Growth Hormone and Cortisol Responses to Insulin-Induced Hypoglycemia in Thyrotoxicosis

Abstract

Plasma growth hormone (GH), plasma cortisol and blood glucose responses to insulin-induced hypoglycemia were measured in 17 patients suffering from Graves' disease of differing clinical severity. Blood glucose and plasma cortisol responses to hypoglycemia were similar in thyrotoxic patients and in normal subjects. GH hyporesponsiveness to hypoglycemia was found in 4 of 9 severely thyrotoxic patients. The mean maximum GH level in these 9 patients was 14 ± 10 ng/ml (mean ± 1 sd); this value was significantly lower (p <0.005) than that recorded in moderately or mildly affected patients (52 ± 30 ng/ml) or in normal subjects (37 ± 19 ng/ml). In the 4 GH hyporesponsive patients a normal response was found after amelioration of the clinical condition by antithyroid therapy. It was concluded that the GH hyporesponsiveness to hypoglycemia was present only in the most severely affected thyrotoxic patients.