The effects of vitamin D, 2.5 mg (100,000 U)/d for 4 d, on serum calcium, serum 25-hydroxyvitamin D (25-OHD) and serum 1a,25-dihydroxyvitamin D (1a,25(OH)2D) were compared in 24 normal adults and 12 normal children. The daily dose of vitamin D was 1,500 U/kg body wt in children weighing <45 kg. Vitamin D increased mean serum calcium from 9.5±0.1 to 9.8±0.1 mg/dl (P < 0.05), increased mean serum phosphorus from 4.6±0.1 to 5.0±0.1 mg/dl (P < 0.01), increased mean serum 25-OHD from 25±3 to 34±4 ng/ml (P < 0.001), and increased mean serum 1a,25(OH)2D from 34±3 to 42±4 pg/ml (P < 0.02) in children. In contrast, vitamin D increased mean serum 25-OHD from 18±2 to 39±6 ng/ml (P < 0.001) and did not change mean serum calcium (9.4±0.1 vs. 9.5±0.1 mg/dl), mean serum phosphorus (4.0±0.1 vs. 4.1±0.1 mg/dl), or mean serum 1a,25(OH)2D (31±2 vs. 29±3 pg/ml) in adults. Mean serum 1a,25(OH)2D was significantly higher after vitamin D in children than in adults (P < 0.02). These results provide evidence that circulating 1a,25(OH)2D is not as tightly regulated in children as it is in adults. This difference in regulation could account in part for the higher values for serum 1a,25(OH)2D observed in children.
Stern, Paula H.; Taylor, Ashby B.; Bell, Norman H.; and Epstein, Sol, "Demonstration That Circulating 1α,25-Dihydroxyvitamin D is Loosely Regulated in Normal Children" (1981). MUSC Faculty Journal Articles. 9.