEA (control group). The study group demonstrated that DHEA may reduce aneuploidy, but unfortunately, the small number of patients in the study awarded to it an insufficient statistical power [49].
This result was confirmed by the study of the same authors published in 2010, where they concluded that the beneficial effects of DHEA supplementation on miscarriage rates were, at least partially, the likely consequence of lower embryo aneuploidy [50].
An interesting study conducted by Gleicher and collaborators in 2009 reported a significantly decreased miscarriage rate after DHEA supplementation, as opposed to total miscarriage rate in the national US registry, that was attributed by the authors to diminished aneuploid embryo rates, as aneuploidy is a consequence of ovarian aging [51].
A study by Mamas and Mamas, in 2009 [31], presented really interesting results: five premature ovarian failure (POF) patients conceived after at least 2 months of DHEA supplementation, which led to regular periods and decreased serum FSH concentrations and increased serum estradiol concentrations.
In the same year, Sonmezer and associates compared the result of a second cycle of 19 patients treated with DHEA 25 mg t.i.d. with the parameters of the previous, failed, cycle of stimulation. They noted a statistically significant improvement in the number of follicles >17 mm recruited, oocytes retrieved, and MII oocytes and a better quality of embryos. Furthermore, there was a statistically significant improvement in pregnancy rate per patient and per transferred embryo, clinical pregnancies, and implantation rate.
Wiser and associates most recently published the first randomized, prospective, controlled study of supplementation with 75 mg of DHEA orally once a day, at least 6 weeks before starting the first IVF cycle. DHEA patients showed significantly higher live birth rates [52].
In our study [53], published in 2012, we analyzed the effect of DHEA supplementation on follicular microenvironment and on in vitro fertilization (IVF) outcomes among 24 poor responder patients. One group received 25 mg/die of DHEA three times daily for 3 months previous to IVF cycle, while the other group did not receive any treatment. In both groups, we evaluated perifollicular vascularization of recruited follicles through power Doppler blood flow analysis, and follicles were graded as described by Chui et al., according to the percentage of follicular circumference in which most flow was identified from a single cross-sectional slice [54]. The grading system was as follows: <25 % follicular circumference in which blood flow was identified (F1), 26–50 % (F2), 51–75 % (F3), and 76–100 % (F4). Follicular fluids (FF) from F3 to F4 follicles were collected, and FF levels of vascular endothelial growth factor (VEGF) and hypoxic-inducible factor 1 (HIF1) were measured. Results showed that FF levels of HIF1 were statistically significantly lower in women treated with DHEA (14.76 ± 51.13 vs. 270.03 ± 262.18 pg/ml; p = 0.002). On the contrary, VEGF levels did not differ between the two groups. Concerning COH, in the DHEA group, the mean duration of treatment was significantly shorter (9.83 ± 1.85 vs. 12.09 ± 2.81; p = 0.023). Total numbers of oocytes retrieved, fertilized oocytes, good-quality embryos, transferred embryos, and clinical pregnancies tended to be higher in study group, but the results were not significant. On the other hand, considering the oocytes retrieved in selected F3–F4 follicles, there was a relation between HIF1 levels and oocyte quality. In fact, mature oocytes retrieved in selected follicles were significantly more numerous in the DHEA group (0.50 ± 0.52 vs. 0.08 ± 0.29; p = 0.018). Therefore, our data show that DHEA supplementation in poor responder patients can improve the perifollicular vascularization, enhancing oxygen levels in follicular fluid, which is important in order to develop oocytes and embryo of good quality. Thus, the improvement of reproductive parameters after DHEA supplementation in poor responder patients could be explained through the effect that this prohormone has on follicular microenvironment.
