Abstract

PIP: Studies on the role of sex steroids in the feedback control of follicle stimulating hormone (FSH) concentrations in 22-35 year old men are reported. 10 normal volunteers and 8 men undergoing evaluation for azoospermia or oligospermia received steroids by constant infusion for 96 hours at twice the estimated daily production rate of normal men to obtain stable levels in peripheral blood. 15 mg of testosterone increased plasma testosterone and estradiol levels 2-fold and suppressed FSH and luteinizing hormone (LH) approximately 40% during infusion Days 3 and 4. 90 mcg of estradiol/day caused similar suppression of FSH and LH and the addition of 4.5 mg of 17 alpha-hydroxyprogesterone had no additive effect. 7.5 mg of dihydrotestosterone/day produced no detectible changes in FSH or LH. No evidence for a selective effect of any of the steroids on FSH secretion was seen. These data support the concept that although there is a specific seminiferous tubular factor regulating FSH secretion, testicular steroids also modulate FSH secretion.