Thyroid Dysfunction and Cardiovascular Events in Patients With Dysglycemia

OBJECTIVES: Subclinical thyroid disease is the most common form of thyroid dysfunction and may be associated with adverse cardiovascular outcomes in people at high risk for cardiovascular events. Our objective in this study was to assess the association of thyroid function and thyroid hormone replacement with cardiovascular outcomes in high-risk individuals with dysglycemia and additional cardiovascular risk factors. METHODS: The relationship between baseline thyrotropin (TSH) level and incidence of the composite outcome of nonfatal myocardial infarction, nonfatal stroke, or cardiovascular death; an expanded composite of this outcome plus revascularization or hospitalization for heart failure; and mortality was assessed in 8,401 ORIGIN trial participants with a baseline measurement of TSH. The hazard of each outcome according to either baseline levothyroxine use or TSH-defined hyperthyroidism, euthyroidism, subclinical hypothyroidism, and overt hypothyroidism was estimated before and after adjustment for baseline demographic and clinical characteristics and treatment allocation. RESULTS: Of all participants, 91.5% were euthyroid, 0.8% were hyperthyroid, 5.5% had subclinical hypothyroidism, and 2.2% had overt hypothyroidism. Subclinical hypothyroidism predicted both the expanded cardiovascular outcome (hazard ratio [HR]=1.24, 95% confidence interval [CI] 1.06 to 1.46) and mortality (HR=1.37, 95% CI 1.12 to 1.67), whereas levothyroxine use predicted fewer deaths (HR=0.72, 95% CI 0.56 to 0.94). CONCLUSION: Subclinical hypothyroidism predicts future cardiovascular events and mortality in people with dysglycemia and other cardiovascular risk factors.