High and High-Normal Thyroid Levels Linked To Increased Risk of Sudden Cardiac Death

MedicalResearch.com Interview with:

Layal Chaker, MD, MSc Research and Curriculum Fellow Department of Epidemiology Harvard T.H. Chan School of Public Health Boston, MA

Dr. Layal Chaker

Layal Chaker, MD, MSc
PhD candidate
Department of Endocrinology and Epidemiology
Erasmus Medical Center
Rotterdam, The Netherlands

MedicalResearch.com: What is the background for this study? What are the main findings?

Response: The association of thyroid function with coronary heart disease is well–established but not much was known about the association of thyroid function with sudden cardiac death. We conducted the study with the hypothesis that thyroid hormone levels affect cardiovascular risk factors and therefore could also affect the risk of sudden cardiac death (SCD). We were surprised to see that when we control our analyses for these cardiovascular risk factors, the association of high and high-normal thyroid function with SCD remained similar, suggesting that other pathways could play a role. Thyroid hormone has different effects on the cardiovascular systems and future studies should identify which pathway could be responsible for the increased risk of sudden cardiac death with higher thyroid hormone levels. This could lead to better assessment of individual risk and identify possible prevention targets.

MedicalResearch.com: What should readers take away from your report?

Response: Our study suggests an increased risk of  sudden cardiac death with high and high-normal thyroid function. The increased risk of SCD with thyroid function at the high end of normal are particularly important for patients taking thyroid hormone replacement therapy. Approximately 3 percent of the general population is treated with thyroid medication and numbers are increasing. We also know that a substantial proportion of these patients is over-treated, where thyroid hormone levels are high-normal to high. In these individuals, the thyroid hormone levels are modifiable by decreasing the dose of therapy and thereby perhaps decreasing sudden cardiac death risk.

MedicalResearch.com: What recommendations do you have for future research as a result of this study?

Response: Our study shows that thyroid function at the high end of normal is a risk factor sudden cardiac death. However, we were not able to study the effect of possible treatment of high thyroid function in prevention of sudden cardiac death and this requires further research. Also, more research is needed to unravel the exact pathophysiological mechanisms behind this association.

MedicalResearch.com: Is there anything else you would like to add?

Response: Even though there is a potential risk of  sudden cardiac death with overtreatment of hypothyroidism, this does not mean hypothyroid patients treated with levothyroxine should be undertreated. Hypothyroidism and undertreatment of hypothyroidism also have deleterious effects on the cardiovascular system. Therapy should therefore be aimed at the optimum range of thyroid function.

MedicalResearch.com: Thank you for your contribution to the MedicalResearch.com community.

Citation:

Circulation. 2016 Sep 6;134(10):713-22. doi: 10.1161/CIRCULATIONAHA.115.020789.
Thyroid Function and Sudden Cardiac Death: A Prospective Population-Based Cohort Study.
Chaker L1, van den Berg ME1, Niemeijer MN1, Franco OH1, Dehghan A1, Hofman A1, Rijnbeek PR1, Deckers JW1, Eijgelsheim M1,Stricker BH2, Peeters RP1.

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