Stimulation of luteinizing hormone secretion by food intake: Evidence against a role for insulin

In adult male rhesus monkeys, 1 day of fasting leads to a profound suppression of LH secretion that is rapidly reversed with refeeding. To test the hypothesis that changes in insulin secretion during fasting and refeeding mediate the changes in LH secretion, blood samples for LH measurement were obtained between 0900-2400 h from adult male rhesus monkeys (n = 9) on 1) a day when monkeys were refed their normal meal after a day of fasting, and 2) a day when monkeys were refed their normal meal, but endogenous insulin secretion was suppressed. Diazoxide (7.5-9.5 mg/kg · h) caused a 40-99% suppression of postmeal insulin secretion. However, no significant differences in LH pulse frequency, pulse amplitude, or mean serum LH levels were detected between control and diazoxide trials, even in animals in which insulin was markedly suppressed. Further, no correlation existed between the degree of insulin suppression and the magnitude of the meal-induced stimulation of LH. We conclude that meal-induced insulin secretion does not provide the stimulus mediating the meal-induced increase in LH secretion.