Inhibition of parathyroid hormone secretion by isoproterenol.

Intravenous infusion of the beta-adrenergic agonist isoproterenol produced a fall in the serum concentration of parathyroid hormone. It also produced a pronounced fall in the serum phosphate concentration, and significant increases in blood glucose and serum insulin concentration and in pulse rate. The fall in serum parathyroid hormone was abolished by beta-adrenergic blockage with propranolol. Oral glucose loads produced a pronounced fall in serum phosphate concentration, comparable to the fall after isoproterenol infusion, but no significant changes in serum parathyroid hormone. It is concluded that the fall in serum parathyroid hormone after isoproterenol is due to a beta-adrenergic effect. It is unknown, if isoproterenol acts directly on the parathyroid hormone secreting cell, or the fall in serum parathyroid hormone is secondary to the effect of isoproterenol on other endocrine glands or the cardiovascular system.