Subclinical hyperthyroidism carries higher overall mortality and cardiovascular risks, a meta-analysis using patient-level data shows.
The study, published by the Archives of Internal Medicine, was designed to resolve conflicting results from earlier meta-analyses, which didn't use patient-level data. This analysis encompassed 10 prospective cohorts with data on over 50,000 people. Compared with euthyroid subjects, those with subclinical hyperthyroidism (defined as thyrotropin levels under 0.45 mIU/L with normal free thyroxine levels) showed higher hazard ratios for total mortality, coronary heart disease mortality, and incident atrial fibrillation. Risks for CHD mortality and atrial fibrillation were even higher at thyrotropin levels below 0.10.
The authors say their results support the advice of recent guidelines to treat subclinical hyperthyroidism. An editorialist recommends considering treatment "especially in elderly patients with cardiac risks, hyperthyroid symptoms, or osteoporosis."
Results Of 52 674 participants, 2188 (4.2%) had subclinical hyperthyroidism. During follow-up, 8527 participants died (including 1896 from CHD), 3653 of 22 437 had CHD events, and 785 of 8711 developed AF. In age- and sex-adjusted analyses, subclinical hyperthyroidism was associated with increased total mortality (hazard ratio [HR], 1.24, 95% CI, 1.06-1.46), CHD mortality (HR, 1.29; 95% CI, 1.02-1.62), CHD events (HR, 1.21; 95% CI, 0.99-1.46), and AF (HR, 1.68; 95% CI, 1.16-2.43). Risks did not differ significantly by age, sex, or preexisting cardiovascular disease and were similar after further adjustment for cardiovascular risk factors, with attributable risk of 14.5% for total mortality to 41.5% for AF in those with subclinical hyperthyroidism. Risks for CHD mortality and AF (but not other outcomes) were higher for thyrotropin level lower than 0.10 mIU/L compared with thyrotropin level between 0.10 and 0.44 mIU/L (for both, P value for trend, ≤.03).