Recently, Fusi and associates described unexpected spontaneous pregnancies in poor responder patients with long-term infertility, treated with DHEA supplementation prior to IVF. They analyzed two groups of women. The first group included 39 young women with <40 years all treated with DHEA because of a previous poor response. The second group included 38 women over 40 years who received DHEA supplementation. Controls for the latter group were 24 comparable women who had not been treated with DHEA before the first IVF cycle to evaluate the spontaneous pregnancy rate during preparation to IVF. Three tablets daily of 25 mg micronized DHEA were administered for at least 12 weeks before starting a long stimulation protocol for IVF. Surprisingly, they observed 10 spontaneous pregnancies and 9 spontaneous ongoing pregnancies among young poor responders. Pregnancy rate and ongoing pregnancy rate obtained before starting the IVF cycle were also significantly higher in older women treated with DHEA than in the control group: 21.05 and 13.15 and 4.1 % and 0, respectively [55].
13.6 Conclusions
In conclusion, despite the need of more strong data from good-quality randomized controlled trials (RCTs) with relevant outcomes and follow-up [26], it seems clear that DHEA represents a promising option for the treatment of a large number of women who are really challenging for IVF specialists. In addition to the possible benefits in terms of increase of reproductive parameters, DHEA offers the possibility to choose a milder and more cost-effective hormonal protocol. Without supplementation with DHEA, specialists would be forced to use heavy hormonal doses, with minimal response or, as the last resort, egg donation [56].
References
1.
Kyrou D, Kolibianakis EM, Venetis CA, Papanikolaou EG, Bontis J, Tarlatzis BC (2009) How to improve the probability of pregnancy in poor responders undergoing in vitro fertilization: a systematic review and meta-analysis. Fertil Steril 91:749–766PubMedCrossRef
2.
Fasouliotis SJ, Simon A, Laufer N (2000) Evaluation and treatment of low responders in assisted reproductive technology: a challenge to meet. J Assist Reprod Genet 17:357–373PubMedCentralPubMedCrossRef
3.
Ferraretti AP, La Marca A, Fauser BCJM, Tarlatzis B, Nargund G, Gianaroli L (2011) ESHRE consensus on the definition of “poor response” to ovarian stimulation for in vitro fertilization: the Bologna criteria. Hum Reprod 26:1616–1624PubMedCrossRef
4.
Loverro G, Nappi L, Mei L, Giacomoantonio L, Carriero C, Tartagni M (2003) Evaluation of functional ovarian reserve in 60 patients. Reprod Biomed Online 7:200–204PubMedCrossRef
5.
Klein NA, Battaglia DE, Fujimoto VY, Davis GS, Bremner WJ, Soules MR (1996) Reproductive aging: accelerated ovarian follicular development associated with a monotropic follicle-stimulating hormone rise in normal older women. J Clin Endocrinol Metab 81:1038–1045PubMed
6.
Bancsi LF, Huijs AM, den Ouden CT, Broekmans FJ, Looman CW, Blankenstein MA et al (2000) Basal follicle-stimulating hormone levels are of limited value in predicting ongoing pregnancy rates after in vitro fertilization. Fertil Steril 73:552–557PubMedCrossRef
7.
Bancsi LFJMM, Broekmans FJM, Eijkemans MJC, de Jong FH, Habbema JDF, te Velde ER (2002) Predictors of poor ovarian response in in vitro fertilization: a prospective study comparing basal markers of ovarian reserve. Fertil Steril 77:328–336PubMedCrossRef
8.
Broekmans FJM, de Ziegler D, Howles CM, Gougeon A, Trew G, Olivennes F (2010) The antral follicle count: practical recommendations for better standardization. Fertil Steril 94:1044–1051PubMedCrossRef
9.
La Marca A, Spada E, Sighinolfi G, Argento C, Tirelli A, Giulini S et al (2011) Age-specific nomogram for the decline in antral follicle count throughout the reproductive period. Fertil Steril 95:684–688PubMedCrossRef
10.
Durlinger ALL, Visser JA, Themmen APN (2002) Regulation of ovarian function: the role of anti-Müllerian hormone. Reproduction 124:601–609PubMedCrossRef
11.
