Background: The effects of growth hormone (GH) on bone density in healthy adults is controversial. This study was performed to evaluate the effects of GH administration on bone density under controlled conditions in healthy adult rabbits.

Methods: Twenty healthy adult New Zealand white rabbits of both sexes were included in the study. The rabbits were divided into two groups. The experiment group received human GH and the controls placebo for three months. The density of femur and humerus were measured at proximal epiphysis, mid shaft and distal epiphysis by radiography, aluminum step-wedge and appropriate software. Measurements were performed in five stages, once before and four times after the administration of GH or placebo, with 3-week intervals.

Results: The mean concentration of serum insulin-like growth factor I (IGF-I) increased significantly after GH administration (P<0.05) in the experiment group. Bone density generally increased in all regions except the distal epiphysis of femur in the test group, but significant difference were only seen in the midshaft of femur in comparison to the controls (P<0.05). In the second stage, bone density decreased slightly in all regions except distal epiphysis of femur, but it increased in the next stages.

Conclusion: GH can increase bone density (mostly cortical bone) in adult rabbits. According to the similarities seen between growth hormone effects in rabbit and humans, this study suggests rabbits as a model for studying GH effects on bone density in acromegaly, growth hormone deficiency and even in healthy adult humans.