**4. The predictive value of AMH for oocyte yield in endometriosis**

Although, circulating AMH levels are considered, in general, a valuable tool for the prediction of the ovarian response to COS, in endometriosis its predictive value might be affected. This hypothesis is supported by studies that demonstrated that AMH production could be influenced independently of the ovarian reserve. However, its predictive value in endometriosis is largely unknown.

Yoo et al. showed that serum AMH level is a significant predictor of oocytes yield in endometriosis patients performing IVF [14], while Wahd et al. found no predictive value of AMH in patients with advanced endometriosis [36]. The lack of the predictive ability of AMH was confirmed in another study that analyzed only patients with endometrioma [26]. The design of the studies and differences in study populations might explain the divergent results of the studies, being possible that more severe endometriosis and endometrioma, especially bigger ones to significantly disrupt the relationship between AMH and ovarian reserve.

Despite the negative relationship between endometriosis and circulating AMH reported by several studies, two reports found an increasing serum AMH level with endometrioma size [37, 38]. If this finding will be confirmed by future studies, a possible explanation is a different impact of endometrioma on AMH production

#### *The Impact of Endometriosis on Controlled Ovarian Stimulation Outcome DOI: http://dx.doi.org/10.5772/intechopen.101588*

from the other endometriosis lesions. The authors hypothesized that the increasing AMH level could be due to higher discharge in the systemic circulation by increased ovarian blood flow as a consequence of the inflammation and neoangiogenesis found in endometriosis. In support of this hypothesis are the studies that reported increased levels of vascular endothelial growth factor (VEGF) in serum and peritoneal fluid of patients with endometriosis [39]. These increased levels are correlated with microvessels density in the endometriotic tissue [40]. Thus, increased vascularization might contribute to disproportionately higher serum AMH levels in comparison with ovarian reserve, therefore affecting its value as a predictor of COS response in endometriosis. However, this mechanism could be particular to endometrioma as suggested by a study that showed that the gene expression of VEGF is increased only in patients with endometrioma and not in those with deep infiltrating endometriosis [41].
