Impairment of Growth Hormone and Insulin Secretion in Hyperthyroidism

Abstract. The pattern of growth hormone (GH) and im-munoreactive insulin (IRI) secretion in response to insulin hypoglycaemia, arginine infusion and oral glucose load has been investigated in a group of hyperthyroid subjects. In twenty patients, compared with twenty normal controls, GH secretion was significantly reduced in response to both insulin hypoglycaemia and arginine infusion. Arginine-induced IRI secretion was also clearly decreased. In ten patients who had undergone a 100 g oral glucose load, hyperglycaemia failed to suppress GH levels, which increased paradoxically. Slightly impoverished IRI secretion and impaired glucose tolerance were observed in these subjects. In five patients, re-examined soon after restoration of euthyroidiszn, no significant changes in glucose tolerance and IRI secretion were noted; instead, a slightly improved GH response to the provocative stimuli and the restoration of a normal GH suppression by glucose were observed. – The possibility is emphasized that in hyperthyroidism an enhancement of the catecholamine effect induced by thyroid hormones is involved in the diminished GH and IRI secretion.