Alteraitions of pituitary growth hormone reserve in hypothyroid patients

Responses of growth hormone （GH） to insulin-induced hypoglycemia were observed in 14 patients with primary hypothyroidism and 20 normal controls. Serum peak GH values after hypoglycemia were 18.84±7.17 ng/ml in the patients and 35.31±3.98 ng/ml in the controls. The difference was statistically significant （t=2.157, p＜0.05）. Nine of 14 hypothyroid patients showed lower peak GH values as Compared with the normal ranges. There were negative correlations between the peak GH values and hypothyroid courses or serum TSH values, and positive correlations between the peak GH values and serum T3 values or serum T4 values. Of these patients, 7 were reexamined following a period of thyroid replacement therapy. The peak GH values in these 7 patients were 18.63±10.87 ng/ml before the therapy and 23.19±10.87 ng/ml during thyroid replacement therapy. The difference was statistically significant （t=3.211, p＜0.05）. Our study suggests that pituitary GH reserve in primary hypothyroidism may be decreased in relation to the influence of thyroid hormone deficiency on synthesis and secretion of pituitary GH.