Thyroid hormones exert influence on various systems including growth and development, body hemodynamics, basal metabolism, body temperature, digestive system, nervous system, and skeletal system1. Thyroid diseases fundamentally arise from excessive or insufficient hormone production. Thyroid hormones play a crucial role in skeletal development, growth, and the regulation of bone metabolism2,3.

Hyperthyroidism is increased hormone synthesis and excess thyroid hormone from the thyroid gland3,4. In hyperthyroidism, acceleration of bone remodeling, decrease in bone density, osteoporosis, and increase in fracture frequency have been observed. Cortical porosity increases, cortical thickness and bone mineral density (BMD) decrease5. Increased frequency of caries in thyrotoxicosis, xerostomia, premature eruption of teeth and extensive osteoporosis of the jaws can be seen3,6.

Studies conducted on patients with hypothyroidism reveal an increase in bone density; however, the risk of fractures is elevated due to poor bone quality. Replacement therapy with levothyroxine sodium in hypothyroid patients may result in a decrease in BMD following treatment initiation7. Dental manifestations include delayed eruption, macroglossia, short roots, and thinning of the lamina dura. Additionally, the maxilla is relatively smaller compared to the mandible8.

Prior investigations have assessed the BMD in the spine, femur, and humerus of individuals with hypothyroidism and hyperthyroidism using dual-energy X-ray absorptiometry (DEXA), revealing a significant decrease in BMD9,10,11,12. It is known that in thyroid hormone disorders and thyrotoxicosis in adults cause osteoporosis and reduce BMD13.

Fractal analysis provides a quantitative measure of the intricate microarchitecture complexity of trabecular bone. By manipulating the grayscale tones in radiographic images, the bone trabeculae are processed to facilitate fractal analysis, wherein white colors and spaces are represented as black colors, enhancing the visualization of trabecular patterns. Previous studies have demonstrated a decrease in fractal dimension (FD) analysis in disease conditions associated with reduced bone mineralization14,15,16. Consequently, it has been established that the fractal analysis method is a suitable approach for diagnosing osteoporosis in the jaws14,17,18.

As far as we know, there is no study in the literature that evaluates the jaw bone structure in hyperthyroidism and hypothyroidism patients using the fractal analysis method. The aim of this study was to evaluate the trabecular and cortical bone structure of the mandible of patients with hyperthyroidism and hypothyroidism and to compare it with a healthy control group without any systemic disease.