Recent findings of researchers at Weill Cornell Medical College show that two gene products, proteins previously known to be essential to the coordinated, rhythmic electrical activity of cardiac muscle, a healthy heartbeat, play a key role in thyroid hormone (TH) biosynthesis. These proteins that are involved in human cardiac arrhythmias, called KCNE2 and KCNQ1, could cause thyroid dysfunction.

     According to Dr. Geoffrey W. Abbott, associate professor of pharmacology in medicine at Weill Cornell, the researchers' findings "demonstrate a novel genetic link between inherited cardiac arrhythmia and thyroid dysfunction."

     The study authors suggest that assessment of the thyroid status of patients with KCNE2- and KCNQ1-linked cardiac arrhythmias could, in some cases, reveal a potential endocrine component to their cardiac arrhythmias that may not have been previously determined. This might indicate treatment of the thyroid condition, offering potentially beneficial effects on cardiac function.

     KCNQ1 and KCNE2 form potassium channels in cardiac muscle that help end each heartbeat in a timely way. Inherited mutations in KCNQ1 and KCNE2 cause ventricular and atrial cardiac arrhythmias. This problem has been presumed to be due entirely to the role of these proteins in cardiac muscle. Now researchers have discovered that KCNQ1 and KCNE2 form a potassium channel in the thyroid gland as well.

     Dr. Abbott says, "When the thyroid does not produce enough TH, a person may experience symptoms such as fatigue and a lowered heart rate, but there is also a more complex interplay between thyroid function, cardiac structure and cardiac arrhythmias. Our new findings may begin to explain some of these interrelationships."

     Dr. Abbott also comments that much additional work must be done before researchers fully understand how inherited mutations in the genes coding these proteins affect human thyroid function, how this in turn influences the health of human heart and other tissues, and how useful their discoveries will be in developing therapies to treat thyroid and thyroid-related human disease.

--Source: "New Genetic Link Between Cardiac Arrhythmias and Thyroid Dysfunction Identified," New York-Presbyterian Hospital/Weill Cornell Medical Center/Weill Cornell Medical College, September 19, 2009