Differentiated thyroid carcinoma (DTC) is usually treated by surgery followed by radioactive Iodine intake.Subclinical hyperthyroidism is often present in patients treated with TSH-suppressive doses of Levo-thyroxine (Eltroxine) for thyroid nodular disease or as post-operative treatment for differentiated thyroid carcinoma to prevent local and/or metastatic progressionWe conducted a study on 50 patients with surgically treated DTC followed by radioactive iodine ablation and receiving suppressive Eltroxine therapy referred to the center of clinical oncology & nuclear medicine (NEMROCK). Another 10 healthy individuals were taken as a control group. Measurement of thyroid related hormones (Free T3, Free T4 & TSH). Gated Equilibrium Radionuclide Angiography (ERNA) study was done for all patients and controls. The results showed that long-term suppressive Eltroxine therapy in patients with DTC affects the cardiac function.