PCOS is a complex and heterogeneous syndrome. Women with PCOS who have HA are often treated with OC, while those with obesity, especially with insulin resistance, may gain particular benefits from metformin therapy . Treatment with OC and metformin can reduce androgen levels and improve insulin sensitivity; however, the influence of these treatments on serum AMH concentrations remains debated.
In the present study, we treated patients with OC and metformin according to their different endocrine and metabolic disturbances, following routine therapies used in clinical practice. It is difficult to conduct randomized controlled trials on the effects of different treatments on AMH in patients with PCOS, as PCOS women have heterogeneous manifestations. Thus far, there are few randomized controlled trials with large samples in this field. AMH values were compared before and after treatment within each group in this study. Importantly, self-controlled trials avoid the influence of individual differences on outcomes. Our results are reliable and have clinical implications for PCOS patients regarding these treatments. Although HA is the major feature and diagnostic component of PCOS, the clinical signs of HA might vary with ethnic differences. The rate of HA is lower in Chinese women with PCOS than in Western women. We herein selected biochemical HA as the criterion for treatment of PCOS, regardless of the symptoms of HA.
Androgens increase the recruitment of follicles but inhibit the selection of the dominant follicle , and therefore women with PCOS exhibit excessive numbers of preantral and small antral follicles . This excessive number of small antral follicles induced by androgens and the increase in AMH production per granulosa cell result in elevated serum AMH concentrations in PCOS patients [4, 23]. In addition, high levels of LH stimulate excessive secretion of androgen in polycystic ovaries. Bungum et al.  observed a significant positive co-variation between LH and AMH, and this phenomenon suggested that LH was a possible factor involved in the control of AMH secretion. Consequently, AMH was positively correlated with testosterone and LH levels as well as total numbers of follicles [8, 9], and serum AMH levels significantly increased with HA [8, 11, 26].
OC can inhibit LH release and reduce androgen levels. However, it remains debatable whether AMH levels decline during therapy with OC. Fábregues et al.  reported that AMH levels significantly decreased during OC treatment, explaining that the reduction in androgens and LH during OC therapy contributed to the significant decrease in serum AMH. Similar results were reported by Panidis et al. , who showed a significant diminution in serum AMH in women with PCOS after 6 months of treatment with OC (2 mg of cyproterone acetate plus 35 µg of ethinyl E2). In our study, AMH concentrations significantly decreased after 3 months of OC therapy, with the reduction in AMH being a consequence of the suppression by OC of serum LH and testosterone levels. Our data are therefore in accordance with previous studies [11, 16]. By contrast, Somunkiran et al.  did not find significant changes in AMH levels after 6 months of contraceptive treatment in women with PCOS. Our study is not consistent with that of Somunkiran et al. , as they did not observe a correlation between AMH levels and LH, FSH, or testosterone.
Birch et al.  reported that after adjusting for age, AMH was 19% lower in OC users compared with non-users. However, the inhibitory effect of OC on AMH may be reversed within 3–6 months . Based on our data and the previously aforementioned studies [11, 16], elevated AMH levels decreased significantly during OC treatment, suggesting that AMH is a useful indicator to evaluate OC treatment efficacy in clinical practice. In the current study, BMI, serum insulin levels, and HOMA-IR were not negatively affected by OC use.
Concomitant metabolic disorders constitute another prominent feature of PCOS, including obesity, IR, and metabolic syndrome . IR and hyperinsulinemia are known as important pathogenic factors for PCOS, although they are not included in the definition . AMH levels were found to be positively correlated with insulin and HOMA-IR in several studies [9, 10], suggesting that insulin plays a role in AMH synthesis and secretion . Investigators have reported controversial results regarding the influence of metformin on AMH levels in PCOS patients. Two studies showed that after treatment with metformin, AMH concentrations were significantly reduced [5, 29]; however, in a study by Nascimento et al. , patients with IR received metformin for 8 weeks, and although serum insulin concentrations and androgen levels decreased, AMH levels did not change significantly. Nascimento et al.  speculated that the effect of metformin on AMH levels was associated with dosage and duration of treatment. Fleming et al.  found that the reduction in AMH levels due to metformin provided a delayed response because elevated serum AMH levels did not change until the second 4-month period. Two other reports showed that metformin treatment significantly decreased AMH levels in hyperinsulinemic patients [31, 32].
In summary, several studies have suggested that the reduction in AMH levels after metformin treatment is primarily observed in highly insulin-resistant patients with PCOS [31, 32], and that the influence on peripheral serum AMH concentrations is most likely related to the dose of metformin and the duration of treatment [20, 30]. In the present study, even though metformin treatment significantly reduced BMI, serum insulin concentrations, and HOMA-IR, AMH levels remained unaffected. Contrary to the research by Romualdi et al. . and Grigoryan et al. , we found that metformin treatment failed to decrease circulating AMH levels in PCOS patients with IR. In the present study, although BMI, serum insulin levels, and HOMA-IR were decreased significantly after treatment, the values for these parameters were still abnormal. Serum AMH levels dropped from 10.33 ± 4.34 ng/mL to 10.13 ± 4.14 ng/mL, suggesting a decreasing tendency after metformin treatment. Perhaps a higher dose or a longer duration of metformin treatment is needed to observe clear effects on AMH levels. Thus, the influence of metformin treatment on circulating AMH concentrations in PCOS women requires further study, especially with a larger sample size, in order to reach definitive conclusions.
Combined OC and metformin treatment is superior to OC alone in improving IR and is more effective in decreasing androgen levels than metformin monotherapy . In clinical practice, combined treatment is more effective for those patients with obesity or IR and HA or elevated serum LH levels. However, very few data are available on the impact of the combination of OC and metformin therapy on AMH levels in women with PCOS. A recent study revealed that AMH levels significantly decreased in a cohort of adolescents with PCOS after treatment with metformin plus OC . In our study, combined treatment resulted in a significant decrease in BMI, fasting insulin levels, and HOMA-IR. Furthermore, serum LH and testosterone levels significantly declined. Because AMH levels were positively correlated with both LH and testosterone levels, and LH and testosterone levels were significantly reduced through the use of OC in the combination treatment, serum AMH levels also significantly decreased. In the combination treatment, metformin did not appear to induce an additional change in AMH levels; thus, our findings were similar to those of a previous study . The combined treatment was shown to improve the endocrine disorder status and metabolic aspects and to decrease serum AMH levels in PCOS. We provide additional evidence to support previous reports that AMH concentrations reflect the severity of PCOS [8, 11]. However, the sample size of our study was small, and further studies are needed to confirm the effect of combined treatment on AMH.
In clinical practice, treatment of women who have PCOS with clomiphene (CC) or exogenous gonadotropins for ovulation induction carries a risk of multifollicular development, resulting in ovarian hyperstimulation and multiple pregnancy [35, 36]. Moreover, cancelation of cycles may be required due to either a poor or an excessive ovarian response. If pretreatment with OC and metformin decreases serum AMH concentrations, and if the value of AMH is useful for estimating treatment efficiency, then AMH may facilitate the optimal determination of subsequent ovulation induction with CC or gonadotropins for women with PCOS . Our findings therefore expand the clinical utility of AMH.
The limitations of our study include the small sample size and the short duration of treatment. Further studies with a larger sample size and longer treatment duration are needed to confirm the impacts of these treatments on serum AMH concentrations.