Prognostic role of sub-clinical hypothyroidism in chronic heart failure outpatients

BACKGROUND: It has been suggested that low thyroid hormones levels may be associated with increased mortality in patients with cardiovascular disease. AIM: To evaluate the prognostic role of thyroid function deficiency in patients with chronic heart failure (CHF). METHODS: We evaluated 338 consecutive outpatients with stable CHF receiving conventional therapy, all of whom underwent a physical examination, electrocardiography and echocardiography. Blood samples were drawn to assess renal function, and Na+, hemoglobin, NT-proBNPs, fT3, fT4 and TSH levels. Patients with hyperthyroidism were excluded. RESULTS: During the follow-up (15+/-8 months), heart failure progression was observed in 79 patients (including 18 who died of heart failure after hospitalisation and six who underwent transplantation). Univariate regression analysis showed that TSH (p<0.0001), fT3 (p<0.0001), fT4 (p=0.016) and fT3/fT4 (p<0.0001) were associated with heart failure progression but multivariate analysis showed that only TSH considered as a continuous variable (p = 0.001) as well as subclinical hypothyroidism (TSH > 5.5 mUI/l; p=0.014) remained significantly associated with the events. CONCLUSIONS: In CHF patients TSH levels even slightly above normal range are independently associated with a greater likelihood of heart failure progression. This supports the need for prospective studies aimed at clarifying the most appropriate therapeutic approach to sub-clinical hypothyroidism in such patients.