ENHANCED NEUROENDOCRINE RESPONSE TO INSULIN TOLERANCE-TEST PERFORMED UNDER INCREASED AMBIENT-TEMPERATURE

The hypothesis that an increase in ambient temperature modulates neuro endocrine response in clinically used provocative pituitary function t ests was verified. Healthy male volunteers were subjected to insulin t olerance tests in two randomized trials. In the first trial hypoglycem ia was induced by a bolus injection of insulin (0.1 U per kg of BW, iv ) at room temperature. In the second trial, the subjects were exposed to increased ambient temperature for 45 min before insulin injection a nd for 45 min thereafter. The environmental temperature was selected t o increase body temperature less than 1C. Under conditions of increase d temperature basal hormone levels as measured in antecubital venous b lood samples failed to be modified and the hypoglycemia was less sever e. Nevertheless, the responses of most (beta-endorphin, ACTH, prolacti n, catecholamines), but not all (growth hormone, cortisol), hormones t o hypoglycemia were exaggerated. The remarkable increase in ACTH and b eta-endorphin release was not accompanied by concomitant increase of p lasma cortisol response. The sympathetic-adrenomedullary system was si gnificantly activated, which was manifested particularly by enhanced n orepinephrine release. Growth hormone response to hypoglycemia was not modified, while that of prolactin was enhanced. Thus during evaluatio n of neuroendocrine function under clinical conditions, changes in amb ient and body temperature should not be underestimated. (J. Endocrinol . Invest. 21: 412-417, 1998) (C)1998, Editrice Kurtis