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Previous Volume 293:840-844 October 23, 1975 Number 17 Next

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Abstract

In hypoparathyroidism and pseudohypoparathyroidism, pharmacologic doses of vitamin D correct hypocalcemia, but the mechanism is unknown. In two children with hypoparathyroidism and one with pseudohypoparathyroidism we tested the hypothesis that in these conditions there is a defect in synthesis of 1 alpha,25-dihydroxyvitamin D3, the principal active metabolite of vitamin D. In both conditions, minute doses of the metabolite (0.04 to 0.08 mug per kilogram of body weight per day) quickly corrected hypocalcemia and increased intestinal calcium absorption. On the other hand, the effective dose of 25-hydroxyvitamin D3 to maintain normocalcemia was 3 to 4 mug per kilogram per day in the two conditions. Thus, the dosage ratio of 25-hydroxyvitamin D3 to 1 alpha,25-dihydroxyvitamin D3 approximated 100:1. By contrast this ratio was approximately 3:1 in two infants with vitamin D deficiency, a condition in which optimal metabolism of vitamin D would be expected. These findings suggest an impaired conversion of 25-hydroxyvitamin D to 1 alpha,25-dihydroxyvitamin D in both hypoparathyroidism and pseudohypoparathyroidism.

This article has been cited by other articles:

• Mimouni, F., Neumann, V. A., Tsang, R. C., Hollis, B. W. (1986). Vitamin D2 Therapy of Pseudohypoparathyroidism: Assessment of Non-compliance. CLIN PEDIATR 25: 49-52 [Abstract]  
• Wasserman, R., Henion, J., Haussler, M., McCain, T. (1976). Calcinogenic factor in Solanum malacoxylon: evidence that it is 1,25-dihydroxyvitamin D3-glycoside. Science 194: 853-855 [Abstract]