In 2005, heart failure (HF) total-mention mortality in the United States was 292,214 and HF was responsible for 1,106,000 hospital discharges in 2006.1 Altered thyroid function in the absence of primary thyroid disease has been described in HF with low circulating levels of biologically active free triiodothyronine (fT3) in about 30% of patients with chronic HF.2,3 The pattern of low fT3 is associated with poor outcome in HF.4 Brain natriuretic peptide (BNP) elevation in HF has been used for risk stratification and for prognostic considerations.4
Passino and colleagues recently published a prospective trial of BNP and fT3 in 442 consecutive patients with systolic HF and no thyroid disease or treatments that would affect thyroid function.6 The average age of patients was 65±12 years, 75% were male and left ventricular ejection fraction averaged 33±10 with New York Heart Association (NYHA) class I and II in 63% and NYHA class III and IV in 37%. At baseline for the entire group thyroid stimulating hormone (TSH), fT3 and fT4 were 1.97±1.72 mIU/L, 2.34±0.49 ng/L, and 12.5±3.6 ng/L, respectively. BNP was 315±406 ng/L (normal range <40 mg/L). Most of the patients were treated with recommended drugs for HF including furosemide (77%), beta-blockers (78%), angiotensin converting enzymes inhibitors (68%), and spironolactone (53%).
As compared to patients with normal fT3 levels, those with low fT3 levels were more likely to be older (69 vs. 63 years), have a higher NYHA class (2.5 vs 2.3), have higher TSH levels (2.44 vs. 1.76 mIU/L), higher BNP (472 vs. 247 ng/L), lower glomerular filtration rate (56 vs. 79 ml/min), and lower hemoglobin (13.3 vs. 14 g/dL). Free triiodothyronine levels were below the normal reference range in 29.8% of the patients.
In a multivariate model, fT3, BNP, and NYHA class had significantly higher hazard ratios with an inverse relationship for fT3 noted for all-cause and cardiac mortality. During a follow period of up to 7 years, all-cause mortality survival was 73% in patients with normal fT3 and 44% in patients with low FT3. Cardiac mortality survival was 83% in patients with normal fT3 and 61% in patients with low FT3. The combination of fT3 and BNP was the more a powerful predictor of all-cause and cardiac mortality than each factor alone and survival was lowest when BNP was high and fT3 was low (28%) compared to low BNP and normal fT3 (84%).
The authors concluded that BNP and fT3 hold an independent and additive prognostic value in HF. This study suggests that thyroid function should be considered when evaluating heart failure patients and that both BNP and fT3 levels are useful in risk-stratifying a patient with HF.
1. Heart Disease and Stroke Statistics 2008 Update: A Report From the American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Rosamond R, Flegal K, Furie K, et al, for the American Heart Association Statistics Committee and Stroke Statistics Subcommittee. Circulation 2008;117:e25-e146.
2. Klein I, Danzi S. Thyroid disease and the heart. Circulation 2007;116:1725-35.
3. Shanoudy H, Soliman A, Moe S, et al. Early ...