Follicular determinants of corpus luteum function in the human ovary.

The corpus luteum is a direct continuation of preovulatory follicle development. Growth and differentiation of a follicle to the preovulatory stage depends on certain endocrine changes taking place within the follicle itself (5). These endocrine changes markedly influence the viability, the rate of proliferation, and the biosynthetic potential of granulosa cells. Therefore, the sequence of endocrine events within the developing antral follicle is likely to be of considerable importance for the formation and secretory activity of the corpus luteum. If granulosa cells in developing antral follicles are exposed to certian hormones in the wrong sequence, the follicle may be prevented from developing into a normal corpus luteum. For example, if granulosa cells in antral follicles are not exposed to FSH, they are unable to generate high levels of oestrogen (Table 1). In the absence of oestrogen, granulosa cells do not increase in number. The same end result may also arise if the granulosa cells are exposed prematurely to elevated levels of LH or to high levels of prolactin: LH blocks granulosa cell mitoses even if the cells are exposed to oestrogen (1, 21); high levels of prolactin in antral fluid are associated with low levels of oestrogen and a reduced rate of granulosa cell proliferation. In women, it is likely that a fully functional corpus luteum is formed from a follicle that was exposed to the most favourable sequence of endocrine changes during its antral stages of development.