The development of the skeletal system occur during childhood. Thyroid hormones play an important role in the skeleton's maturation and maintenance of the structure and mass of bones. Juvenile hyperthyroidism affects bone metabolism. This study aimed to identify abnormalities in bone mineral density and the level of calciotropic hormones in juvenile hyperthyroidism to further improve the diagnosis of complications of juvenile hyperthyroidism. Materials and methods. The study was conducted by 21 health controls and 71 children and adolescents with juvenile hyperthyroidism. Anthropometric indicators were calculated using the WHO Anthro Plus personal computer software. Thyroid status and thyroid antibodies, osteocalcin, parathyroid hormone, vitamin D, calcium, phosphorus, alkaline phosphatase were determined using a closed-type immunochemistry analyzer Cobas e 411 Hitachi company Hoffman Le Roche (Switzerland) and its reagents. Bone mineral density was evaluated by dual-energy absorptiometry on a Stratos X-ray densitometer from Diagnostic Medical Systems, France. Results. In juvenile hypertrichosis, in comparison with the control, significantly low values of vitamin D and calcium in the blood serum were noted, the mean values of osteocalcin and alkaline phosphatase were substantially higher. There was no significant difference in the levels of parathyroid hormone and phosphorus in the blood serum in the compared groups. In 45.1% of patients, a decrease in bone mass was diagnosed compared to the age norm. A reliable direct correlation of vitamin D and calcium with bone density was revealed in all X-ray densitometry parameters and a reliable inverse correlation of osteocalcin, alkaline phosphatase and bone mineral density. Osteocalcin had a stronger inverse correlation with all dual-energy X-ray absorptiometry parameters and became a better biomarker than alkaline phosphatase. Conclusions. There is a decrease in bone mineral density in children with juvenile hyperthyroidism. Changes in the level of calciotropic hormones indicate a deranged bone metabolism. Serum osteocalcin can be used as a biomarker of bone metabolism in children with juvenile hyperthyroidism. It is recommended to assess the bones' condition during the initial examination of children with juvenile hyperthyroidism. The study was carried out following the principles of the Declaration of Helsinki. The study protocol was approved by the Local Ethics Committee of the participating institution. The informed consent of the parents of the children was obtained for the research. The author declares no conflicts of interest. Key words: juvenile hyperthyroidism, children, adolescents, bone mineral density; dual energy X-ray absorptiometry, osteocalcin, vitamin D.