Leptin and IGF-I levels in unconditioned male volunteers after short-term exercise

We have previously shown that serum gonadotropins, particularly LH, decline after acute exercise in male volunteers. The mechanism for this decline is unknown. Plasma leptin and IGF-I concentrations were measured in seven mal e volunteers after acute exercise to exhaustion using the Bruce protocol. L eptin concentrations declined following exercise reaching nadir values 30-1 20 min after exercise. As anticipated, plasma IGF-I concentrations showed a transient rise immediately after exercise falling thereafter to nadir leve ls 60-90 min after exercise before returning towards baseline levels. In vi ew of the previously described decline in gonadotropin release after acute exercise, the decline in plasma leptin levels, perhaps related to the rise in IGF-I, may play a role in exercise-induced inhibition of gonadotropin re lease presumably by inhibition of GnRH secretion. (C) 2000 Elsevier Science Ltd. All rights reserved.