Hypothyroidism and Moderate Subclinical Hypothyroidism Are Associated with Increased All-Cause Mortality Independent of Coronary Heart Disease Risk Factors: A PreCIS Database Study

BACKGROUND: Thyroid hormones have profound effect on the heart and peripheral vasculature. Hypothyroidism is associated with an increase in a number of coronary heart disease (CHD) risk factors including dyslipidemia, hypertension, and elevated levels of homocysteine. Our objective was to assess the effects of hypothyroidism (thyroid-stimulating hormone TSH: >10 μ U/mL), moderate subclinical hypothyroidism (SCH; TSH: 6.1-10 μ U/mL), and mild SCH (TSH: 3.1-6.0 μ U/mL) on cardiovascular risk factors, CHD prevalence, and all-cause mortality in patients at high risk for CHD seen in a preventive cardiology clinic. METHODS: All patients seen in the Cleveland Clinic Preventive Cardiology clinic have demographic and laboratory tests including TSH and multiple CHD risk factors obtained at the baseline visit. All data are entered into a database (called PreCIS). The social security death index is queried monthly to determine all-cause mortality. RESULTS: Several CHD risk factors including age, male gender, systolic blood pressure, triglycerides, and fibrinogen were more common in hypothyroid patients. Prevalence of CHD was more common in hypothyroid and moderate SCH patients. All-cause mortality was higher in hypothyroid and moderate SCH patients, but not in mild SCH patients. Higher mortality in these groups was observed in both genders, patients under 65 years of age, and patients not on thyroid replacement therapy, but was not observed in patients over 65 years of age. CONCLUSIONS: Hypothyroidism and moderate, but not mild, SCH are associated with increased CHD prevalence and all-cause mortality. These observations suggest patients with moderate, but not mild, SCH and patients at high risk for CHD should be treated with thyroid replacement therapy.