The potential relevance of IGFs to ovarian physiology: Recent developments

As the significance of putative intraovarian regulators became increasingly evident, much of the attention has focused on insulin-like growth factors (IGFs). Indeed, a large body of evidence now suggests the existence of an intraovarian IGF system replete with ligands, receptors, and binding proteins. IGFs have been shown to exert a variety of significant effects at the level of somatic ovarian cells thereby raising the possibility of a meaningful role in vivo. Nonetheless, there is at this time no compelling evidence to indicate that IGFs (or, for that matter, any other putative intraovarian regulator) are indispensable to ovarian function. However, a relatively large body of indirect evidence strongly does support such a possibility. It will be the purpose of the presentation to review key developments in this area in the hope of supporting the notion that ovarian IGFs may serve as amplifiers of gonadotropin hormonal action and that some IGFBPs may possess antigonadotropic properties. Moreover, preliminary evidence will be discussed to support the notion that optimal FSH hormonal action may be contingent upon the bioavailability of endogenously-derived IGFs.