Evidence for 25-hydroxyvitamin D deficiency as a factor contributing to osteopenia in diabetic patients with idiopathic haemochromatosis

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Abstract
Osteopenia is frequently encountered in the course of idiopathic hemochromatosis. To establish the mechanism of this bone disorder, the following parameters were studied in 9 diabetic patients with idiopathic hemochromatosis: the intestinal Ca absorption measured by a double radiotracer technique; the bone mineral content (BMC, mg/cm2) determined on the forearm by the Cameron''s absorptiometric technique; and the plasma 25-hydroxyvitamin D (25-OH-D ng/ml) by a competitive protein-binding radioassay. The results were compared to those obtained in 10 controls and in 8 diabetics without hemochromatosis. The patients suffering from hemochromatosis had a significant fall in total fractional absorption of Ca and BMC as compared with controls and diabetics without hemochromatosis. Plasma 25-OH-D was significantly lower in hemochromatosis patients (5.1 .+-. 0.6 ng/ml) than in controls (16.4 .+-. 1.3 ng/ml, P < 0.01) and in diabetics without hemochromatosis (14.2 .+-. 1.4 ng/ml, P < 0.02). Hemochromatosis patients exhibit important disturbances in Ca homeostasis, i.e., low concentration of plasma 25-OH-D and reduced intestinal absorption of Ca. The latter abnormalities may be related to the bone rarefaction observed in these patients.