NEW YORK (Reuters Health) - Renal transplant patients are at risk of deficiency in 25-hydroxyvitamin D3 (25(OH)D), a new study shows, because of lack of sun exposure.

Because they are on immunosuppression, kidney transplant patients must protect themselves from sun exposure, Dr. Kerstin Querings of the Universtatsklinikum des Saarlandes in Homburg/Saar, Germany, and colleagues note in the February issue of the Journal of Clinical Endocrinology & Metabolism.

Serum levels of the active vitamin D metabolite 1,25-dihydroxyvitamin D3 are frequently monitored in patients with bone disease after renal transplant, the researchers add, but levels of this metabolite can be normal in patients with vitamin D deficiency. Less is known about 25(OH)D in patients after renal transplant, they add, and low levels of this metabolite -- the major circulating form of vitamin D -- can affect the body's ability to produce 1,25-dihydroxyvitamin D3.

To determine whether renal transplant patients might be deficient in 25(OH)D, the researchers compared 31 renal transplant patients and 31 age- and gender-matched controls at the end of winter.

Average serum 25(OH)D levels were 10.9 ng/mL for the renal transplant patients, compared to 20.0 ng/mL for the controls. Ten of the kidney transplant patients had undetectable 25(OH)D levels, while another five had levels below 15 ng/mL.

Dr. Querings and her team recommend a single 50,000 IU dose of vitamin D once weekly for eight weeks for patients with vitamin D deficiency, and 50,000 IU once or twice a month to maintain levels of the vitamin. Optimal levels of 25(OH)D are above 20 ng/mL.

"If we follow the guidelines discussed above carefully, these measures will protect renal transplant recipients sufficiently against the serious health problems of vitamin D deficiency without increasing their risk to develop UV-induced skin cancer," the researchers conclude.

J Clin Endocrinol Metab 2006;91:526-529

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