Study: Subclinical Hypothyroidism Linked to Worse Outcomes with Heart Failure

In patients with preexisting heart failure, higher levels of the thyroid hormones TSH and free T4 are associated with more severe heart failure, according to the results of a recent study. The study also showed that higher free T4 is associated with risk of atrial fibrillation, and subclinical hypothyroidism with TSH ≥ 7.0 mIU/L is associated with worse survival.

While subclinical thyroid dysfunction has been shown to be associated with increased risk of heart failure at TSH levels of >10 mIU/L or <0.1 mU/L, its effects in patients with preexisting heart failure have not been studied.
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To further examine this association, researchers analyzed data from 1382 participants with heart failure enrolled in the Penn Heart Failure Study. Mean age of the participants was 57 years, and most were New York Heat Association class II or III.

Overall, there were 450 composite endpoints over a median of 4.2 years of follow-up. Less than 1% were overtly hyperthyroid, 6% were subclinically hypothyroid, 88% were euthyroid, 5% were subclinically hyperthyroid, and 1% were overtly hyperthyroid. Higher TSH, higher free T4, and lower total T3 were associated with more severe heart failure, however, TSH and total T3 were not associated with atrial fibrillation, while free T4 was. Subclinical hypothyroidism was associated with an increased risk of mortality compared with euthyroidism.

“In patients with preexisting heart failure, both higher TSH and higher free T4 concentrations are associated with more severe heart failure, whereas only higher free T4 is associated with atrial fibrillation. Subclinical hypothyroidism with TSH ≥ 7.0 mIU/L is associated with worse survival in this population. Clinical trials are needed to evaluate optimal thyroid function in patients with heart failure,” the researchers concluded.

—Michael Potts

Reference:

Morley M, Brandimarto J, Cappola TP, Cappola AR. Thyroid dysfunction in heart failure is associated with cardiovascular outcomes: the penn heart failure study. Presented at: ENDO 2017; April 2, 2017; Orlando, Florida. https://plan.core-apps.com/tristar_endo17/abstract/f7e437ee5c2d999047a03154443b62b6.