Steroidogenesis in human follicles approaching ovulation as judged from assays of follicular fluid.

Human chorionic gonadotrophin (HCG) was given to patients at mid-cycle before the endogenous LH surge. Graafian follicles were aspirated 32-33 h later, before ovulation was expected, and the levels of several steroids in follicular fluid and in matching serum samples were measured by radioimmunoassay. Two types of Graafian follicle were identified at laparoscopy , based on the nature of the oocyte, granulosa cells and follicular fluid withdrawn from the follicles. Some were large, preovulatory and presumably becoming luteinized while others were generally smaller, non-ovulatory and still growing. The concentrations of dehydroepiandrosterone (DHEA) and 17alpha-hydroxypregnenolone (delta5 intermediates), androstenedione and testosterone were higher in non-ovulatory follicles, whereas large follicles usually contained high levels of progesterone, 17alpha-hydroxyprogesterone, pregnenolone and oestradiol-17beta. A cluster analysis of these data grouped follicles into two distinct clusters, which accorded with their identification as ovulatory or non-ovulatory at laparoscopy. Levels of progesterone, 17alpha-hydroxyprogesterone and oestradiol-17beta in follicular fluid were high in preovulatory follicles in comparison with plasma. Results in two patients indicated that plasma levels of these steroids were determined by the preovulatory follicle. Levels of plasma delta5 steroids were closer to follicular fluid concentrations, whereas DHEA was higher in plasma. The role of the theca and granulosa is discussed in relation to the synthesis of progesterone and oestradiol-17beta in follicles as ovulation approaches.