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.