Berg, AndersBhan, IshirPowe, CamilleKarumanchi, SubbianXu, DihuaThadhani, Ravi2018-01-182017Berg, Anders H., Ishir Bhan, Camille Powe, S. Ananth Karumanchi, Dihua Xu, and Ravi I. Thadhani. 2017. “Acute Homeostatic Changes Following Vitamin D2 Supplementation.” Journal of the Endocrine Society 1 (9): 1135-1149. doi:10.1210/js.2017-00244. http://dx.doi.org/10.1210/js.2017-00244.http://nrs.harvard.edu/urn-3:HUL.InstRepos:34651927Context: Changes in vitamin D binding protein (DBP) concentrations and catabolism of 25-hydroxyvitamin D to 24,25-dihydroxyvitamin D (24,25D) after vitamin D2 supplementation may alter concentrations and bioavailability of circulating 25-hydroxyvitamin D (25D). Objective: Examine acute changes in vitamin D metabolism and bioavailability after vitamin D2 supplementation. Methods: Study design was secondary analysis of a single-arm interventional study. Thirty consenting volunteers were treated with five 50,000 IU oral doses of ergocalciferol over 2 weeks. Main outcome measures included concentrations of DBP, vitamin D metabolites, and bioavailable 25-hydroxyvitamin D (25D) in pre- and posttreatment serum samples. Results: After supplementation, 25D2 (mean ± standard deviation) increased from 1.4 ± 0.9 ng/mL to 45.3 ± 16.5 ng/mL (P < 0.0001), and 25D3 levels decreased from 26.8 ± 9.9 ng/mL to 19.7 ± 8.2 ng/mL (P < 0.0001). Total 25D (25D2 plus 25D3) increased from 28.2 ± 10.0 ng/mL to 65.0 ± 21.1 ng/mL (152.2% ± 102.5%; P < 0.0001). DBP and total 24,25D concentrations increased 39.1% ± 39.4% (165.6 ± 53.8 µg/mL to 222.0 ± 61.1 µg/mL; P < 0.0001) and 31.3% ± 48.9% (3.9 ± 2.0 ng/mL to 4.7 ± 2.1 ng/mL; P = 0.0147), respectively. In contrast to total 25D, bioavailable 25D increased by 104.4% ± 99.6% (from 5.0 ± 2.0 ng/mL to 8.7 ± 2.7 ng/mL; P < 0.001), and 1,25D increased by 32.3% ± 38.8% (from 45.5 ± 10.7 pg/mL to 58.1 ± 13.0 pg/mL; P = 0.0006). There were no changes in calcium or parathyroid hormone (P > 0.05 for both). Conclusion: Changes after vitamin D2 supplementation involve acute rise in serum DBP and 24,25D, both of which may attenuate the rise in bioavailable 25D and 1,25D.en-USParathyroid, Bone, and Mineral Metabolism24,25-dihydroxyvitamin D25-hydroxvitamin Dergocalciferol supplementationfeedback regulationvitamin D binding proteinJournal Article2018-01-1810.1210/js.2017-00244