Thyroid dysfunction, particularly high levels of FT4, was associated with an increased risk for sudden cardiac death (SCD) in a study.

After an average follow-up period of about 9 years, high levels of FT4 were linked with both a higher relative and absolute risk of SCD (HR 1.77 per 1 ng/dL increase of FT4; 95% CI, 1.09-2.86), reported Layal Chaker, MD, of Erasmus University Medical Center in Rotterdam, The Netherlands, and colleagues in Circulation.

A higher risk of SCD was also identified even in participants considered euthyroid, whose FT4 levels were at the high end of normal (HR 2.26 per 1 ng/dL FT4; 95% CI, 1.30-3.94). Euthyroidism was defined by a TSH level of 0.4-4.0 mIU/L.

Overall, participants whose FT4 levels at the top of the normal range had approximately a 2.5 times greater mortality rate due to SCD, compared to those at the low end of the normal range.

“Our study findings suggest that persons with higher thyroid hormone levels, even within what we consider the normal range of thyroid function, have a four-fold increased risk of sudden cardiac death compared to persons with lower thyroid hormone levels,” said Chaker in an interview with MedPage Today.

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