Among patients with HF, those with subclinical hypothyroidism and low triiodothyronine concentrations were at elevated risk for worsening HF or death, researchers reported.
Lakshmi Kannan, MD, MSc, from the division of endocrinology, diabetes and metabolism, Perelman School of Medicine, University of Pennsylvania, and colleagues analyzed 1,365 patients from the Penn Heart Failure Study (mean age, 57 years; 35% women) to determine the relationship between thyroid dysfunction and HF/survival outcomes.
Among the cohort, 45% were NYHA class II and 32% were NYHA class III.
Outcomes of interest included severity of HF as determined by NYHA class, atrial fibrillation and a composite of ventricular assist device placement, heart transplantation or death.
According to the researchers, greater HF severity was associated with higher concentration of thyroid-stimulating hormone, higher concentration of free thyroxine and lower concentration of total triiodothyronine (P < .001 for all).
In addition, HF was associated with higher concentration of free thyroxine (P .01), they wrote.
During 4.2 years of follow-up, 462 patients experienced one of the composite outcomes.
After adjustment, compared with those with euthyroidism, patients with subclinical hypothyroidism, defined as thyroid-stimulating hormone of 4.51 mIU/L to 19.99 mIU/L with normal free thyroxine, had increased risk for the composite endpoint (HR = 1.82; 95% CI, 1.27-2.61), according to the researchers.
The elevated risk was observed in the subgroup with thyroid-stimulating hormone of at least 7 mIU/L (HR = 3.25; 95% CI, 1.96-5.39), but not in the subgroup with thyroid-stimulating hormone of 4.51 mIU/L to 6.99 mIU/L (HR = 1.26; 95% CI, 0.78-2.06).
Patients with isolated low triiodothyronine concentrations had higher risk for the composite endpoint than those who did not (HR = 2.12; 95% CI, 1.65-2.72).
“Our data indicate that thyroid function is a key prognostic indicator in patients with pre-existing heart failure,” Kannan and colleagues wrote. “Our findings indicate the need for future studies to explore therapeutic effects of [thyroxine] and [triiodothyronine] administration in heart failure.” – by Erik Swain
Disclosures: The authors report no relevant financial disclosures.