Dr. Pieper et al., VOLUNTARY EXERCISE INCREASES GONADOTROPIN-SECRETION IN MALE GOLDEN-HAMSTERS, American journal of physiology. Regulatory, integrative and comparative physiology, 38(1), 1995, pp. 179-185
To determine the effect of voluntary exercise and food restriction on
reproductive hormone secretion, 48 adult male hamsters were placed in
cages with (EX) or without (SED) running wheels. One-half of the anima
ls in each exercise group was fed ad libitum, and the other half was f
ood restricted to reduce their body weight to 90 g over 4 wk. After 10
wk, the EX ad libitum-fed group had much larger testes and much highe
r serum follicle-stimulating hormone and testosterone levels than the
other three groups, but these values in the EX food-restricted hamster
s were similar to those in the SED food-restricted group. In experimen
t 2, 20 adult male hamsters were castrated and later implanted with si
licone rubber capsules containing testosterone. Two weeks after implan
tation of the capsules, the serum follicle-stimulating hormone levels
were higher in the EX than in the SED group of testosterone-treated ha
msters, but not in animals receiving blank capsules. These data sugges
t that exercise increases gonadotropin secretion by inhibiting the neg
ative feedback of testosterone.