The Metabolic Serum Clearance of GnRH. Relationship to Age, Sex and Male Puberty

UNLABELLED: The MCR of constantly infused synthetic GnRH (1.53 micrograms/min) was studied in relation to age, sex, and male sexual maturation. GnRH was determined by a radioimmunoassay using a specific GnRH antiserum and 125I-GnRH, prepared by the chloramine T technique and purified on Sephadex G 25. Serum LH and FSH were measured by RIA. The results (mean values +/- SEM) of MCR expressed here as ml/min/1.86 m2 showed a statistically significant difference: infants (6-13 yrs) 1170 +/- 79, sexually mature males (22-29 yrs) 639 +/- 28, elderly men (64-79 yrs) 520 +/- 38, sexually mature females (20-24 yrs) follicular phases: 1354 +/- 90, luteal phases: 1736 +/- 242, postmenopausal women (53-74 yrs) 598 +/- 45. We found a linear negative correlation between serum LH and MCR of GnRH in both sexes. During male puberty the MCRLH-RH decreased simultaneously to the stages of pubic hair development. IN CONCLUSION: 1) The MCR of GnRH is a function of age, sex, and sexual maturation, 2) its negative linear correlation with LH in both sexes indicates that the MCR presumably reflects endogenous GnRH levels, 3) the MCRGnRH seem to be subject to endocrine regulation.