Propranolol and the hypercalcaemia of thyrotoxicosis

The effect of propranolol on serum calcium was studied in 25 patients with thyrotoxicosis including 5 with hypercalcemia. In patients with hypercalcaemia iv propranolol significantly reduced serum calcium. Oral therapy 160 mg/day reduced calcium non-significantly from 2.72 +/- 0.09 (mean +/- SD) to 2.59 +/- 0.13 mmol/l, however on 320 mg/day the reduction (to 2.5 +/- 0.15 mmol/l) was significant. In normocalcaemic patients oral propranolol did not influence serum calcium. Both in hyper- and normocalcemic thyrotoxic patients propranolol increased (P less than 0.01) serum phosphate.