Comparative Effect of Calcium and of the Adrenergic System on Calcitonin Secretion in Man*

Abstract

The effects of adrenergic agents on immunoreactive calcitonin (iCT) secretion in normal man were studied and the time course and magnitude of these effects were compared with those caused by modifying Ca ion concentration. Ca infusion (15 mg Ca++/kg i.v. in 4 h) significantly increased plasma iCT within 1 h, reaching 140 .+-. 8% of baseline at 4 h. EDTA (50 mg/kg i.v. in 2 h) significantly decreased plasma iCT within 15 min, with nadir value of 53 .+-. 4.9% of baseline at 2 h. The .beta.-adrenergic agonist, isoproterenol, significantly increased plasma iCT within 5 min, reaching 136 .+-. 5.9% of baseline at 30 min. The .alpha.-adrenergic antagonist, phentolamine, significantly increased iCT within 15 min, reaching 132 .+-. 8.6% of baseline at 45 min. The .beta.-adrenergic antagonist, propranolol, significantly suppressed iCT within 15 min, reaching 51.8 .+-. 6.3% of baseline at 2 h. The adrenergic system (without induced change in serum Ca) can modify CT secretion to as great a degree as can change in Ca ion concentration induced by standard Ca and EDTA infusion tests and even basal secretion of CT can be modified by adrenergic influences. The adrenergic system is an effective modifier of CT secretion and the adrenergic system, as well as Ca ion concentration, may play an important physiological role in control of CT secretion in man.