Mineral and endocrine metabolism during fracture healing in dogs

The blood levels of parathormone (PTH), calcitonin (CT), vitamin D metabolites, calcium, phosphate, magnesium and alkaline phosphatase (AKP) were determined in 13 young dogs with experimental fractures of long bones. The parameters were measured before the fracture and during healing until the appearance of an early callus. Serum Ca levels were significantly reduced immediately after the fracture (10.95 ± 0.30 mg/dl to 10/25 ± 0.25 mg/dl; p<0.05). Significant rises in serum levels of PTH (0.99 ± 0.10 ng/ml to 1.57 ± 0.22 ng/ml; p<0.01); CT (0.14 ± 0.01 ng/ml to 0.18 ± 0.01 ng/ml; p<0.05; 24,25-dihydroxyvitamin D (13 ± 2 ng/ml to 19 ± 3 ng/ml; p<0.01) and AKP (153 ± 24 U/l to 211 ± 26 U/l; p<0.01) were noted during fracture repair. A reduction in serum levels of 25-hydroxyvitamin D (22 ± 2 ng/ml to 15 ± 1 ng/ml; p<0.001) was noted at the same time. The parameters returned or tended to return to normal levels during callus development. The data demonstrate the changes in levels of Ca-regulating hormones in response to bone injury. This suggests that CT and 24,25-dihydroxyvitamin D (24,25-(OH)₂-D) can be associated with the process of callus formation.