Human Parathyroid Hormone 1-34 Prevents Bone Loss in Experimental Biliary Cirrhosis in Rats

Background & Aims: Reduced bone mass and increased fracture rate are complications of primary biliary cirrhosis (PBC). The effect of intermittent administration of human parathyroid hormone (hPTH) 1-34 on bone mass and architecture in bile duct-ligated (BDL) rats was studied. Methods: Six-month-old male rats were subjected to BDL or sham operation (SO) and were treated from the second postoperative week intermittently with either hPTH 1-34 40 μg/kg per day, 80 μg/kg per day, or a vehicle for 4 weeks. Femoral and tibial bones were evaluated ex vivo by dual x-ray absorptiometry, microcomputed tomography, and histomorphometry. Serum osteocalcin and urinary deoxypyridinoline cross-links (DPD) were determined. Results: BDL rats had decreased bone mass compared with SO rats as indicated by a 6% decrease in femoral and tibial bone mineral density (BMD), 18% reduction in femoral trabecular bone volume (bone volume/total volume [BV/TV]), 17% decrease in trabecular thickness, and 10% decrease in tibial cortical thickness. The administration of hPTH 1-34 at 40 μg/kg per day increased femoral and tibial BMD (9% and 9%), femoral trabecular BV/TV (50%), trabecular thickness (50%), tibial cortical thickness (17%), and serum osteocalcin (82%). On the other hand, hPTH 1-34 80 μg/kg per day had no effect on BMD and tibial cortical thickness, was associated with a smaller increase in trabecular BV/TV (24%), and had a higher osteoclast number and DPD compared with untreated BDL rats and the lower hPTH 1-34 dose treatment group. Conclusions: BDL rats exhibit loss of bone mass and structure, which can be prevented by the intermittent administration of hPTH 1-34, a potential therapy for osteoporosis in PBC.