Androgens Promote Oocyte Insulin-Like Growth Factor I Expression and Initiation of Follicle Development in the Primate Ovary

In the study reported here, we investigated the effect of androgens on recruitment of resting, primordial follicles into the actively growing pool. Healthy, random-cycling female rhesus monkeys were treated with testosterone, dihydrotestosterone (DHT), or vehicle for 3–10 days, after which ovaries were collected for histological analysis. The first stage of follicle growth is the formation of the primary follicle, consisting of an oocyte surrounded by a single layer of cuboidal granulosa cells. The number of primary follicles was significantly increased over time in testosterone-treated animals. In situ hybridization showed that androgen treatment resulted in an increase to 3-fold in insulin-like growth factor I (IGF-I) and to 5-fold in IGF-I receptor mRNA in primordial follicle oocytes. DHT effects were comparable to those of testosterone, showing that these are androgen receptor-mediated phenomena. These data show that androgens promote initiation of primordial follicle growth and implicate oocyte-derived IGF-I in this activation process.