Comparative effect of calcium and of the adrenergic system on calcitonin secretion in man

This study evaluated the effects of adrenergic agents on immunoreactive calcitonin (iCT) secretion in normal man, and compared the time course and magnitude of these adrenergic effects with those caused by modifying calcium (Ca) ion concentration. Ca infusion (15 mg Ca++/kg iv in 4 h) significantly increased plasma iCT within 1 h, reaching 140 +/- 8% of baseline at 4 h. EDTA (50 mg/kg iv 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 with 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 with 15 min, reaching 51.8 +/-6.3% of baseline at 2 h. Therefore, 1) 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 2) even basal secretion of CT can be modified by adrenergic influences. These data strongly suggest 1) that the adrenergic system is an effective modifier of CT secretion and 2) that the adrenergic system, as well as Ca ion concentration, may play an improtant physiological role in control of CT secretion in man.