Abstract
Background. Although chronic hyperandrogenism, a typical feature of polycystic ovary syndrome, is often associated with disturbed reproductive performance, androgens have been shown to promote ovarian follicle growth in shorter exposures. Here, we review the main effects of androgens on the regulation of early folliculogenesis and the potential of their application in improving follicular in vitro growth. Review. Androgens may affect folliculogenesis directly via androgen receptors (ARs) or indirectly through aromatization to estrogen. ARs are highly expressed in the granulosa and theca cells of early stage follicles and slightly expressed in mature follicles. Short-term androgen exposure augments FSH receptor expression in the granulosa cells of developing follicles and enhances the FSH-induced cAMP formation necessary for the transcription of genes involved in the control of follicular cell proliferation and differentiation. AR activation also increases insulin-like growth factor (IGF-1) and its receptor gene expression in the granulosa and theca cells of growing follicles and in the oocytes of primordial follicles, thus facilitating IGF-1 actions in both follicular recruitment and subsequent development. Conclusion. During the early and intermediate stages of follicular maturation, locally produced androgens facilitate the transition of follicles from the dormant to the growing pool as well as their further development.
Highlights
The development of ovarian follicles begins during fetal life with the transformation of primordial germ cells into oocytes enclosed in structures called follicles [1, 2]
Much of the information about the role of sex steroids in ovarian functioning has been obtained in studies directed at the action of estrogens [10,11,12] and progestogens [13,14,15], increasing attention is being devoted to the action of androgen hormones because the activation of the androgen receptor located in follicular cells [16, 17] modulates the expression and activity of important genes for the maintenance of ovarian follicle development [17,18,19]
The results compiled in the present review indicate that during the early and intermediate stages of follicular maturation, when androgen receptors (ARs) expression is more pronounced, the androgens locally produced by the developing follicles facilitate the transcription of genes involved in the control of follicle transition from the reserve pool to the growth pool and of genes involved in the promotion of subsequent follicle development
Summary
The development of ovarian follicles begins during fetal life with the transformation of primordial germ cells into oocytes enclosed in structures called follicles [1, 2]. Much of the information about the role of sex steroids in ovarian functioning has been obtained in studies directed at the action of estrogens [10,11,12] and progestogens [13,14,15], increasing attention is being devoted to the action of androgen hormones because the activation of the androgen receptor located in follicular cells [16, 17] modulates the expression and activity of important genes for the maintenance of ovarian follicle development [17,18,19]. AR activation increases insulin-like growth factor (IGF-1) and its receptor gene expression in the granulosa and theca cells of growing follicles and in the oocytes of primordial follicles, facilitating IGF-1 actions in both follicular recruitment and subsequent development. During the early and intermediate stages of follicular maturation, locally produced androgens facilitate the transition of follicles from the dormant to the growing pool as well as their further development
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