-thalassemia is a widely prevalent inherited blood disorder that results in disrupted iron metabolism due to iron accumulation, while also influencing calcium metabolism and exacerbating clinical outcomes. The research included analyses from 30 children aged 6-11 years who had regularly received blood transfusions from 2019 to 2023, with a control group of 15 healthy children of similar age. Alongside the general blood analysis parameters, the study measured the levels of iron, ferritin, calcium, phosphorus, vitamin D, ferroportin, hepcidin, and fibroblast growth factor-23 (FGF-23) in the blood serum, comparing these with the control group. The study revealed that, in patients with major beta-thalassemia, the accumulation of iron and ferritin in the blood serum was associated with a decrease in hepcidin (p<0.001), while a deficiency in vitamin D (p<0.001) led to an increase in FGF-23 levels (p<0.05). The correlation analysis between the studied markers showed that an increase in FGF-23 levels in the blood serum not only affects calcium-phosphorus metabolism but also iron metabolism. The findings obtained may be significant for the diagnosis and treatment planning of major -thalassemia in the future.