New York, Sep 8 (IANS) Risk of death from sudden loss of heart function is significantly greater in patients with high thyroid hormone levels, according to a study.

"Our results indicate that thyroid hormone levels may be useful for assessing risk to prevent sudden cardiac death," said Layal Chaker, researcher at the Erasmus University Medical Center, at Rotterdam in the Netherland, in the study, published in the journal Circulation.

Although the link between abnormal levels of thyroid hormone and cardiovascular disease is well established, the hormone's relationship with sudden cardiac death is unclear.

Researchers analysed 10,318 patients with an average age of 65 and more than half were women for the study and linked the association of thyroid-stimulating hormone and free thyroxine thyroid hormone levels in blood samples with sudden cardiac deaths listed on medical records and death certificates.

They found that participants with free thyroxine hormone levels at the high end of the normal range were 2.5 times more likely to die of sudden cardiac death, compared to patients with levels at the lower end.

The ten-year risk of sudden cardiac death was four times greater among patients with higher free thyroxine levels compared to those with lower levels.

The increased risk persisted even after controlling for other risk factors such as high cholesterol and high blood pressure.

"The study suggests more caution is warranted in the treatment of thyroid hormone replacement. Replacement therapy is often aimed at the high normal range which carries a risk of over-treatment," Chaker added.