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

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). In an experimental animal study, 16 male Albino New Zealand white rabbits aged 12 weeks were divided into two groups: In the fi rst 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 sacrifi ed 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 signifi cant. 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 signifi cant (P value = 0.189 and 0.083, respectively). There was no statistically signifi cant difference between two groups regarding the disc deformity (P value = 0.46). Local injection of human GH in the TMJ is able to accelerate growth activity of condylar cartilage in rabbit.