Rodent Studies on the Potential Relevance of Insulin-Like Growth Factor (IGF-I) to Ovarian Physiology
The recurring process of ovarian follicular growth is an exponential rather than a linear process characterized by substantial dramatic proliferation and differentiation of the granulosa cell. Although the pivotal role(s) of gonadotropins and of gonadal steroids in this explosive agenda is well recognized, the variable fate of follicles subject to comparable gonadotropic support suggests the existence of additional intraovarian regulatory mechanism(s). Among potential novel intraovarian regulators, insulin-like growth factor I (IGF-I) has been receiving increasingly intense scrutiny (1–2). Taken together these studies strongly suggest the existence of an intraovarian autocrine control mechanism, wherein IGF-I may serve as the central signal, and the granulosa cell its site of production, reception, and action. Viewed in this light, IGF-I may promote the growth and/or differentiation of the granulosa cell, acting for the most part as an amplifier of gonadotropin action. Granulosa cell-derived IGF-I may also provide paracrine input to the nearby theca-interstitial cell compartment in the interest of coordinated follicular function.
KeywordsGranulosa Cell Follicular Fluid Human Amniotic Fluid Ovarian Physiology Growth Honnone
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