CALCITONIN AND HUMAN RENAL CALCIUM AND ELECTROLYTE TRANSPORT

While original studies in man and animals suggested that calcitonin in creases renal Ca excretion, subsequent studies in the rat have confirm ed calcitonin as a renal Ca-conserving hormone. In this study three co ncentrations of calcitonin (0.01, 0.1 and 1.0 mg prime and per hour) w ere infused into humans made acutely hypercalcemic to inhibit endogeno us PTH secretion. Calcitonin promptly inhibited the hypercalcemia in a dose-dependent way and also reduced fractional Ca excretion. In addit ion calcitonin, particularly at 0.1 and 1.0 mg concentrations, increas ed absolute Ca and Mg reabsorption, No significant effects of calciton in on Na and K transport were noted with these concentrations; however , the highest calcitonin concentration produced a small but significan t increase in fractional phosphate excretion (0.6 +/- 0.2 to 1.0 +/- 0 .3%; p < 0.05). Creatinine clearance was also increased with the highe st calcitonin concentrations. It is concluded that in man calcitonin l ike PTH is a renal Ca- and Mg-conserving hormone.