| Graves' disease | Diffuse thyroid gland enlargement; hypermetabolism; elevated free T4 level, low TSH level, elevated thyroid autoantibody level; increased radioactive iodine uptake |
| Subacute granulomatous thyroiditis (de Quervain's thyroiditis) | Painful enlargement of the thyroid gland; hypermetabolism; elevated free T4 level, low TSH level; decreased radioactive iodine uptake |
| Acute suppurative thyroiditis | Fever, painful mass in one thyroid gland lobe; normal thyroid function tests and radioactive iodine uptake |
| Toxic adenoma | Solitary thyroid nodule; hypermetabolism; lack of ocular changes; elevated free T4 level, low TSH level |
| Chronic lymphocytic thyroiditis (Hashimoto's disease) | Diffuse enlargement of the thyroid gland with or without clinical features of hypometabolism; normal thyroid function tests or low free T4 level, elevated thyroid autoantibody level |