Levels of bioavailable, and free forms of 25(OH)D after supplementation with vitamin D3 in primary hyperparathyroidism

Abstract

25 hydroxyvitamin D [25(OH)D] is the major metabolite for ascertaining vitamin D status, which circulates bound to a speci c carrier (vitamin D-binding protein -VDBP). A portion that circulates unbound vary according to the VDBP genotype. This study evaluates the behavior of different forms of 25(OH)D, before and after supplementation with 14,000 IU of vitamin D3, weekly for 12 weeks, in individuals with primary hyperparathyroidism and controls. Fifty-six patients with active primary hyperparathyroidism (PHPT) and 64 paired controls (CTRL), not taking vitamin D3 for the last three months, were enrolled. The genetic isotypes of VDBP were determined to calculate bioavailable and free 25(OH)D. A p<0.05 was considered signi cant.There were no statistical differences in free, bioavailable, and total 25(OH)D levels between PHPT and CTRL groups at baseline. The distribution of VDBP haplotypes 1s/1s, 1f/1f, 1s/1f, 2/2, 1s/2, and 1f/2 was similar between groups. After supplementation, all three forms of 25(OH)D proportionally increased within each group, although the percentage increment was lower in the PHPT group (p<0.05).Total 25(OH)D is better correlated with PTH in the PHPT group than bioavailable and free 25(OH)D (r=-0.41; p<0.05).The concentrations of total, free, and bioavailable 25(OH)D were similar in both PHPT and CTRL groups, and all forms increased proportionally after supplementation, although this increment percentage was higher in the CTRL group, with a subsequent reduction of PTH and AP. Total 25(OH)D correlated better with PTH than other forms, suggesting no advantages in measuring free or bioavailable 25(OH)D in these situations.

The effects of vitamin D on all-cause mortality in different diseases: an evidence-map and umbrella review of 116 randomized controlled trials

“…The pathological heterogeneity results in different recommended doses for different diseases. For respiratory infections, a daily supplementation of 400–1,000 IU is most effective ( 161 ), and osteoporosis patients are advised to take 800 IU/day ( 162 ), while primary hyperparathyroidism requires a higher dose of 2,800 IU/day due to the low serum calcium trait of PTH ( 163 ). Therefore, a universal agreement has been reached that the key to supplementing vitamin D is achieving optimal serum 25(OH)D levels, rather than chasing the best supplementary dose.…”