CORTISOL, GROWTH HORMONE AND PROLACTIN RESPONSES TO INSULIN-INDUCED HYPOGLYCAEMIA IN HYPERTHYROID PATIENTS BEFORE AND DURING β-ADRENOCEPTOR BLOCKADE

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Abstract
Two .beta.-adrenoceptor blocking agents, metoprolol (.beta.-1-selective) and propranolol (non-selective), were used in the treatment of hyperthyroid patients. The response of pituitary stress hormones to insulin-induced hypoglycemia was investigated before and during .beta.-adrenoceptor blockade. Treatment with metoprolol (n = 10) or propranolol (n = 10) produced no changes in the cortisol or prolactin responses to hypoglycemia. The growth hormone [GH] response remained unaltered during metoprolol treatment. A small, but statistically significant, augmentation of GH response was obtained during propranolol treatment. When 12 subjects, euthyroid after final conventional treatment (surgery, radioiodine or thyrostatic drugs), were re-examined, the cortisol and prolactin responses were unchanged, although GH concentrations reached a slightly higher maximum value (P < 0.01). Treatment with .beta.-blocking agents in hyperthyroid subjects apparently has no clinically important influence on the release of pituitary stress hormones during hypoglycemia.