Low serum 25-hydroxyvitamin D in hereditary hemochromatosis: relation to iron status. Chow LH , Frei JV , Hodsman AB , Valberg LS . Abstract Under normal conditions, vitamin D absorbed from the diet or synthesized in the skin is transported to the liver where it undergoes hydroxylation . The purpose of this study was to determine whether excess hepatic iron affects this process and the subsequent production of 1,25-dihydroxyvitamin D (1,25-[OH]2D) in the kidney. Mean serum 25-hydroxyvitamin D (25-OHD) concentrations in untreated hereditary hemochromatosis were 13 +/- 6 (SD) in 9 patients with cirrhosis, 13 +/- 6 in 5 patients with hepatic fibrosis, and 22 +/- 6 in 10 patients with normal hepatic architecture aside from siderosis and were significantly lower than the levels found in 24 controls matched for age, sex, and season, p less than 0.05. The mean serum 25-OHD levels in the two groups with hemochromatosis and hepatic damage were significantly lower than the...