FIGURE 5-2 The two-cell, two-gonadotropin principle of ovarian steroid hormone produc tion. During the follicular phase (left panen, luteinizing hormone (LH) controls theca cell granulosa cells to conven androstenedi production of androstenedione, which diffuses into the adjacent granulosa cells and acts as one into estradiol. The requirement for precursor for estradiol biosynthesis. The granulosa cell capacity to convert androstenedione thecal cells, which respond ro LH, and to estradiol is controlled by follicle-stimulating hormone (FSH), After ovulation (right panen, granulosa cells, which respond to FSH, the corpus luteum forms and both theca-lutein and granulosa-lutein cells respond to LH. represents the two-gonadotropin, twoThe theca-lutein cells continue to produce androstenedione, whereas granulosa-lutein cells ceH hypothesis for estrogen biosynthesis greatly increase their capacity to produce progesterone and to convert androstenedione to estradiol. LH and hCG bind to the same LH-hCG receptor. If pregnancy occurs (right pane�, (Short, 1962). As shown in 5-2, human chorionic gonadotropin (hCG) rescues the corpus luteum through their shared LH hCG receptor. Low-density lipoproteins (LOL) are an important source of cholesterol for sion of the antrum of growing follicles.
steroidogenesis, cAMP =cyclic adenosine monophosphate.
The follicle within the cohorr that is most responsive to FSH is likely to be the irst to produce estradiol and initiate expression of LH precise predictor of ovulation. It occurs 34 to 36 hours before receptors. ovum release from the follicle (see Fig. 5-1). LH secretion peaks