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 recr uitment of resting, primordial follicles into the actively growing pool. He althy, random-cycling female rhesus monkeys were treated with testosterone, dihydrotestosterone (DHT), or vehicle for 3-10 days, after which ovaries w ere collected for histological analysis. The first stage of follicle growth is the formation of the primary follicle, consisting of an oocyte surround ed by a single layer of cuboidal granulosa cells. The number of primary fol licles was significantly increased over time in testosterone-treated animal s. In situ hybridization showed that androgen treatment resulted in an incr ease 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 comparabl e to those of testosterone, showing that these are androgen receptor-mediat ed phenomena. These data show that androgens promote initiation of primordi al follicle growth and implicate oocyte-derived IGF-I in this activation pr ocess.