Follicle Selection

BIOLOGY OF REPRODUCTION 65, 655–659 (2001)

M i n i r ev i ew
Follicle Selection in Primates: ‘‘Many Are Called but Few Are Chosen’’1
Anthony J. Zeleznik2
Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
ABSTRACT
During the follicular phase of humans and most nonhuman primates, a single preovulatory follicle usuallymatures each menstrual cycle. The observation that numerous preovulatory follicles may be stimulated to mature when exogenous gonadotropins are administered indicates that there must be a precise and highly reproducible mechanism by which only one of the many follicles capable of ovulating actually does so. The goal of this review is to summarize past and current research which indicates that follicleselection in primates is the result of an exquisitely sensitive interplay between gonadotropin secretion by the pituitary gland, steroid production by the ovary, and maturation-dependent alterations of the ovary’s responsiveness to gonadotropins.

and ‘‘How is the selected follicle spared from its own inhibition?’’
CESSATION OF PREOVULATORY FOLLICULAR DEVELOPMENT DURING THE LUTEAL PHASEfollicle-stimulating hormone, luteinizing hormone, menstrual cycle, ovary

INTRODUCTION

The goal of this review is to summarize the current views regarding the regulation of the primate menstrual cycle with particular reference to the physiological and cellular mechanisms involved in the initiation of preovulatory follicular development and the selection of a single preovulatory follicle. Forthis purpose, the review will focus on the following: the cessation of preovulatory follicular growth during the luteal phase of the menstrual cycle, the initiation of preovulatory follicular growth during the early through midfollicular phase of the menstrual cycle, and the selection of the preovulatory follicle during mid- through late follicular phase of the menstrual cycle. This reviewsummarizes early work that has also been reviewed elsewhere [1] as well as more recent studies by this laboratory and others. It will focus on answering two simple questions, the answers of which are key to the understanding of follicle selection: ‘‘How does the maturing follicle inhibit the development of less mature follicles?’’
The author’s research reported in this review was supported by NationalInstitutes of Health grants HD 12014, HD 16842, HD 08610, and Research Career Development Award HD 00531. 2 Correspondence: Anthony J. Zeleznik, Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, S327 Biomedical Science Tower, 3500 Terrace St., Pittsburgh, PA 15261. FAX: 412 383 7159; e-mail: zeleznik @pitt.edu
1

Received: 13 October 2000. First decision: 14November 2000. Accepted: 19 March 2001. 2001 by the Society for the Study of Reproduction, Inc. ISSN: 0006-3363. http://www.biolreprod.org

Unlike other species (cows, horses, and sheep) follicular development does not progress beyond the early antral stages during the luteal phase of the menstrual cycle of monkeys and humans indicating that, in some manner, the presence of a functional corpusluteum inhibits antral follicular development. This inhibition could either be direct or indirect. Direct inhibition would involve a mechanism whereby secretions of the corpus luteum locally inhibit the maturation of preovulatory follicular development. An indirect mechanism would involve feedback inhibition of gonadotropin secretion by secretory products of the corpus luteum. Evidence for a directeffect of the corpus luteum in inhibiting follicular development came from the studies in monkeys by Goodman, Hodgen, and coworkers [2], which demonstrated that removal of the corpus luteum during the midluteal phase of the menstrual cycle resulted in the initiation of follicular development in the absence of a statistically significant increase in the plasma concentrations of FSH and LH. This...