Bone loss and reduced osteoblast function in primary biliary cirrhosis.

The association of bone loss with primary biliary cirrhosis is poorly understood. In 15 premenopausal female patients, only 2 of whom had fractures, mean bone mineral density was reduced at the lumbar spine but not at the midradius or distal radius. Bone loss was not statistically related to the duration or severity of liver disease. Urinary hydroxyproline excretion, an index for bone resorption, was not different from that of 15 age-matched normal women, but the serum concentration of bone Gla-protein (osteocalcin), a specific marker for bone turnover, was decreased (p less than 0.001). Bone histomorphometric examination in 13 patients showed no osteomalacia but a reduced bone formation rate despite normal values for fractional osteoblast-osteoid interface. The substantial early loss of trabecular bone is mediated by a severe reduction in osteoblast function, which may be caused by retained toxic substances associated with cholestasis.