Variations in plasma glucose, insulin, growth hormone and catecholamines in response to insulin in trained and non-trained subjects.

Previous studies have shown a reduced insulin secretion in trained subjects challenged by a glucose load. In the present study the response to insulin of 8 athletes was compared to that of 8 non-trained subjects. The disappearance of plasma insulin was not different between the two groups, but the level of hypoglycemia was greater in the trained subjects. The injection of insulin increased the plasma levels of epinephrine (E) and norepinephrine (NE) in both groups of subjects, but the raise in E was greater in the trained subjects. Similarly, the increase of growth hormone (GH) was greater in the trained subjects. These findings substantiate previous results showing a decreased insulinic index and an increased insulin binding to monocytes in trained subjects. It is also suggested that the enhanced E and GH secretion found in trained subjects injected with insulin, is possibly related to the greater fall in plasma glucose in the trained subjects compared to the non-trained subjects.