25-HYDROXYVITAMIN-D-3 REVERSES ALTERATION OF THE VITAMIN-D-ENDOCRINE SYSTEM IN BLACKS

BACKGROUND: Previous findings indicated that serum 25-hydroxyvitamin D and urinary calcium are decreased and serum immunoreactive parathyroid hormone, serum 1,25-dihydroxyvitamin D, and urinary cyclic adenosine 3',5'-monophosphate are increased in normal black compared to normal white subjects. Studies were carried out to determine if alteration of the vitamin D-endocrine system in blacks is reversed by oral supplementation with 25-hydroxyvitamin D-3. PATIENTS AND METHODS: Eight normal young adult black men and women were admitted two times to a metabolic ward for 2.5 days and studied after no treatment and again after treatment for 1 week with oral 25-hydroxyvitamin D-3, 40 to 60 mu g/d. Six of the subjects underwent a postcontrol study after discontinuation of treatment. RESULTS: 25-Hydroxyvitamin D-3 treatment significantly increased serum 25-hydroxyvitamin D and urinary calcium and reduced serum 1,25-dihydroxyvitamin D and urinary cyclic adenosine 3',5'-monophosphate, an index of function of parathyroid hormone. In a postcontrol study, values for serum 25-hydroxyvitamin D, serum 1,25-dihydroxyvitamin D, and urinary calcium had returned to control values. CONCLUSIONS: The results provide evidence that reduction of serum 25-hydroxyvitamin D contributes to or accounts for alteration of the vitamin D-endocrine system in black subjects.