Neuroregulation of growth hormone during exercise in children

Physical exercise is an important physiological stimulus to growth hormone (GH) release in man. Many neurotransmitters are involved in GH regulation. We studied the effect of the cholinergic pathway on GH secretion induced by physical exercise. Particularly, we studied the effect of a cholinergic mu scarinic agonist on CH-induced physical exercise, both in children and adul ts. Moreover, we investigated the refractoriness of GH secretion after a se cond physical exercise stimulus. Three different protocols were performed: 1) CH response to physical exercise in children and adults; 2) effect of py ridostigmine on exercise-induced GH secretion in children and adults; 3) GH response to two consecutive exercises in children and adults. Our data sho w that in children CH peak after physical exercise is higher than in adults . Pyridostigmine enhances GH release in children and in adults. Exercise st imulus was able to release GH in the second test only in children, while th e refractory phase did not permit a new GH release in adults, The shift to a modality of neural control of GH secretion peculiar of adults is likely d ue to neuroregulatory mechanisms which may be partly dependent on longterm variation in hormonal milieu.