Higher 25(OH)D2 is associated with lower 25(OH)D3 and 1,25(OH)2D3.
BACKGROUND
Despite common use of supplemental vitamin D2 in clinical practice, the associations of serum vitamin D2 concentrations with other vitamin D metabolites and total vitamin D are unclear.


OBJECTIVE
The aim of the study was to measure vitamin D2 and D3 levels and examine their associations with each other and with total vitamin D.


METHODS
We performed a cross-sectional analysis of 679 randomly selected participants from the Osteoporotic Fractures in Men Study. 25-Hydroxyvitamin D2 [25(OH)D2], 25(OH)D3, 1,25-dihydroxyvitamin D2 [1,25(OH)2D2], and 1,25(OH)2D3 were measured using liquid chromatography-tandem mass spectrometry and were summed to obtain total 25(OH)D and 1,25(OH)2D. Associations between all metabolites (D2, D3, and total levels) were examined using Wilcoxon rank-sum tests and Spearman correlations.


RESULTS
25(OH)D2 and 1,25(OH)2D2 were detectable in 189 (27.8%) and 178 (26.2%) of the men, respectively. Higher 25(OH)D2 levels did not correlate with higher total 25(OH)D (r = 0.10; P = .17), although median total 25(OH)D was slightly higher in those with detectable vs undetectable 25(OH)D2 (25.8 vs 24.3 ng/mL; P < .001). 25(OH)D2 was not positively associated with total 1,25(OH)2D levels (r = -0.11; P = .13), and median 1,25(OH)2D level was not higher in those with detectable vs undetectable 25(OH)D2. Higher 25(OH)D2 was associated with lower 25(OH)D3 (r = -0.35; P < .001) and 1,25(OH)2D3 (r = -0.32; P < .001), with median levels of both D3 metabolites 18-35% higher when D2 metabolites were undetectable.


CONCLUSIONS
In a cohort of older men, 25(OH)D2 is associated with lower levels of 25(OH)D3 and 1,25(OH)2D3, suggesting that vitamin D2 may decrease the availability of D3 and may not increase calcitriol levels.
Division of Endocrinology (C.M.S., C.G.L., E.S.O.), Bone and Mineral Unit (C.M.S., C.M.N., S.S., C.G.L., E.S.O.), and Department of Public Health and Preventive Medicine (C.M.N.), Oregon Health & Science University, Portland, Oregon 97239; Research Service (C.G.L.), Portland Veterans Affairs Medical Center, Portland, Oregon 97239; Division of Epidemiology (E.B.-C.), Department of Family & Preventive Medicine, University California San Diego, La Jolla, California 92093-0607; Laboratory of Diagnostic Medicine (I.J., D.V.), KU Leuven, University of Leuven, 3000 Leuven, Belgium; Department of Epidemiology (J.A.C.), Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania 15261; and Division of Geriatric Medicine and Centre for Metabolic Bone Diseases (S.B.), and Laboratory of Clinical and Experimental Endocrinology (R.B., D.V.), KU Leuven, University of Leuven, 3000 Leuven, Belgium.
Christine M
CM
Swanson
Carrie M
CM
Nielson
Smriti
S
Shrestha
Christine G
CG
Lee
Elizabeth
E
Barrett-Connor
Ivo
I
Jans
Jane A
JA
Cauley
Steven
S
Boonen
Roger
R
Bouillon
Dirk
D
Vanderschueren
Eric S
ES
Orwoll
D015652:25-Hydroxyvitamin D 2 / Q000097:blood*; D000368:Aged; D000369:Aged, 80 and over; D001774:Blood Chemical Analysis / Q000379:methods; D002112:Calcifediol / Q000097:blood*; D002117:Calcitriol / Q000097:blood*; D002853:Chromatography, Liquid; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D006801:Humans; D008297:Male; D058866:Osteoporotic Fractures / Q000097:blood* / Q000453:epidemiology; D053719:Tandem Mass Spectrometry
D015652:25-Hydroxyvitamin D 2; D002117:Calcitriol; D002112:Calcifediol