Purpose: The study was conducted to evaluate the effect of salmon calcitonin (sCT) on fracture healing in normal and hypogonadal male rats.

Material and Method: Fifty six male Wistar rats, aged 3 months, were undertaken hemiosteotomy of the distal femur shaft, of standard length and width. Half of the animals had been orchiectomised at the age of 2 months. The animals were divided in 8 groups, 7 rats each, as follow: A, a (normal, no sCT), B, b (normal+Sct), C,c(orchiectomised) and D,d (orchiectomised+Sct). Salmon calcitonin was administered immediately after the hemiosteotomy in a dose of 5IU/day subcutaneously. Groups A, a, C and c were given placebo. The animals of the groups a b, c, and d were killed at 2 weeks, while the animals of the groups A, B, C, and D were killed at 4 weeks. After the euthanasia, total bone density and cortical bone density of the callus was estimated by peripheral quantitative computed tomography (pQCT). Histological and histomorfometric parameters of the callus were estimated as well.

Results: The mean cortical bone density was 1221.93±13.82 (g/cm³±SE) for the group a, 1281.3±13.57 for b, 1221.41±18.24 for c, 1245±17.12 for d, 1173.45±34.14 for A, 1298.9±11 for B, 1280.78±13.68 for C, and 1279.4U19.2 for D. The mean total bone density was 843.95±13.69 (g/cm³±SE) for the group a, 859.84±26.46 for b, 892.27±25.3 fore, 861.37±10.88 for d, 818.97±32.5 for A, 926.39±19.6 for B, 888.31±24.19 for C, and 912.75±28.13 for D. Values of cortical bone density in group b and B were significantly greater than a and A, respectively (b> a, p=0.01 and B> A, p=0.002). Total bone density of the callus was statistically greater in group B than A (B> A, p=0.01). According to the histological and histomorphometric results, sCT increased the amount of cartilage (p=0.014) and the amount of woven bone (p=0.015) in group b compared to a, while osteoblasts number showed no difference between the two groups. Comparing groups c and d, sCT increased the amount of cartilage (p=0.036) and the amount of woven bone (p=0.0014) in group d compared to c, while decreased osteoblasts number in group d (p=0.03). In four weeks the amount of cartilage is significant greater in group D versus C (p=0.006), as well as the amount of woven bone (p=0.0004). The size of the callus is significant greater in group D compared to C as well (p=0.052).

Conclusion: It appears that salmon calcitonin administration improves significantly the parameters of callus bone density in normal rats and increases the amount of cartilaginous callus and woven bone both in normal and orchiectomised rats.