Metabolic effects of propranolol in thyrotoxicosis. I. Nitrogen, calcium, and hydroxyproline.

The effect of propranolol on the hypermetabolism of thyrotoxicosis was investigated in eight subjects with diffuse toxic goiter. After equilibration on a constant nitrogen, calcium, and hydroxproline intake, nitrogen balance was determined before and during propranolol therapy prior to subtotal thyroidectomy and compared to similar data obtained in seven of the patients following surgically induced euthyroidism. Propranolol administration was associated with clinical amelioration and a rapid, statistically significant, improvement in nitrogen retention. A slight additional improvement in retention was noted in the postoperative euthyroid state. Oxygen consumption, measured serially in four patients, was not significantly changed by propranolol. Urinary loss of calcium, phosphorus, and hydroxyproline was unaffected by propranolol, but excretion of these substances was sharply reduced in the subjects restudied postoperatively. These data offer a evidence of a previously unreported nitrogen sparing effect of oral propranolol during its short-term administration in thyrotoxic man.