Exaggerated growth hormone response to arginine infusion in Huntington's disease.

Growth hormone regulation was studied in 10 patients with Huntington's disease after intravenous administration of arginine. In 20 control subjects arginine infusion resulted in a rise of plasma growth hormone levels from a mean baseline value of 3.2+/-0.6 ng/ml to a peak level of 17.6+/-2.7 ng/ml at 60 min. Growth hormone rise in the majority of patients with Huntington's disease was clearly intact and significantly greater than normal in magnitude, increasing from the baseline level of 2.6+/-0.5 ng/ml to a peak level of 28.3+/-3.7 ng/ml at 60 min (P = less than 0.05). Carbohydrate tolerance of these patients was previously examined, and 4 with normal glucose tolerance and normal insulin responses to arginine infusion had growth hormone levels significantly higher than controls at 30 min. Six patients with impaired carbohydrate tolerance and exaggerated insulin responses to arginine had significantly higher growth hormone responses at 30 min and also at 60 min. Neuronal degeneration of several hypothalamic nuclei has been reported in Huntington's disease. The observations that growth hormone responds in an exaggerated fashion to stimulation by arginine infusion or falling glucose levels as previously described may be explained by intrahypothalamic dysfunction such as impairment of somatostatin secretion.