1. ¹Department of Medicine, Renal Unit, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
2. ²Division of Nephrology, Department of Medicine, University of Washington School of Medicine, Seattle, Washington, USA
3. ³Department of Nephrology, University of British Columbia, Vancouver, British Columbia, Canada

Correspondence: OM Gutiérrez, Department of Medicine, Renal Unit, Massachusetts General Hospital, Harvard Medical School, Gray/Bigelow 100355 Fruit Street, Boston, Massachusetts 02114, USA. E-mail: ogutierrez@partners.org

Received 31 July 2007; Revised 28 September 2007; Accepted 6 November 2007; Published online 6 February 2008.

Abstract

Disorders of mineral metabolism develop early in chronic kidney disease, but it appears that Blacks with stage-5 disease have more severe secondary hyperparathyroidism than other races. We measured levels of parathyroid hormone, calcium, phosphorus, 25-hydroxyvitamin D (25D) and 1,25-dihydroxyvitamin D (1,25D) in 227 Black and 1633 non-Black participants in the SEEK study, a multi-center cohort of patients with early chronic kidney disease. Overall, Blacks had similar 1,25D levels compared with non-Blacks, but significantly lower levels of 25D with higher levels of calcium, phosphorus, and parathyroid hormone, and were significantly more likely to have hyperphosphatemia than non-Blacks. In multivariable analyses adjusted for age, gender, estimated glomerular filtration rate, body mass index, and diabetes, Blacks had significantly lower 25D and higher parathyroid hormone levels than non-Blacks, with the latter parameter remaining significant after further adjustment for calcium, phosphorus, 25D, and 1,25D. The association between Black race and secondary hyperparathyroidism, independent of known risk factors, suggests that novel mechanisms contribute to secondary hyperparathyroidism in Blacks with chronic kidney disease.