ABSTRACT
BACKGROUND:Overproduction of thyroid hormones is shown to increase the activities of osteoblasts and osteoclasts, stimulating bone resorption and transformation. Inadequate compensation of increased bone resorption by bone transformation results in an increased loss of bone mass. OBJECTIVE:To investigate the effects of hyperthyroidism on the density of the alveolar bone. METHODS:Twenty-four New Zealand rabbits were equal y randomized into hyperthyroidism group and control group. Rabbits in the hyperthyroidism group or control group were daily injected intraperitoneal y with 50μg/kg levothyrocine diluted in physiological saline solution or equal volume of physiological saline. At 8 weeks after treatment, serum levels of thyroid hormones (FT3 and FT4), alkaline phosphatase, magnesium and calcium, phosphorus were determined;meanwhile, the bone densities of the lumbar vertebra, mandible, bilateral distal femur were determined by dual energy X-ray absorptiometry and the correlation analysis was performed. RESULTS AND CONCLUSION:At 8 weeks after treatment, serum levels of FT3, FT4, alkaline phosphatase calcium, phosphorus, and magnesium in the hyperthyroidism group were significantly increased (P<0.01), while the bone densities of the lumbar vertebra, mandible, bilateral distal femur were significantly decreased (P<0.05), compared with the control group. Bone density of the mandible was positively correlated with the bone density the lumbar vertebra and bilateral distal femur. These findings suggest that the changes in FT3 and FT4 are sufficient for the diagnosis of hyperthyroidism. Hyperthyroidism results in the decreased density of the alveolar bone, indicating the occurrence of osteoporosis.