Luteinizing hormone-releasing factor (LRF) in plasma of postmenopausal women.

Abstract

ABSTRACT To determine whether estrogen deficiency in the human leads to increased secretion of luteinizing hormone-releasing factor (LRF), bioassayable LRF activity was estimated by a semi-quantitative assay in extracts of peripheral plasma taken at random from 22 postmenopausal women whose plasma LH levels ranged from 2.7 to 22.3 ng/ml. Seven of the 36 samples tested contained LRF activity (expressed as increment in plasma LH in receipient assay rats) which was more than 3 standard deviations greater than the mean LRF activity in 26 plasma samples from 17 women during the pre- or postovulatory phase of the menstrual cycle. These findings show that LRF is detectable in the blood of some postmenopausal women. In such women, LH is also secreted episodically as shown by cyclic fluctuations in LH levels in multiple plasma samples from 4 menopausal women drawn at 10-min intervals over a 150–190 min period. In 36 plasma samples from menopausal women assayed for both LRF and LH, elevation of LRF activity occurre...