The results of the new study dictate that the risk of dying due to loss of heart function is far more in individuals that have high levels of thyroid hormones in their bloodstream when compared to those having hormone levels at the lower end.
The malfunctioning of the heart’s normal electrical rhythms prevents the heart from beating and thus, causes cardiac death. A previous research, also published in Circulation back in 2012, revealed that more than 50% of all cardiovascular fatalities are caused by cardiac death. The previous study also stated that, in many cases, symptoms of heart disease weren’t exhibited by patients.
The lead author of the current study, Layal Chaker, M.D., M.Sc., and a doctoral candidate and research fellow in endocrinology and epidemiology at Erasmus University Medical Center Rotterdam (Netherlands), said that researchers currently didn’t have any effective way of predicting sudden cardiac death occurring in the general public. That is why it is crucial to identify additional risk factors. The results of the current study gives an indication that the levels of thyroid hormone inside an individual can help in assessing risk of sudden cardiac arrest, and also preventing it.
The thyroid gland is responsible for the production of thyroid hormone. It is released into the blood in order to aid in the regulation of almost all of the organs present inside the body. This also includes the heart. While previous studies have proven a link to exist between cardiovascular disease and abnormal levels of thyroid hormone, the exact association with sudden cardiac death and hormone levels has remained unclear.
A total of 10,318 patients were analyzed by the researchers in the Rotterdam Study. The Rotterdam Study is a long-term investigation of chronic diseases (including heart diseases) present among elderly and middle-aged people living in the Netherlands. The average age of the participants of the study was 65 years. The total sample consisted of more than 50% women. Almost all of the participants were Caucasian.
During the study, the association of the thyroid stimulating hormone as well as the free thyroxine thyroid hormone levels present in the blood samples of the participants was linked by researchers to the sudden cardiac deaths that were listed on the death certificates and medical records.
The results from an average nine years of follow-up showed that, compared to patients with hormone levels at the lower end, participants were 2.5 times more vulnerable to dying because of sudden cardiac arrest if their free thyroxine hormone levels were at the higher end of the normal range.
The 10-year risk of sudden cardiac death was also found to be 4 times higher in patients with increased levels of free thyroxine hormone. Even controlling some of the other risk factors, such as high blood pressure and high cholesterol, still didn’t reduce the risk of sudden cardiac arrest in such patients. The follow-up showed 261 cases of sudden cardiac death.
Dr. Chaker said that they knew a lot of patients who undergo thyroid hormone replacement therapy are sometimes over-treated and thus, have high levels of thyroid hormone in their blood. The results of the current study suggest greater caution for such patients to lower risk of sudden cardiac arrest.
While a link has been suggested between higher levels of thyroid hormone and risk of sudden cardiac death the researchers of the study noted that more research is required. This is because there might be other factors other than just thyroid hormone levels that could’ve have played a role in such a heart failure. Also, only a single test was used for the study and the hormone levels could’ve changed during the overall time period of the research. Furthermore, the findings of the current study might not apply to other races because most of the participants were Caucasian.