Intestinal Calcium Absorption and Vitamin D Status in Chronic Cholestatic Liver Disease

Abstract

Metabolic bone disease is common in patients with cholestatic liver disease. The importance of vitamin D status and calcium malabsorption in the pathogenesis of bone disease in these patients remains undefined. We have measured intestinal calcium absorption in relation to vitamin D status in 14 patients with chronic cholestatic liver disease including 11 with primary biliary cirrhosis. Fractional calcium absorption was determined from radioactive counts in the right forearm after separate oral and intravenous doses of ⁴⁷CaCl₂ in the fasting state. Eight of 14 patients (57%) had a decreased calcium absorption compared to controls. A significant correlation was observed between serum 2 5-hydroxyvitamin D levels and fractional calcium absorption (r = 0.623, p < 0.02). Treatment with oral 2 5-hydroxyvitamin D₃ in three patients with low serum 2 5-hydroxyvitamin D levels resulted in correction of serum 2 5-hydroxyvitamin D levels and improvement in fractional calcium absorption. No correlation was found between serum 1,2 5-dihydroxyvitamin D levels and fractional calcium absorption (r = 0.221). Calcium malabsorption was common in this series of patients, and serum 25-hydroxyvitamin D levels were useful in predicting fractional calcium absorption. Treatment with oral 25-hydroxyvitamin D₃ was accompanied by improved calcium absorption.