Effects of Single and Multiple Injections of Synthetic GnRH on Serum LH, FSH and Testosterone in Young and Old Male Rats

Abstract

Male Wistar rats, 21 months old, had significantly lower basal serum FSH, LH and testosterone levels than 4 month old male rats. A single injection of 450 ng GnRH/100 g body weight was equally effective in old and young male rats in raising serum LH and FSH levels. However, 9 consecutive injections of 50 ng GnRH/100 g body weight given every 26 min resulted in significantly smaller increases in serum LH, FSH and testosterone in old than in young male rats. The diminished effects of multiple GnRH injections on LH, FSH and testosterone release in old male rats may be due to smaller pools of releasable gonadotropins in the pituitary.