Thyrotoxicosis

Thyrotoxicosis affects 1% of women and 0.1% of men. The most common causes are Graves' disease and toxic nodular thyroid disease (caused by a multinodular goitre or an adenoma), but it is important to distinguish these types of disease from destructive thyrotoxicosis, which is usually self-limiting and caused by transient autoimmune destruction, viral infection or amiodarone. About one-half of patients with Graves' disease treated with antithyroid drugs are cured, whereas these drugs achieve only temporary biochemical control of hyperthyroidism in toxic nodular disease. Carbimazole is the first-line treatment in the UK, whereas methimazole and propylthiouracil are more commonly used elsewhere. Relapse is usually treated with radioactive iodine or surgery, both of which carry a high rate of subsequent hypothyroidism. Radioiodine may also cause worsening of thyroid-associated ophthalmopathy, particularly in patients who smoke. Radioiodine is first-line treatment in toxic nodular disease. Corticosteroids are used to treat severe cases of viral thyroiditis and the destructive thyroiditis that can accompany amiodarone treatment, though the latter must be distinguished from iodine-induced hyperthyroidism, which can also occur with this drug, and may require treatment with potassium perchlorate in addition to high doses of antithyroid drugs.