Steroid production in cultured thecal cells obtained from human ovarian follicles.

During follicular maturation there is a co-ordinated hormonal regulation of the theca and granulosa cells. It is generally believed that granulosa cell proliferation and differentiation are promoted mainly by follicle stimulating hormone (FSH) and that luteinizing hormone (LH) regulates the function of the theca cells. The aim of the present study was to examine the effect of LH/human chorionic gonadotrophin (HCG) on steroid production in human thecal cells. Isolated follicles (5-20 mm) were obtained during the follicular phase of the menstrual cycle in 10 women undergoing gynaecological laparotomy for reasons unrelated to ovarian pathology. The leading follicle(s) was excised and dispersed cells of the theca interna layer were isolated through combined mechanical and enzymatic techniques. The thecal cells were cultured 4-6 days with and without LH/HCG. Medium levels of androstenedione, testosterone and progesterone were measured by radioimmunoassay. Isolated thecal cells, cultured for 6 days, showed a high sensitivity to stimulation by LH/HCG. Steroid secretion was highest during days 0-2 and then declined gradually. LH/HCG stimulated steroid production in a dose-dependent way with the maximal stimulatory effect of LH at a concentration of 1-10 ng/ml, and of HCG at 0.01-0.1 IU/ml. The important question, especially in clinical situations, of the optimal level of LH for normal follicular maturation, remains to be answered. The present study is compatible with the view that thecal cell steroidogenesis in vivo is close to maximally stimulated by normal basal LH levels.