Autocrine and paracrine regulation of the ovary

Abstract

Ovarian follicular development and regression is a continuous and cyclic process that depends on a number of endocrine, paracrine, and autocrine signals. Although many of the factors involved in follicular growth have been characterized, it remains unknown why one or more, depending on species, preovulatory follicle(s) emerge as dominant and the others regress. It is postulated that the selected dominant follicle(s) possesses a higher sensitivity to FSH due to increased expression of FSH receptors. As a result, increases in estradiol and inhibin trigger a negative feedback mechanism that prevents the other follicles from continuing their development. The ovarian theca and granulosa cells also play an important role, since they produce steroid hormones required for normal follicular growth. In addition, ovarian growth factors, cytokines, and neuropeptides participate as regulators of follicular growth and in the formation of the ovarian cell compartments as well. © 2009 Springer-Verlag US.