Antispermatogenic effect of Norgestrel in rhesus monkeys.

The effect of norgestrel on spermatogenesis was studied in 6 rhesus monkeys who were injected with 3.5 mg norgestrel daily for 94 days. 6 normal monkeys were used as controls. The genital organs were removed within 24 hours of the last injection and analyzed. Norgestrel administration caused a significant decrease in testis weight (p<.01) in fructose concentration in seminal vesicles (p<.01) and in pituitary and serum gonadotropin content (p<.05 and p<.01). The effect of norgestrel on spermatogenesis was inconsistent and unpredictable with some animals severely affected and others not at all. Though a peripheral anti-androgenic effect is prompted by norgestrel this steroid does not appear to be effective in selective control of spermatogenesis.