Idiopathic infantile hypercalcemia: rapid response to treatment with calcitonin.

We report on a 7-week-old infant with idiopathic hypercalcemia, hypercalciuria and nephrocalcinosis. At the time of admission, serum concentrations of parathyroid hormone and 1,25(OH)2D3 were found to be inadequately high, and those of calcitonin and 24,25(OH)2D3 too low, relative to the hypercalcemia. Treatment with calcitonin normalized serum calcium concentrations within 4 days, and a 3-week course of thiazides combined with a decreased dietary calcium:phosphorus ratio corrected the hypercalciuria. A repeat profile of the calcium-regulating hormones done at the age of 5.5 months was normal. Based on the clinical course and the hormonal profiles, we hypothesize that the idiopathic infantile hypercalcemia in this patient could have resulted from a generalized maturational delay of calcium homeostasis. Treatment with calcitonin, therefore, seems to be the most appropriate way to control the hypercalcemia.