Hypothalamic function in amenorrheic runners.

We have examined temperature regulation in eight amenorrheic runners and gonadotropin response to an opioid antagonist in seven amenorrheic runners, 18 to 29 years of age, running 20 to 70 miles a week. Following equilibration, oral temperature was measured continuously, first in a cold room at 39 degrees F and then in a sauna at 172 degrees F in eight amenorrheic runners, in eight eumenorrheic runners, and in eight control subjects in the early follicular phase of the menstrual cycle. Studies were terminated if a subject's temperature fell below 94 degrees F or rose above 102 degrees F, and all studies were conducted in the afternoon. The rates of temperature change, calculated from total net temperature change divided by elapsed time in the test chamber, were not significantly different among the three groups of women. Seven other amenorrheic runners failed to have any significant changes in luteinizing hormone or follicle-stimulating hormone levels in response to the opioid receptor antagonist naloxone administered as an intravenous infusion at 1.6 mg/hour for 4 hours. If opioids inhibit gonadotropin secretion in exercise-associated amenorrhea, an increase in gonadotropins in response to naloxone would have been anticipated. Although it is possible that the dose of naloxone selected was inappropriate and that temperature responses under other conditions might differ from those of normal women, these data suggest that endogenous opiates do not play a direct role in the amenorrhea associated with exercise and that temperature regulatory centers in the hypothalamus are intact in this disorder, compared with other causes of amenorrhea such as anorexia nervosa. Further studies of hypothalamic function are warranted to test these possibilities.