Effects of gonadectomy on hypothalamic obesity in male and female rats.

The effects of ventromedial hypothalamic (VMH) lesions on body weight, body composition, and food intake were examined in gonadally intact and gonadectomized adult rats of both sexes. The most striking finding was that, while gonadectomy only modestly augmented the weight gain following VMH lesions in females, castrated VMH males gained twice as much weight as gonadally intact VMH males. Furthermore, the weight gain of the castrated VMH males was comparable to that seen in VMH females. Thus, castration of males eliminates the sex difference in body weight gain that is ordinarily observed in gonadally intact animals following VMH lesions. The degree of weight gain in all VMH animals correlated highly with the amount of food eaten, and additional body weight of all VMH animals was accounted for by increased body fat.