Dose response of growth hormone on fracture healing in the rat.

The effect of different doses of biosynthetic human growth hormone on the mechanical properties of tibial fractures and intact bones was studied in a rat model; a three-point bending test was applied 40 days after fracturing. Ninety-day-old female rats received a daily dose of 0, 0.08, 0.4, 2.0, or 10 mg of growth hormone/kg body weight starting 1 week before fracture and continuing until mechanical testing. In the animals given 2.0 and 10 mg of hormone, the ultimate load sustained by the fractures, stiffness, and energy absorption at ultimate load increased, while the ultimate stress increased only in the latter groups. In the intact bones, ultimate load of the bones increased in the same groups, while stiffness and energy absorption at ultimate load increased only in the group given the highest dose of hormone.