Uncertainties about the benefit of treatment in subclinical thyroid dysfunction

The Leiden 85-plus study in the oldest old has observed (a) no relationship between thyroid function and symptoms of depression, cognitive impairment or disabilities in daily life, and (b) increased mortality in subjects with TSH < 0.3 mU/l as well as longer survival in subjects with TSH > 4.8 mU/l. Subclinical hyperthyroidism probably warrants more proactive treatment as other studies have also shown increased mortality to accompany a low TSH, although no randomised trials have been done to prove that early intervention prevents atrial fibrillation or prolongs life. The benefits of treatment for subclinical hypothyroidism at a very advanced age are uncertain, but treatment might well be beneficial in middle-aged subjects as some studies report an increased risk of cardiovascular morbidity and mortality. In all cases, however, it is recommended that underlying thyroid disease be demonstrated before treatment is started.