The role of steroids in follicular growth
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BioMed Central
Open Access
Review
The role of steroids in follicular growth Ann E Drummond* Address: Prince Henry's Institute of Medical Research, PO Box 5152, Clayton Victoria 3168, Australia Email: Ann E Drummond* - [email protected] * Corresponding author
Published: 10 April 2006 Reproductive Biology and Endocrinology2006, 4:16
doi:10.1186/1477-7827-4-16
Received: 04 October 2005 Accepted: 10 April 2006
This article is available from: http://www.rbej.com/content/4/1/16 © 2006Drummond; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract The steroidogenic pathway within the ovary gives rise to progestins, androgens and oestrogens, all of which act via specific nuclear receptors to regulate reproductive function and maintain fertility. The role of progestins in follicular growth and development is limited, its action confined largely to ovulation, although direct effects on granulosa cell function have been reported. Consistent with these findings, progesterone receptor knockout mice are infertile because they cannot ovulate. Androgens have been shown to promote early follicular growth, but also to impede follicular development by stimulating atresia and apoptosis. The inability of androgens to transduce a signal in mice lacking androgen receptors culminates in reduced fertility. Oestrogens are known to exert effects on granulosa cell growth and differentiation in association with gonadotrophins. Studies with oestrogen receptor knockouts and oestrogen depleted mice have shown us that oestrogen is essential for folliculogenesis beyond the antral stage and is necessary to maintain the female phenotype of ovarian somatic cells. In summary, the action of steroids within the ovary is based on the developmental status of the follicle. In the absence of any single sex steroid, ovarian function and subsequently fertility, are compromised.
Introduction Follicular development begins during foetal life with the transformation of primordial germ cells into oocytes and their enclosure in structures called follicles. In most mammals, primordial follicles form either before, or in the first few days after birth. Primordial follicles give rise to primary follicles which transform into preantral (secondary follicles) then antral follicles (tertiary follicles) and finally preovulatory, Graafian follicles, in a co-ordinated series of transitions regulated by hormones and local intraovarian factors. The growth and differentiation of follicles from the primordial population is termed folliculogenesis. With the LH surge, Graafian follicles rupture and oocytes are released, leaving the follicular cells to luteinise and form a corpus luteum.
Sex steroids play important roles in the growth and differentiation of reproductive tissues and in the maintenance of ferti
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