THE EFFECTS OF FINASTERIDE (PROSCAR) ON HAIR-GROWTH, HAIR CYCLE STAGE, AND SERUM TESTOSTERONE AND DIHYDROTESTOSTERONE IN ADULT MALE AND FEMALE STUMPTAIL MACAQUES (MACACA ARCTOIDES)

Finasteride, a 5 alpha-reductase inhibitor, was administered orally (1 mg/ kg day) for 6 months to six male and five female stumptail macaques. Vehicle was given to five male and five female animals over the same period. of time. Hair weights in a defined 1-in.(2) area of frontal scalp were measured periodically every 1-2 months, and serum was collected for measurement of testosterone and dihydrotestosterone. In addition, scalp biopsies were taken before and 6 months after treatment to evaluate the micromorphometry of hair follicles. Results showed that both male and female serum dihydrotestosterone levels were significantly reduced (60-70%) by finasteride treatment. Both males and females showed statistically significant increases in mean hair weight over the treatment period compared to controls (P = 0.034). In addition, there was a statistically significant increase in mean follicle length (measured histologically in scalp biopsies) compared to baseline in the finasteride-treated animals (P = 0.028). These data show that an inhibition of 5 alpha-reductase in the stumptail macaque can reverse the balding seen with age in both the male and female animals.