Cardiovascular Events in Thyroid Disease: A Population Based, Prospective Study

Abstract

No consensus exists whether subclinical thyroid disease should be treated or just observed. Untreated overt thyroid disease is associated with increased risk of cardiovascular disease, and this study was conducted to assess the risk of cardiovascular events in subclinical thyroid disease. The population-based prospective study was conducted in Denmark. A total of 609 subjects from general practice aged 50 years or above with normal left ventricular function were examined. During a median of 5 years of follow-up, major cardiovascular events were documented. In subjects with abnormal TSH at baseline, information about potential thyroid treatment during follow-up was obtained from case reports and mailings. At baseline, 549 (90.7%) were euthyroid (TSH 0.40-4.00 mU/l), 31 (5.1%) were subclinical hypothyroid (TSH>4.00 mU/l), and 25 (4.1%) were subclinical hyperthyroid (TSH<0.40 mU/l). 1 overt hyperthyroid and 3 overt hypothyroid participants were excluded from the analyses. At baseline, the levels of NT-proBNP were inversely associated with the levels of TSH; the lower the levels of TSH, the higher the NT-proBNP concentration. During follow-up, 88 participants died, 81 had a major cardiovascular event, and 28 had a stroke. The incidence of stroke was increased among subjects with subclinical hyperthyroidism, HR 3.39 (95% CI 1.15-10.00, p=0.027) after adjusting for sex, age, and atrial fibrillation. Subclinical hypothyroidism was not related with any of the outcome measurements. Subclinical hyperthyroidism seems to be a risk factor of developing major cardiovascular events, especially stroke in older adults from the general population with normal left ventricular function.