EFFECT OF SERUM PROGESTERONE CONCENTRATION ON PITUITARY LUTEINIZING-HORMONE RELEASE IN POSTMENOPAUSAL WOMEN

We have previously shown that estradiol-17 beta (E(2)) will induce a pituitary luteinizing hormone (LH) surge in postmenopausal women. The current study was designed to evaluate dose response of progesterone (P) on the initiation, augmentation, or inhibition of pituitary LH release in postmenopausal women. Nine healthy postmenopausal women were administered transdermal E(2), 0.05 mg per day for 1 week, followed by 0.20 mg per day for 3 days. In a random assignment, the volunteers each were given one of the three doses of P (12.5, 25.0, and 50.0 mg intramuscularly) daily during the 0.20-mg estrogen administration. There was a washout period of 2 weeks between each of the three P treatment regimens. A pituitary LH surge was induced in five volunteers with all three regimens. The mean time to the initiation of the LH surge was 0.55 +/- 0.32 days, the peak LH value was found after 0.99 +/- 0.39 days, and the duration of the surge was 1.40 +/- 0.56 days. These data suggest that P advances the LH surge following estrogen priming in postmenopausal women. The dose of administered P did not result in any other changes in pituitary LH release.