The effect of local injection of the human growth hormone on the mandibular condyle growth in rabbit

BACKGROUND: The aim of this study was to evaluate the effect of local injection of human growth hormone (GH) in stimulating cartilage and bone formation in a rabbit model of temporomandibular joint (TMJ). MATERIALS AND METHODS: In an experimental animal study, 16 male Albino New Zealand white rabbits aged 12 weeks were divided into two groups: In the first group (7 rabbits) 2 mg/kg/1 ml human GH and in the control group (9 rabbits) 1 ml normal saline was administered locally in both mandibular condyles. Injections were employed under sedation and by single experienced person. Injections were made for 6 times with 3 injections a week in the all test and control samples. Rabbits were sacrified at the 20th day from the beginning of study and TMJs were histologically examined. ANOVA (two-sided) with Dunnett post hoc test was used to compare data of bone and cartridge thickness while chi-square test was used to analyze hyperplasia and disk deformity data. P < 0.05 was considered as significant. RESULTS: Cartilage layer thickness was greater in the GH-treated (0.413 ± 0.132) than the control group (0.287 ± 0.098) (P value = 0.02). Although bone thickness and condylar cartilage hyperplasia were greater in the GH-treated group, these differences were not statistically significant (P value = 0.189 and 0.083, respectively). There was no statistically significant difference between two groups regarding the disc deformity (P value = 0.46). CONCLUSION: Local injection of human GH in the TMJ is able to accelerate growth activity of condylar cartilage in rabbit.