COMPARISON OF GROWTH-HORMONE AND INSULIN-LIKE GROWTH-FACTOR-I REGULATION OF ESTRADIOL AND PROGESTERONE PRODUCTION IN HUMAN LUTEINIZED GRANULOSA-CELLS

Growth hormone (GH) appears to affect the timing of puberty in childre n. The effects of GH on puberty may be related to direct GH action on ovarian function or may be mediated by IGF-I. To determine the likelih ood that GH has direct effects on ovarian function, we compared the ab ility of GH and IGF-I to increase luteinized granulosa cell steroidoge nesis in the absence and presence of gonadotropins. Cells were obtaine d from women undergoing in vitro fertilization for tubal disorders or male factor infertility and were placed in static culture. GH alone fa iled to alter progesterone or estradiol accumulation in the medium of cultured luteinized granulosa cells. IGF-I produced no increase in pro gesterone accumulation but increased estradiol accumulation 5.6-fold c ompared with cells treated with vehicle. The combination of GH and FSH produced an 0.83-fold increase in estradiol accumulation, whereas the combination of IGF-I and FSH resulted in a 2.9-fold increase in estra diol accumulation above FSH alone. Thus the direct effects of GK on gr anulosa cell steroid synthesis are modest compared with those of IGP-I . If GH has an effect on ovarian development at puberty, it is likely to be mediated by a GK-induced increase in circulating IGF-I.