Association of thyroid dysfunction in individuals ≥ 65 years of age with subclinical cardiac abnormalities

Abstract Context The relationship between thyroid dysfunction and measures of myocardial disease in older individuals remains to be defined. Objective To evaluate the impact of thyroid dysfunction on structure and function of the left-heart chambers and blood markers of cardiac disease. Design Cross-sectional analysis. Setting The Cardiovascular Health Study, a community-based cohort of older individuals recruited from four urban areas in the United States. Patients Of 3163 participants studied, 2477 were euthyroid, 465 had subclinical hypothyroidism (SCH), 47 overt hypothyroidism (OH), 45 endogenous (endo) subclinical hyperthyroidism (endo-SCT), and 129 had exogenous (exo) SCT due to thyroid hormone supplementation. Interventions Clinical evaluation, blood sampling and biomarker measurement, 2-dimensional and speckle-tracking echocardiography. Main outcome measure(s) Left heart myocardial deformation, circulating biomarkers of diastolic overload (NT-proBNP), fibrosis (sST2, gal-3), and cardiomyocyte injury (hs-cTnT). Results SCH was associated with higher NT-proBNP (beta = 0.17, p = 0.004), whereas OH was associated with higher hs-cTnT (beta = 0.29, p = 0.005). There were also suggestive associations of SCH with higher sST2, as well as endo-SCT with higher gal-3 and lower (worse) left atrial reservoir strain. Left ventricular longitudinal strain and end-diastolic strain rate did not differ significantly from euthyroid participants in SCH, OH, or exo-SCT. Conclusions In this free-living elderly cohort, subclinical and overt hypothyroidism were associated with abnormalities of blood biomarkers consistent with diastolic overload and myocardial necrosis respectively, whereas subclinical hyperthyroidism tended to be associated with myocardial fibrosis and decreased left atrial strain. Our findings could represent stage B heart failure and illuminate distinct aspects of the pathobiology of heart disease related to thyroid gland dysfunction with potential clinical implications.