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The prevalence of hypovitaminosis D and secondary hyperparathyroidism in obese Black Americans

Authors


  • Supported by ZO1 HD-00641 (to JAY) from the National Institute of Child Health and Human Development and by Y2-OD-2067 (to JAY) from the Office of Dietary Supplements, National Institutes of Health, DHHS.

Jack A. Yanovski, Unit on Growth and Obesity, DEB, NICHD, National Institutes of Health, Hatfield CRC, Room 1-3330, MSC 1103, Bethesda, MD 20892-1103. Tel: +301-496-0858; Fax: +301-402-0574; E-mail: jy15i@nih.gov

Summary

Context  Both obesity (body mass index, BMI ≥ 30 kg/m2) and Black race are associated with a higher risk of vitamin D deficiency and secondary hyperparathyroidism. We hypothesized the risk of hypovitaminosis D would therefore be extraordinarily high in obese Black adults.

Objective  To study the effects of race and adiposity on 25-hydroxyvitamin D [25(OH)D] and parathyroid hormone (iPTH).

Design, Setting and Participants  Cross-sectional study of 379 Black and White adults from the Washington D.C. area. BMI ranged from 19·9 to 58·2 kg/m2.

Main Outcome Measures  Prevalence of hypovitaminosis D [25(OH)D < 37·5 nmol/l] and secondary hyperparathyroidism [25(OH)D < 37·5 nmol/l with iPTH > 4·2 pmol/l].

Results  Obese Black subjects had lower mean 25(OH)D, 40·3 (SD, 20·3) nmol/l, compared with obese Whites, 64·5 (29·7), P < 0·001, nonobese Blacks, 53·3 (26·0), P = 0·0025 and nonobese Whites, 78·0 (33·5), P < 0·001. The prevalence of hypovitaminosis D increased with increasing BMI, and was greater (P < 0·001) in Blacks than Whites within all BMI categories examined. Among subjects with BMI ≥ 35 kg/m2, 59% of Blacks vs 18% of Whites had hypovitaminosis D (odds ratio 6·5, 95% confidence interval 3·0–14·2). iPTH was negatively correlated with 25(OH)D (r = 0·31, P < 0·0001), suggesting those with hypovitaminosis D had clinically important vitamin D deficiency with secondary hyperparathyroidism. For secondary hyperparathyroidism 35·2% of Blacks met the criteria, compared to 9·7% of Whites (OR 3·6, CI 1·5–98·8).

Conclusions  Obese Black Americans are at particularly high risk for vitamin D deficiency and secondary hyperparathyroidism. Physicians should consider routinely supplementing such patients with vitamin D or screening them for hypovitaminosis D.

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