Weenen C, Laven JSE, Von Bergh ARM, Cranfield M, Groome NP, Visser JA et al (2004) Anti-Müllerian hormone expression pattern in the human ovary: potential implications for initial and cyclic follicle recruitment. Mol Hum Reprod 10:77–83PubMedCrossRef
12.
Rajpert-De Meyts E, Jørgensen N, Graem N, Müller J, Cate RL, Skakkebaek NE (1999) Expression of anti-Müllerian hormone during normal and pathological gonadal development: association with differentiation of Sertoli and granulosa cells. J Clin Endocrinol Metab 84:3836–3844PubMed
13.
Guibourdenche J, Lucidarme N, Chevenne D, Rigal O, Nicolas M, Luton D et al (2003) Anti-Müllerian hormone levels in serum from human foetuses and children: pattern and clinical interest. Mol Cell Endocrinol 211:55–63PubMedCrossRef
14.
La Marca A, De Leo V, Giulini S, Orvieto R, Malmusi S, Giannella L et al (2005) Anti-Mullerian hormone in premenopausal women and after spontaneous or surgically induced menopause. J Soc Gynecol Investig 12:545–548PubMedCrossRef
15.
De Vet A, Laven JSE, de Jong FH, Themmen APN, Fauser BCJM (2002) Antimüllerian hormone serum levels: a putative marker for ovarian aging. Fertil Steril 77:357–362PubMedCrossRef
16.
Van Rooij IAJ, Broekmans FJM, te Velde ER, Fauser BCJM, Bancsi LFJMM, de Jong FH et al (2002) Serum anti-Müllerian hormone levels: a novel measure of ovarian reserve. Hum Reprod 17:3065–3071PubMedCrossRef
17.
Fanchin R, Schonäuer LM, Righini C, Guibourdenche J, Frydman R, Taieb J (2003) Serum anti-Müllerian hormone is more strongly related to ovarian follicular status than serum inhibin B, estradiol, FSH and LH on day 3. Hum Reprod 18:323–327PubMedCrossRef
18.
Van Rooij IAJ, den Tonkelaar I, Broekmans FJM, Looman CWN, Scheffer GJ, de Jong FH et al (2004) Anti-müllerian hormone is a promising predictor for the occurrence of the menopausal transition. Menopause 11:601–606PubMedCrossRef
19.
Van Rooij IAJ, Broekmans FJM, Scheffer GJ, Looman CWN, Habbema JDF, de Jong FH et al (2005) Serum antimullerian hormone levels best reflect the reproductive decline with age in normal women with proven fertility: a longitudinal study. Fertil Steril 83:979–987PubMedCrossRef
20.
Hazout A, Bouchard P, Seifer DB, Aussage P, Junca AM, Cohen-Bacrie P (2004) Serum antimüllerian hormone/müllerian-inhibiting substance appears to be a more discriminatory marker of assisted reproductive technology outcome than follicle-stimulating hormone, inhibin B, or estradiol. Fertil Steril 82:1323–1329PubMedCrossRef
21.
Fanchin R, Méndez Lozano DH, Louafi N, Achour-Frydman N, Frydman R, Taieb J (2005) Dynamics of serum anti-Müllerian hormone levels during the luteal phase of controlled ovarian hyperstimulation. Hum Reprod 20:747–751PubMedCrossRef
22.
Satwik R, Kochhar M, Gupta SM, Majumdar A (2012) Anti-mullerian hormone cut-off values for predicting poor ovarian response to exogenous ovarian stimulation in in-vitro fertilization. J Hum Reprod Sci 5:206–212PubMedCentralPubMedCrossRef
23.
La Marca A, Sighinolfi G, Radi D, Argento C, Baraldi E, Artenisio AC et al (2010) Anti-Mullerian hormone (AMH) as a predictive marker in assisted reproductive technology (ART). Hum Reprod Update 16:113–130PubMedCrossRef
24.
Broer SL, Dólleman M, Opmeer BC, Fauser BC, Mol BW, Broekmans FJM (2011) AMH and AFC as predictors of excessive response in controlled ovarian hyperstimulation: a meta-analysis. Hum Reprod Update 17:46–54PubMedCrossRef
25.
