MELATONIN AND GONADOTROPIN-SECRETION AFTER ACUTE EXERCISE IN PHYSICALLY ACTIVE MALES

Serum concentrations of luteinizing hormone (LH), follicle stimulating hormone, testosterone (T) and melatonin were measured in seven physic ally active male volunteers after exercise on a treadmill using the Br uce protocol. Measurements were made on blood samples obtained before exercise, within 30 s after exercise, at 15 min after exercise, and su bsequently at 30-min intervals after exercise for a total duration of 180 min. Serum LH concentration fell from a peak post-exercise level o f 15.7 (4.7) IU . l-1 [mean (SD)] to a nadir of 10. 3 (2.4) IU . l-1 ( P < 0.004). Nadir values in individual volunteers were seen between 60 and 150 min after exercise. This fall in serum LH was paralleled by a similar fall in the concentration of serum T. Serum melatonin concent rations did not change significantly after exercise. It is concluded t hat melatonin, despite is reported anti-gonadotropic properties, does not play a role in the depression of serum LH after acute strenuous ex ercise in physically active males.