1. The metabolic responses to an oral glucose tolerance test (100 g) and an intravenous insulin provocation test (0·1 i.u./kg) were studied in nine control subjects and nine patients with Huntington's chorea. 2. Plasma glucose responses to these stimuli were identical in both groups. 3. High fasting concentrations of non-esterified fatty acid (NEFA) were recorded in the choreic patients when compared with control subjects. This difference was maintained under hypoglycaemic conditions. However, during hyperglycaemia the differences in NEFA concentrations between the groups was abolished. 4. Total plasma tryptophan concentrations were equal in the two groups. Free plasma tryptophan, however, was markedly reduced in the choreic group, and this appeared to be a result of a disturbed relationship between free tryptophan and NEFA concentrations. The abnormalities in free tryptophan values were sensitive to plasma glucose concentrations, as hyperglycaemic conditions markedly reduced the differences between the choreic and control group. 5. Patients with Huntington's chorea showed reduced fasting plasma concentrations of leucine, isoleucine and valine.

1. Growth hormone secretion was assessed in nine control subjects and nine patients with Huntington's chorea. 2. Early-morning fasting plasma samples from patients with Huntington's chorea contained abnormally high concentrations of growth hormone. 3. The suppression of growth hormone after oral glucose in choreic patients, unlike the control subjects, occurred at irregular intervals after the glucose was given and was followed, again at irregular intervals, by an exaggerated rebound phase. 4. The response to intravenous insulin was not markedly abnormal in choreic patients. However, there was a significant increase in the rate of rise of growth hormone concentration in the first half an hour after the insulin injection when compared with control subjects.