Hormonal correlates of follicular development in the human ovary

This review summarizes recent studies pertaining to follicular development in the human ovary. Some of these studies were concerned with characterizing the steroidogenic capacity of the individual cell types of the follicle in relation to whether the follicle was healthy or atretic. Other studies covered in this review concern the oocyte and its hormonal environment both in vivo and in vitro, the effects of steroids and gonadotrophins on the steroidogenic potentials of follicle cells and also some endocrine and non-endocrine responses of thecal and granulosa cells after being separated and then recombined in vitro. The data are integrated in relation to the development of a follicle during the follicular phase of the menstrual cycle. The studies on the isolated cellular compartments of the follicle show that the biosynthetic and mitotic or developmental activities of granulosa cells and thecal tissues, and the behaviour of oocytes in vitro, all correlate with the hormonal microenvironments that they were previously exposed to in vivo rather than those in peripheral blood. The data suggest that the levels of steroid in follicular fluid and ovarian venous blood, collagen synthesis in the thecal tissue and mitotic activity of the granulosa cells are all dependent in part on a functional interaction between the thecal and the granulosa cells. It is concluded that the fate of a developing antral follicle centers around its ability to generate an oestrogen-enriched intrafollicular environment while simultaneously secreting both androgens and oestrogens into ovarian-venous blood.