Growth Hormone and Insulin Levels in Weanling Rats with Ventromedial Hypothalamic Lesions

The effects of bilateral stereotactic electrolytic lesions limited to the ventromedial nucleus (VMN) in weanling female rats were studied with respect to growth, pituitary and plasma growth hormone levels, nutrition and plasma levels of glucose and insulin. The following were observed as a result of VMN lesions: 1) a marked decrease in linear growth with less pronounced changes in body weight, 2) an increase in carcass fat despite no increase in food intake, 3) decreased pituitary growth hormone content and plasma growth hormone levels as measured by radioimmunoassay, 4) increased plasma insulin levels and visible lipemia despite minimal changes in plasma glucose, 5) incomplete suppression of the hyperinsulinemia toward control levels by fasting. It is suggested that the ventromedial nucleus exerts a significant control over growth hormone secretion, presumably through a growth hormone releasing factor, and that its destruction results in growth impairment secondary to a deficiency in growth hormone secretion. In addition, an intact ventromedial nucleus in the weanling rat, as well as in the adult, appears to be required for normal carbohydrate and lipid metabolism. (Endocrinology82: 1125, 1968)