The effect of gonadotropin-releasing hormone on ovarian estradiol secretion

The present study was undertaken to determine if more than one dose of GnRh is necessary to induce luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion that is sufficient to cause a significant increase in circulating estradiol (E2) levels. Thirty-four women were studied. Of these, eight control women were studied in the early follicular phase (baseline E2, 48 +/- 4.5 pg/ml); eight patients had secondary amenorrhea caused by hypothalamic dysfunction (baseline E2, 52.0 +/- pg/ml), seven had secondary amenorrhea caused by hypothalamic pituitary failure (baseline E2, 21 +/- 2.5 pg/ml), and 11 women had amenorrhea, galactorrhea, and hyperprolactinemia (baseline E2, 16.5 +/- 3 pg/ml and baseline prolactin, 443 +/- 98 ng/ml). An initial intravenous bolus of 150 microgram of gonadotropin-releasing hormone was followed 2 hours later by a smaller dose of 50 microgram. Thirty minutes following the first and second doses of GnRH, plasma LH and FSH increased significantly in all subjects. The initial increase of LH and FSH did not result in an increase in the plasmma E2 levels in any of the subjects. However, following the second gonadotropin peak, a significant increase in plasma E2 values was observed at 4 hours in all subjects (P less than 0.01). It can be concluded that (1) GnRH can be used to induce ovarian stimulation in normal women as well as in amenorrheic patients with low or normal baseline E2 levels as long as a sequential increase in LH and FSH can be elicited and (2) hyperprolactinemia does not interfere with ovarian E2 synthesis.