Intraovarian regulation: the IGF-I example.

A large body of information now supports the existence of an intraovarian system of insulin-like growth factors (IGFs) replete with ligands, receptors, and binding proteins. The intraovarian IGF system is most likely concerned with the amplification of gonadotrophin hormonal action, other potential regulatory roles remaining speculative at this time. There is every reason to believe that work in the next few years will yield the insight necessary to establish whether or not IGFs are truly indispensable to ovarian function; this remains to be demonstrated through selective ablation of ovarian IGF-I gene expression and the examination of the impact of such manipulation on reproductive potential.