Thyroid disease.

Hyperthyroidism and hypothyroidism are common disorders in the elderly and may remain unrecognised until a patient presents with an apparently unrelated problem. The finding of an elevated level of thyroid stimulating hormone (TSH) with a normal serum thyroxine (T4) level represents "subclinical hypothyroidism", which does not necessarily require treatment. Iodine can precipitate hyperthyroidism in patients with autonomous thyroid tissue and the iodine-rich antiarrhythmic agent, amiodarone, may cause either hyperthyroidism or hypothyroidism. The metabolism and clearance of numerous therapeutic agents is altered when thyroid status is abnormal, so that dose adjustment may be necessary. In cardiac failure secondary to hyperthyroidism, great care must be taken in prescribing beta-blockers and diuretics; dosage of digitalis preparations may need to be increased. Thyroid replacement therapy can aggravate myocardial ischaemia and it may be appropriate to consider coronary artery bypass grafting before hypothyroidism is fully corrected. Antithyroid drugs, surgery and radioactive iodine all have a place in the treatment of hyperthyroidism in the elderly, depending on factors such as disease severity and the characteristics of the goitre. T4 may be given together with an antithyroid drug in a "block-replace" regimen.