24,25-Dihydroxyvitamin d3 and vitamin D status of community-dwelling black and white Americans.
BACKGROUND
24,25-Dihydroxyvitamin D [24,25(OH)2D] is a metabolite of 25-hydroxyvitamin D (25D). Blacks frequently have low total 25D without manifestations of vitamin D deficiency, suggesting that total serum 25D may incorrectly reflect vitamin D status in different racial groups. The ratio of serum 24,25(OH)2D to 25D [vitamin D metabolite ratio (VMR)] represents a new candidate biomarker for vitamin D status.


METHODS
We measured 24,25(OH)2D3 and 25D3 by mass spectrometry in a random community cohort of black (n = 212) and white (n = 164) Americans to evaluate VMR as a marker for vitamin D status. We measured parathyroid hormone concentrations by immunoassay to compare VMR and 25D3 against a physiological indicator of vitamin D deficiency.


RESULTS
Serum 24,25(OH)2D3 strongly correlated with 25D3 in both black and white study participants (r = 0.90, P < 0.001 and r = 0.86, P < 0.001 respectively). Blacks had lower mean 25D3 than whites [17.0 (7.8) vs 27.5 (11.3) ng/mL; 42.4 (19.5) vs 68.6 (28.2) nmol/L, P < 0.001] and lower mean 24,25(OH)2D3 [2.1 (1.3) vs 3.6 (2.0) ng/mL; 5.1 (3.1) vs 8.7 (4.8) nmol/L, P < 0.001]. In contrast to total 25D3 concentrations, mean VMR values were similar in blacks and whites [11.9 (4.0) vs 12.5 (3.4), P = 0.16, respectively] and were negatively correlated with parathyroid hormone concentrations in both races (rs = -0.26, P < 0.001, and rs = -0.25, P < 0.001, respectively).


CONCLUSIONS
Our results provide further evidence that measurement of total 25D for assessment of vitamin D status in patients of African descent deserves reevaluation and suggest that alternative measures such as VMR should be considered.
Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA; ahberg@bidmc.harvard.edu rthadhani@mgh.harvard.edu.
Anders H
AH
Berg
Division of Endocrinology, Massachusetts General Hospital, Boston, MA;
Camille E
CE
Powe
Laboratory of Epidemiology and Population Sciences, National Institute on Aging, National Institutes of Health, Baltimore MD;
Michele K
MK
Evans
Division of Nephrology, Massachusetts General Hospital, Boston, MA;
Julia
J
Wenger
Division of Nephrology, Massachusetts General Hospital, Boston, MA;
Guillermo
G
Ortiz
Laboratory of Epidemiology and Population Sciences, National Institute on Aging, National Institutes of Health, Baltimore MD;
Alan B
AB
Zonderman
Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA;
Pirianthini
P
Suntharalingam
Division of Nephrology, Massachusetts General Hospital, Boston, MA;
Kathryn
K
Lucchesi
Department of Medicine, San Francisco General Hospital and University of California, San Francisco, CA;
Neil R
NR
Powe
Division of Nephrology, Beth Israel Deaconess Medical Center, Boston, MA; Howard Hughes Medical Institute, Chevy Chase, MD.
S Ananth
SA
Karumanchi
Division of Nephrology, Massachusetts General Hospital, Boston, MA; ahberg@bidmc.harvard.edu rthadhani@mgh.harvard.edu.
Ravi I
RI
Thadhani
D015650:24,25-Dihydroxyvitamin D 3 / Q000097:blood*; D000328:Adult; D001741:Black or African American; D015415:Biomarkers / Q000097:blood; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood; D015203:Reproducibility of Results; D053719:Tandem Mass Spectrometry / Q000379:methods; D014807:Vitamin D / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood; D044465:White People
D015415:Biomarkers; D010281:Parathyroid Hormone; D014807:Vitamin D; D015650:24,25-Dihydroxyvitamin D 3