Evaluation of increased serum ferritin levels in patients with hyperthyroidism

To further elucidate the mechanism of increased serum ferritin levels in hyperthyroidism, the changes in erythrocytes and serum iron and total iron-binding capacity levels were examined in addition to serum ferritin levels in 13 hyperthyroid patients. The mean values of hemoglobin, red blood cells, and packed cell volume were increased by antithyroid therapy. While the serum levels of iron did not change, those of total iron-binding capacity increased significantly after achieving a euthyroid state. Increased serum ferritin levels returned to normal through antithyroid therapy. Furthermore, the serum ferritin levels of four anemic patients were significantly higher than those of nine nonanemic patients. Thus it is concluded that the increase in serum ferritin levels in patients with hyperthyroidism may be due to the direct action of thyroid hormones on its synthesis, while in some cases complicated with anemia impaired iron utilization by erythropoietic cells may also be involved.