Pituitary-ovarian dysfunction and endometriosis

Significant association between endometriosis, including minor endometriosis, and infertility (or strictly subfertility) is shown by prevalence studies, but a causal relationship has not been established. This review focuses on evidence for pituitary-ovarian dysfunction as a cause for the subfertility. A methodological problem is lack of fertile controls with endometriosis. Group comparison with tubal infertility cases as controls have demonstrated: impaired follicular growth, reduction in circulating oestradiol concentrations during the pre-ovulatory phase and of oestradiol and progesterone during the early luteal phase, and disturbed luteinizing hormone (LH) surge patterns. Reduction in LH concentrations in pre-ovulatory follicular fluid has also been found, and granulosa cells collected at the same time have demonstrated impaired steroidogenic capacity in vitro, but these were not consistently proven findings. Pooled data from published studies show significantly reduced oocyte fertilization rates (49%) compared with controls (69%), even after maximal stimulation with exogenous follicle stimulating hormone (FSH) and human chorionic gonadotrophin (HCG) (54 versus 69%). The implantation rate is also slightly (though significantly) reduced (11 versus 13%). The findings suggest an inherent disorder of follicular function, with LH surge impairment probably being a secondary phenomenon. The resulting reduction in the chance of fertilization of the oocyte would contribute substantially to the subfertility associated with endometriosis. It seems that the benefit of in-vitro fertilization is gained through the excessive number of oocytes obtained by stimulation.