[CME: Thyrotoxicosis and Thyroiditis]

Hyperthyroidism is caused by an increased synthesis of thyroid hormones or release of preformed thyroid hormones due to destruction of thyroid tissue, or there is an exogenous extrathyroidal source. The term thyroiditis describes a heterogeneous group of disorders, which result in destruction of thyroid tissue and release of preformed thyroid hormones. Although a less common condition, a thyroiditis remains an important differential diagnosis for thyrotoxicosis, and a symptomatic therapy is the cornerstone of treatment. Because of the classical triphasic clinical course a 'wait and see strategy' is reasonable, especially during the first and self-limited hyperthyroid phase. Usually a transient hypothyroid phase follows, before the euthyroid function is restored within a year. However, as permanent hypothyroidism may result, regular follow-up and in that case treatment with levothyroxine is mandatory.