Hypercalcemia in Children with Disorders of Calcium and Phosphate Metabolism During Long-Term Treatment with 1,25-Dihydroxyvitamin-D3

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Abstract
Forty-two children received 1,25-dihydroxy-vitamin-D3 for treatment of disorders in calcium and phosphate metabolism secondary to chronic renal insufficiency (n = 29), sex-linked dominant hypophosphatemic rickets (n = 9), hypoparathyroidism (n = 2), and pseudohypoparathyroidism (n = 2). Serum calcium, phosphate, and creatinine concentrations were measured monthly for a mean of 26 months and a total of 1,079.5 patient-months. Patients with renal osteodystrophy manifested hypercalcemia (>11 mg/dL) once in every 13 months of treatment on the average. Of three children with hypophosphatemic rickets who experienced hypercalcemia, two proved to have tertiary hyperparathyroidism. Among children with hypoparathyroidism and pseudohypoparathyroidism, three episodes of hypercalcemia were observed during 124.5 patient-months, an incidence of one hypercalcemic episode per 39 treatment months. Renal function, as represented by reciprocals of serum creatinine determined retrospectively for a mean of 22 months before and prospectively for a mean of 26 months after initiation of 1,25-dihydroxyvitamin-D3 treatment, underwent no significant changes except in seven of 29 children with chronic renal insufficiency, six of whose rate of renal function deterioration increased on the treatment and one whose rate decreased. With one exception, hypercalcemia was associated in all cases with accelerated renal function deterioration. Before and after initiation of treatment with 1,25-dihydroxyvitamin-D3 the mean calcium x phosphate solubility products were 42.9 and 47.2, respectively. Values less than 60 are accepted as normal. Hypercalcemia is an occasional concomitant of such treatment and a more rapid deterioration of renal function may occur in some of the patients treated with 1,25-dihydroxyvitamin-D3. Thus, careful monitoring of concentrations of serum calcium, phosphate, and creatinine must accompany 1,25-dihydroxy-vitamin-D3 therapy.