THYROID-DYSFUNCTION IN THE ELDERLY

Objectives. To determine the prevalence of thyroid dysfunction in inst itutionalised elderly people in Cape Town and to assess the usefulness of an abnormal thyroid-stimulating hormone (TSH) concentration as a s creening test in this group. Design. Cross-sectional survey. Setting. Four old-age homes in Cape Town. Subjects. Old-age home residents aged 60 years and over. Outcome measures. Serum concentrations of TSH, fre e thyroxine and free tri-iodothyronine. Results. Serum TSH estimations were performed on 658 participants, and were abnormal in 103 (15.6%)- 41 (6.2%) being elevated (> 5.0 mu U/ml) and 62 (9.4%) being low (< 0. 4 mu U/ml). There were 3 newly diagnosed cases of hyperthyroidism and 7 of hypothyroidism. Subclinical disease was diagnosed in 40 subjects. The overall prevalence of thyroid dysfunction in this population was 11.2%. In 22 (3.4%) this had previously been recognised, while in 50 ( 7.8%) the dysfunction was newly diagnosed by the current survey. The p ositive predictive Value of a TSH concentration > 20 mu U/ml in predic ting hypothyroidism is 67%, while it will predict 100% of cases of sub clinical hypothyroidism. A TSH concentration < 0.1 mu U/ml will predic t 23% of cases of hyperthyroidism, but 81% of cases of subclinical dis ease. Conclusions. The prevalence of thyroid dysfunction in institutio nalised elderly people in Cape Town is similar to that reported for el derly people in other centres. Thyroid dysfunction had not previously been recognised in approximately two-thirds of the subjects in this st udy. The serum TSH concentration is a reliable screening test for thyr oid dysfunction in the elderly but is less useful if used to identify biochemical thyroid disease. An elevated TSH concentration is a better predictor of thyroid dysfunction in the elderly than a depressed TSH concentration.