Metabolic Clearance Rates of Luteinizing Hormone in Women during Different Phases of the Menstrual Cycle and While Taking an Oral Contraceptive

Abstract

The MCR of human LH (hLH) was determined in five healthy young women by the continuous iv infusion of purified pituitary hLH to steady state levels in serum. Each woman was studied on three occasions: once each during the follicular and luteal phases of the menstrual cycle, and a third time after a brief (8–12 days) course of a combination oral estrogen/progestagen agent to suppress the endogenous production of hLH. The immunoreactive hLH in serum at steady state was indistinguishable from the purified hLH infused in terms of apparent molecular size, as determined by Sephadex G-100 gel filtration and parallel dose-inhibition curves in the hLH RIA. Steady state levels of hLH in serum were achieved in 60-80 min and ranged from 660–1330 ng/ml (LER-907 standard). The MCR of hLH was slightly more rapid in the luteal phase [22.8 ± 2.0 ml/min-m² (mean ± SEM)[ than in the follicular phase (20.5 ± 1.6 ml/min-m²; P < 0.02, by paired t test). The MCR of hLH during estrogen/progestagen administration (22.2 ± 1.6 ml/minm²) was not significantly different from that during either the follicular or luteal phase. Urinary hLH immunoreactivity was analyzed in the women; most of the excreted hLH immunoreactivity was similar to the administered purified hLH by apparent size on gel filtration. From quantitative urine collections in two of the women, the renal clearance rate of hLH was estimated to be 2.9 ± 0.5 ml/min-m². We conclude that the MCR of hLH in healthy premenopausal women is about 20–25 ml/min-m²;it may be slightly more rapid in the luteal phase than in the follicular phase of the menstrual cycle. The MCR of hLH is not appreciably affected by the administration of a combination estrogen/progestagen agent. Renal excretion appears to account for about 12% of the disposal of hLH immunoreactivity. (J Clin Endocrinol Metab55: 654,1982)