The endocrine environment of the human oocyte

The present discussion of some of the endocrine changes occurring within the follicle over the last 40 h before ovulation is far from comprehensive. For example, no data on the important prostaglandin changes have been included. However, it is hoped that the approach described here, whereby the start of the LH surge is assessed by frequent urine or plasma measurements, and this assessment of the 'age' of the follicle corroborated by the relative ratio of oestradiol to progesterone concentrations, will serve as a useful model in which to assess the dynamic equilibrium existing within the human follicle. Information obtained using this model should allow the components of the intrafollicular milieu to be categorized with respect to their functional role within the follicle. For example, some compounds such as collagenase may have primarily a facilitatory role whilst others such as cAMP may have a direct signalling role. The chronological changes in these compounds could then in turn be correlated with morphological and functional changes in the granulosa, basement membrane, and most importantly, the oocyte itself. Eventually it may be possible to go further and locate the biochemical abnormality in specific types of infertility (e.g. the luteinized unruptured follicle syndrome) or when the oocyte fails to undergo normal embryo development, with the ultimate goal of providing rational methods of treatment for these conditions.