Thyrotoxicosis

Thyrotoxicosis is the syndrome that arises from excessive circulating thyroid hormone levels and is usually caused by Graves' disease or toxic nodular thyroid disease, both of which are forms of hyperthyroidism. Other causes of thyrotoxicosis (but not hyperthyroidism) include destructive thyroiditis in which the thyroid is damaged, resulting in leaking of stored thyroid hormone into the circulation. Distinguishing the cause of thyrotoxicosis is an essential initial step in management, once the diagnosis has been confirmed biochemically. In particular, antithyroid drug treatment can cure around 50% of patients with Graves' disease, will only control but not cure nodular thyroid disease, and is useless in destructive thyroiditis. Radioiodine is generally used to treat patients with toxic nodular goitre and Graves' disease which has relapsed but caution is necessary in those patients with ophthalmopathy; pregnancy and breast feeding are absolute contraindications. Surgery is an alternative to radioiodine but is less used now that the safety of radioiodine is established. Special care is necessary in the management of Graves' disease in pregnancy; the lowest dose of antithyroid drug should be used and measurement of TSH receptor antibodies in the mother can be used to predict the likelihood of the foetus developing neonatal hyperthyroidism.