Heart failure is usually associated with conditions like high blood pressure and coronary artery disease. But as many as half of heart failure patients could have low levels of the thyroid hormone T3 in their heart tissue. Studies have suggested that low levels of cardiac T3 could be influencing heart dysfunction and symptoms of cardiac disease. Scientists have now found that a common blood test could be used in a new way, as a biomarker to predict when low T3 levels are causing heart trouble. The findings, which have been reported in Frontiers in Physiology, may aid in the creation of new treatments for heart failure that may save lives.
When a person's heart is unable to keep up with the body's needs, they may become short of breath, get a rapid heartbeat, or swollen legs. In recent years, research studies have suggested that low levels of thyroid hormone could be raising the risk of death in patients with heart failure, and that if cardiac thyroid levels are restored to normal, heart function improves significantly. Low cardiac T3 symptoms are also very similar to other disorders that can cause heart failure. Still, doctors are reluctant to prescribe the hormone to heart patients because of the risk of side effects like irregular heartbeat, and little is known about dosage.
"I have been rather obsessed with the need for a serum biomarker for cardiac tissue T3 levels for many years," said the Frontiers study author Martin Gerdes, Ph.D., chair and professor of biomedical sciences at New York Institute of Technology College of Osteopathic Medicine (NYITCOM).
The heart releases a molecule called brain natriuretic peptide (BNP) into the blood when heart failure is happening. "It dawned on me that the clinical literature showed a very consistent inverse relationship between serum T3 and BNP levels," said Gerdes.
In this study, the researchers used a rat model of heart failure to assess BNP levels, heart function, gene expression, and T3 treatment. They showed that a blood test could indicate whether cardiac T3 levels should be altered to improve heart function.
Thyroid hormones and BNP levels are routinely checked in heart patients, making these levels easy to monitor as part of an existing regimen.
"The results were remarkable, suggesting that serum BNP levels can be used to titrate the volume of T3 required," revealed Gerdes. "When T3 treatment led to a reduction in serum BNP levels, this was associated with improved cardiac function and reversal of these heart failure genes. The beauty of this biomarker is that it is already in widespread use, so efficacy could be shown quickly."