The bonnet monkey (Macaca radiata): A model for the study of gonadotropin dynamics during fasting in the human

General Hospital and Harvard Medical School, Boston Postmenopausal women excrete significantly greater quantities of radioimmunoassayable luteinizing hormone (LH) and follicle stimulating hormone (FSH) during fasting than during the control or refeeding periods. The concentrations of these gonadotropins in the serum, however, are not affected. In the present studies, ovariectomized Bonnet monkeys (Macaca radiata) and ovariectomized Sprague-Dawley rats were studied to compare the effects of fasting on gonadotropins dynamics in subhuman primates and rodents. Serum LH and FSH concentrations were not reduced by fasting of monkeys or rats. During a 4-day fast, rats excreted significantly (P ⩽ 0.01) less LH, FSH, Na⁺ , and K⁺ than during prefast or refeeding periods. Monkeys, on the other hand, excreted significantly (P ⩽ 0.025) greater quantities of LH and FSH during the last 2 day of a 4-day fast as compared to prefast and refeeding periods. Like the human, they conserved Na+ and K+ on refeeding. These results indicate that the monkey is a better animal model than the rat with which to study the effects of fasting on gonadotropin excretion in the human.