Gonadotropic control of ovarian follicular growth and development

Developmenr-related paracrine cues that sensitize follicles to follicle sti mulating hormone (FSH) and luteinizing hormone (LH) are crucial to the emer gence of a single dominant follicle in each ovulatory menstrual cycle. Sex steroids, insulin-like growth factors and members of the transforming growt h factor-beta superfamily are keg; players in the follicular paracrine syst em. FSH ac ts through membrane-associated granulosa cell receptors (FSHR) t o stimulate granulosa cell proliferation and differentiation. The most resp onsive Follicle at the beginning of the cycle is the first to produce estro gen and express granulosa cell LHR. Paracrine signalling activated by FSH a nd LH sustains growth and oestrogen secretion until an ovulation-inducing L H surge is discharged by the pituitary gland. LH then reprogrammes granulos a cell function. leading to terminal differentiation (luteinization) ruptur e of the follicle wail, and release of the fertilizable egg. The genes regu lated by the LH surge orchestrate profound changes in sex steroid productio n, metabolism and action which are necessary for ovulation. Preovulatory gr anulosa cells also increase their ability to metabolise cortisone to cortis ol. which may be part of a local anti-inflammatory mechanism to promote rap id healing of the ruptured ovarian surface. (C) 2001 Elsevier Science Irela nd Ltd. All rights reserved.