Growth hormone promotes healing of tibial fractures in the rat

The effect of administering growth hormone for different periods of time on the mechanical properties of healing rat tibial fractures was investigated after 40 days of healing. Biosynthetic human growth hormone, 2.7 mg/kg body weight/day, was administered to three groups of rats for 1, 2, or 3 weeks following fracture, whereas isotonic saline was administered to a control group for 3 weeks. The ultimate load values and maximum stiffness of the fractures increased in the groups injected with growth hormone for 2 or 3 weeks; linear regression analysis revealed a high probability of a positive linear relationship. In the intact bones an increase in ultimate load, maximum stiffness, and energy absorption at ultimate load was found in the group injected with growth hormone for 3 weeks, with linear regression analysis again showing a high probability of a positive linear relationship.