Serum Vitamin D Metabolites Are not Responsible for Low Turnover Osteoporosis in Chronic Liver Disease

We measured the concentrations of vitamin Dbinding protein (DBP), total 25-hydroxyvitamin D, total 1, 25-dihydroxyvitamin D [1, 25-(OH)₂D], and free 1, 25-(OH)₂D in sera of 107 patients with histologically proven chronic liver disease. Bone density measurements and dynamic skeletal histomorphometry were also performed. Osteoporosis, as defined by arbitrary criteria, was found in 42 patients (39%), while no patient had osteomalacia. Serum concentrations of vitamin Dbinding protein, 25-hydroxyvitamin D, total 1, 25-(OH)₂D, and free 1, 25-(OH)₂D were reduced in patients with cirrhosis, but not in the noncirrhotic patients. Bone formation rates, which were low in 55 patients (51%), were correlated with liver functions, but not with the concentrations of either vitamin D metabolite.A subgroup of 44 patients with low serum 1, 25-(OH)₂D concentrations and low bone formation rates failed to show an appropriate increase in serum bone Gla protein after 1, 25-(OH)₂D₃ administration even though serum concentrations of 1, 25-(OH)₂D rose normally. These data suggest that the bone disease in patients with hepatic disorders is not related to the serum concentrations of vitamin D metabolites or the effect of these metabolites on osteoblast function.