Loutradis D, Vomvolaki E, Drakakis P (2008) Poor responder protocols for in-vitro fertilization: options and results. Curr Opin Obstet Gynecol 20:374–378PubMedCrossRef
26.
Pandian Z, McTavish AR, Aucott L, Hamilton MP, Bhattacharya S (2010) Interventions for “poor responders” to controlled ovarian hyper stimulation (COH) in in-vitro fertilisation (IVF). Cochrane Database Syst Rev (1):CD004379
27.
Burger HG (2002) Androgen production in women. Fertil Steril 77(Suppl 4):S3–S5PubMedCrossRef
28.
Walker ML, Anderson DC, Herndon JG, Walker LC (2009) Ovarian aging in squirrel monkeys (Saimiri sciureus). Reproduction 138:793–799PubMedCrossRef
29.
Casson PR, Carson SA, Buster JE (1998) Testosterone delivery systems for women: present status and future promise. Semin Reprod Endocrinol 16:153–159PubMedCrossRef
30.
Barad D, Gleicher N (2006) Effect of dehydroepiandrosterone on oocyte and embryo yields, embryo grade and cell number in IVF. Hum Reprod 21:2845–2849PubMedCrossRef
31.
Mamas L, Mamas E (2009) Premature ovarian failure and dehydroepiandrosterone. Fertil Steril 91:644–646PubMedCrossRef
32.
Hillier SG, Whitelaw PF, Smyth CD (1994) Follicular oestrogen synthesis: the “two-cell, two-gonadotrophin” model revisited. Mol Cell Endocrinol 100:51–54PubMedCrossRef
33.
Casson PR, Santoro N, Elkind-Hirsch K, Carson SA, Hornsby PJ, Abraham G et al (1998) Postmenopausal dehydroepiandrosterone administration increases free insulin-like growth factor-I and decreases high-density lipoprotein: a six-month trial. Fertil Steril 70:107–110PubMedCrossRef
34.
Morales AJ, Nolan JJ, Nelson JC, Yen SS (1994) Effects of replacement dose of dehydroepiandrosterone in men and women of advancing age. J Clin Endocrinol Metab 78:1360–1367PubMed
35.
Orvieto R, Bar-Hava I, Yoeli R, Ashkenazi J, Rabinerson D, Bar J et al (2004) Results of in vitro fertilization cycles in women aged 43–45 years. Gynecol Endocrinol 18:75–78PubMedCrossRef
36.
Vendola K, Zhou J, Wang J, Famuyiwa OA, Bievre M, Bondy CA (1999) Androgens promote oocyte insulin-like growth factor I expression and initiation of follicle development in the primate ovary. Biol Reprod 61:353–357PubMedCrossRef
37.
Barad D, Brill H, Gleicher N (2007) Update on the use of dehydroepiandrosterone supplementation among women with diminished ovarian function. J Assist Reprod Genet 24:629–634PubMedCentralPubMedCrossRef
38.
Weil S, Vendola K, Zhou J, Bondy CA (1999) Androgen and follicle-stimulating hormone interactions in primate ovarian follicle development. J Clin Endocrinol Metab 84:2951–2956PubMedCrossRef
39.
Feigenberg T, Simon A, Ben-Meir A, Gielchinsky Y, Laufer N (2009) Role of androgens in the treatment of patients with low ovarian response. Reprod Biomed Online 19:888–898PubMedCrossRef
40.
Liu D, Iruthayanathan M, Homan LL, Wang Y, Yang L, Wang Y et al (2008) Dehydroepiandrosterone stimulates endothelial proliferation and angiogenesis through extracellular signal-regulated kinase 1/2-mediated mechanisms. Endocrinology 149:889–898PubMedCentralPubMedCrossRef
41.
