Thyroxine Levels Are Linked to Sudden Cardiac Death

Higher levels of free thyroxine (FT4), even with normal thyroid function, are associated with an increased risk of sudden cardiac death, according to new research.

It is well known that thyroid function is associated with cardiovascular disease, but whether thyroid function is a risk factor for sudden cardiac death is less well understood.
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To conduct their study, the researchers analyzed 10,318 participants aged 45 years and older in the Rotterdam Study with either thyrotropin or FT4 measurements and available follow-up data.

After a median 9 years of follow-up, 261 incident sudden cardiac deaths occurred. The researchers found that higher levels of FT4, even in the normal range of thyroid function, were associated with an increased risk of sudden cardiac death.

Adjusting for age or sex and sensitivity analyses did not substantially change the risk estimates.

In euthyroid participants—those with high-normal thyroxine levels—the absolute 10-year risk increased from 1% to 4% with increasing FT4 levels.

“Higher FT4 levels are associated with an increased risk of [sudden cardiac death], even in euthyroid participants,” the researchers concluded.

—Amanda Balbi

Reference:

Chaker L, van den Berg ME, Niemeijer MN, et al. Thyroid function and sudden cardiac death: a prospective population-based cohort study [published September 6, 2016]. Circulation. doi:http://dx.doi.org/10.1161/CIRCULATIONAHA.115.020789.