Effects of acute and chronic hypercalcemia on parathyroid function and circulating parathyroid hormone molecular forms

Bas et al. (1), in this issue, have demonstrated that acute hypercalcemic clamp over 2 h in rabbits reduces the subsequent intact (I) parathyroid hormone (PTH) response to hypocalcemia by 50%, while chronic hypercalcemia, secondary to experimental renal failure in the same animal model, fails to reduce the I-PTH response to hypocalcemia. These results raise questions about the acute and chronic influence of calcium concentration on parathyroid function and on circulating PTH molecular forms. To understand and appropriately discuss these differences, it is necessary to review