Kamat BR, Brown LF, Manseau EJ, Senger DR, Dvorak HF (1995) Expression of vascular permeability factor/vascular endothelial growth factor by human granulosa and theca lutein cells. Role in corpus luteum development. Am J Pathol 146:157–165PubMedCentralPubMed
42.
Ferrara N (2004) Vascular endothelial growth factor: basic science and clinical progress. Endocr Rev 25:581–611PubMedCrossRef
43.
Lam PM, Haines C (2005) Vascular endothelial growth factor plays more than an angiogenic role in the female reproductive system. Fertil Steril 84:1775–1778PubMedCrossRef
44.
Van Blerkom J, Antczak M, Schrader R (1997) The developmental potential of the human oocyte is related to the dissolved oxygen content of follicular fluid: association with vascular endothelial growth factor levels and perifollicular blood flow characteristics. Hum Reprod 12:1047–1055PubMedCrossRef
45.
Barroso G, Barrionuevo M, Rao P, Graham L, Danforth D, Huey S et al (1999) Vascular endothelial growth factor, nitric oxide, and leptin follicular fluid levels correlate negatively with embryo quality in IVF patients. Fertil Steril 72:1024–1026PubMedCrossRef
46.
Battaglia C, Genazzani AD, Regnani G, Primavera MR, Petraglia F, Volpe A (2000) Perifollicular Doppler flow and follicular fluid vascular endothelial growth factor concentrations in poor responders. Fertil Steril 74:809–812PubMedCrossRef
47.
Kan A, Ng EHY, Yeung WSB, Ho PC (2006) Perifollicular vascularity in poor ovarian responders during IVF. Hum Reprod 21:1539–1544PubMedCrossRef
48.
Casson PR, Lindsay MS, Pisarska MD, Carson SA, Buster JE (2000) Dehydroepiandrosterone supplementation augments ovarian stimulation in poor responders: a case series. Hum Reprod 15:2129–2132PubMedCrossRef
49.
Gleicher N, Weghofer A, Barad D (2007) Increased euploid embryos after supplementation with dehydroepiandrosterone (DHEA) in women with premature ovarian aging. Fertil Steril 88, Supplement 1:S232CrossRef
50.
Gleicher N, Weghofer A, Barad DH (2010) Dehydroepiandrosterone (DHEA) reduces embryo aneuploidy: direct evidence from preimplantation genetic screening (PGS). Reprod Biol Endocrinol 8:140PubMedCentralPubMedCrossRef
51.
Gleicher N, Ryan E, Weghofer A, Blanco-Mejia S, Barad DH (2009) Miscarriage rates after dehydroepiandrosterone (DHEA) supplementation in women with diminished ovarian reserve: a case control study. Reprod Biol Endocrinol 7:108PubMedCentralPubMedCrossRef
52.
Wiser A, Gonen O, Ghetler Y, Shavit T, Berkovitz A, Shulman A (2010) Addition of dehydroepiandrosterone (DHEA) for poor-responder patients before and during IVF treatment improves the pregnancy rate: a randomized prospective study. Hum Reprod 25:2496–2500PubMedCrossRef
53.
Artini PG, Simi G, Ruggiero M, Pinelli S, Di Berardino OM, Papini F et al (2012) DHEA supplementation improves follicular microenvironment in poor responder patients. Gynecol Endocrinol 28:669–673PubMedCrossRef
54.
Chui DK, Pugh ND, Walker SM, Gregory L, Shaw RW (1997) Follicular vascularity–the predictive value of transvaginal power Doppler ultrasonography in an in-vitro fertilization programme: a preliminary study. Hum Reprod 12:191–196PubMedCrossRef
55.
Fusi FM, Ferrario M, Bosisio C, Arnoldi M, Zanga L (2013) DHEA supplementation positively affects spontaneous pregnancies in women with diminished ovarian function. Gynecol Endocrinol 29:940–943PubMedCrossRef
56.
Mamas L, Mamas E (2009) Dehydroepiandrosterone supplementation in assisted reproduction: rationale and results. Curr Opin Obstet Gynecol 21:306–308PubMedCrossRef