Short-Term Modulation of the Androgen Milieu Alters Pulsatile, But Not Exercise- or Growth Hormone (GH)-Releasing Hormone-Stimulated GH Secretion in Healthy Men: Impact of Gonadal Steroid and GH Secretory Changes on Metabolic Outcomes1

Abstract

Gonadal steroids are known to alter GH secretion as well as tissue metabolism. The present study was designed to examine the effects of short term (2- to 3-week) alterations in gonadal steroids on basal pulsatile (nonstimulated) and exercise- and GH-releasing hormone-stimulated GH secretion, urinary nitrogen excretion, and basal and exercise-stimulated oxygen consumption. Two protocols were conducted, which reflect a total of 18 separate studies. In the first paradigm, 5 healthy young men were each studied in a double blind, randomized manner during 3 different gonadal hormone manipulations, in which serum testosterone was varied from hypogonadal (induced by leuprolide) to eugonadal (saline injections) to high levels (testosterone enanthate, 3 mg/kg.week, i.m.). There was a washout period of 8 weeks between treatments. In the second protocol, 3 of the original subjects were studied after 2 weeks of treatment with stanozolol (0.1 mg/kg.day). Two to 3 weeks after the desired changes in serum testosterone, each subject was admitted to the General Clinical Research Center for study. The hypogonadal state (serum testosterone, 33 ng/dL) increased urinary nitrogen loss (by 34%; P < 0.005) and decreased basal metabolic rate (by 12%; P < 0.02) compared with the eugonadal state (testosterone, 796 ng/dL). High dose testosterone (1609 ng/dL) further decreased urinary nitrogen loss over the eugonadal state (by 16%; P < 0.05). Stanozolol yielded the lowest urinary nitrogen excretion of all…