What are the clinical characteristics of type T3 hyperthyroidism?

Type T3 hyperthyroidism occurs in patients with diffuse, nodular, or mixed goiter at early, treatment, or relapse stages. The clinical manifestations are similar to those of the usual type, but generally milder. It is characterized by elevated serum total T3 and free T3, and normal or low total T4 and free T4. Thyroid iodine uptake rate is normal or high, but not inhibited by exogenous T3. The cause of the disease may be hyperthyroidism when iodine deficiency occurs or T3 increases more rapidly in the course of disease, but T4 decreases more rapidly during treatment. Its characteristics are normal T3 and T4 in blood and significant decrease in thyrotropin.