STUDIES OF INSULIN AND GROWTH HORMONE SECRETION IN HUMAN OBESITY.

Abstract Nine grossly obese individuals were starved for 4 to 14 days to study changes in plasma concentrations of nonesterified fatty acids (NEFA), glucose, growth hormone, and insulin. The effects of glucose administration and insulin-induced hypoglycemia on these plasma constituents were also studied. The obese patients responded to fasting with less of a rise in serum NEFA than nonobese subjects. Their plasma growth hormone concentrations were low throughout starvation. There was no significant change in plasma insulin concentration during fasting, but insulin secretion in response to oral glucose load was greater than normal. Glucose tolerance was impaired by starvation in obese subjects. In obese subjects, the increase in plasma growth hormone concentration following insulin-induced hypoglycemia was significantly smaller than in normal subjects. It is concluded that in obese individuals the rise in plasma free fatty acids and the impairment in carbohydrate tolerance which develop during starvation are not a consequence of low insulin or elevated growth hormone plasma concentrations. The impairment in glucose tolerance which develops after fasting may be a direct consequence of elevated plasma NEFA levels. Also, although not a significant factor in obese subjects, growth hormone may play a significant physiologic role in NEFA mobilization in normal individuals.