Use of sensitive thyrotrophin measurements in an elderly population

The investigation of thyroid disease in the elderly is difficult. Conventional tests are influenced by ill health and abnormal concentrations of thyroid binding proteins. To screen for thyroid disease thyroxine (T4), then tri-iodothyronine (T3) or TSH and an index for binding proteins are normally measured, methods which are expensive and time-consuming. TSH immunoradiometric assays (IRMA) offer the potential of a single test assessment of thyroid function in the elderly. This was assessed by comparing the measurement of IRMA-TSH with T4, T3 and the free thyroxine indices in 290 elderly subjects. Concordant results were obtained in 236 subjects. Non-concordant results were seen in 54 subjects. The commonest cause was sick euthyroid syndrome but 4 cases of high T4 and normal TSH were seen with amiodarone therapy.