Thyroid disorders in the elderly. Difficulties in diagnosis and treatment.

The diagnosis and management of disorders of thyroid function in the elderly present particular problems. The diagnosis may be missed because of the insidious onset of the disorder and the tendency to attribute many of the complications of hypo- or hyperthyroidism to other causes. Hyperthyroidism presenting as 'apathetic thyrotoxicosis' is seen much more commonly in elderly subjects than in the young, and unless the clinician is familiar with the clinical presentation, the diagnosis may not be considered. Both disease and concomitantly administered drugs may alter thyroid function tests, and abnormal tests do not necessarily mean hyper-or hypothyroidism. Euthyroid hyperthyroxinaemia is often difficult to distinguish from hyperthyroidism. Hyperthyroidism is usually controlled initially by antithyroid drugs, such as carbimazole, which interfere with the synthesis of thyroid hormone. The patient may start to feel better in 1 to 2 weeks and show objective signs of improvement in 3 to 6 weeks. Propranolol may provide earlier symptomatic relief, but must be used cautiously in older people due to its potential adverse effect on cardiac function. Thyroxine should be introduced slowly in those with hypothyroidism; the initial dose is 0.025 to 0.05 mg daily. Because of the long half-life of thyroxine, the dose is increased every 4 to 6 weeks until the patient is clinically euthyroid and the thyroid stimulating hormone level returns to normal. In elderly people the early treatment of subclinical hypothyroidism is justified.