Calcitonin and human renal calcium and electrolyte transport

While original studies in man and animals suggested that calcitonin increases renal Ca excretion, subsequent studies in the rat have confirmed calcitonin as a renal Ca-conserving hormone. In this study three concentrations of calcitonin (0.01, 0.1 and 1.0 mg prime and per hour) were infused into humans made acutely hypercalcemic to inhibit endogenous PTH secretion. Calcitonin promptly inhibited the hypercalcemia in a dose-dependent way and also reduced fractional Ca excretion. In addition calcitonin, particularly at 0.1 and 1.0 mg concentrations, increased absolute Ca and Mg reabsorption. No significant effects of calcitonin on Na and K transport were noted with these concentrations; however, the highest calcitonin concentration produced a small but significant increase in fractional phosphate excretion (0.6 +/- 0.2 to 1.0 +/- 0.3%; p < 0.05). Creatinine clearance was also increased with the highest calcitonin concentrations. It is concluded that in man calcitonin like PTH is a renal Ca- and Mg-conserving hormone.