Endorphins and exercise in females: possible connection with reproductive dysfunction

Currently available measurements of beta-endorphin and beta-lipotropin in exercising women are in excellent agreement and indicate a 2-3 fold increase over basal levels. Possible effects of exercise upon the transfer of endorphins from the peripheral circulation to the brain are examined, and evidence is presented that suggests the occurrence of a concomitant exercise-related increase of endorphins in both humoral and central nervous system compartments. Steady-state measurements of circulating luteinizing hormone and follicle-stimulating hormone levels in oligo-amenorrheic athletes, on the other hand, do not agree. It is felt that the lack of consensus may be attributable partly to technical inadequacies and partly to lack of awareness of the need for frequent sampling. The bulk of the findings suggest a tendency for luteinizing hormone levels to be low and follicle-stimulating hormone levels to be normal or low, a pattern compatible with repeated activation of the CRH-ACTH-POMC system as a result of exercise.