Abstract

To study the effects of acute and chronic cholestasis on vitamin D metabolism we investigated six cases of acute extrahepatic obstructive jaundice and eight cases of primary biliary cirrhosis (PBC) (three supplemented with vitamin D). Plasma 25-hydroxyvitamin D (25OHD) was low in the patients with PBC unsupplemented with vitamin D but normal in obstructive jaundice. None of the patients with PBC showed radiological or histological evidence of osteomalacia. In PBC, dietary intake of vitamin D was low but response to ultra-violet irradiation of the skin was normal even in those with a considerably raised serum bilirubin. Patients with PBC or obstructive jaundice had low levels of 25 hydroxyvitamin D binding protein which correlated with the serum albumin. The half-life of intravenously injected ³H vitamin D₃ (³HD₃) and the subsequent production of ³H 25OHD were normal in all the patients with obstructive jaundice and in most with PBC. The two patients with PBC who produced less ³H 25OHD than expected were receiving vitamin D supplements. The urinary tritium (³H) excretion after the injection of ³HD₃ correlated with the serum bilirubin. After the injection of ³H 25OHD₃ the urinary excretion of ³H was minimal and did not correlate with the serum bilirubin, suggesting that the radioactivity appearing in the urine after the ³H vitamin D₃ injection was associated with vitamin D metabolites other than 25OHD. Factors contributing to the low plasma 25OHD in primary biliary cirrhosis may be a low dietary intake of vitamin D, inadequate exposure to ultra-violet light, and a tendency to urinary wastage of vitamin D metabolites.