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Systematic review reveals new connections between the thyroid and the heart
Systematic review of 32 studies involving 1.3 million participants reveals new connections between the thyroid and the heart. It has been known for more than 200 years that severe thyrotoxicosis can lead to cardiac arrhythmias (irregular heartbeats), a leading cause of sudden cardiac death. However, the risk associated with mild hyperthyroidism or hypothyroidism has not been understood. A systematic evaluation of 32 studies with 1.3 million participants shows: Even small deviations in thyroid function can increase the risk of serious cardiovascular diseases. This puts our understanding of the interaction between the thyroid and the heart on a new basis and could pave the way to personalized prevention.” Dr. …
Systematic review reveals new connections between the thyroid and the heart
Systematic review of 32 studies involving 1.3 million participants reveals new connections between the thyroid and the heart.
It has been known for more than 200 years that severe thyrotoxicosis can lead to cardiac arrhythmias (irregular heartbeats), a leading cause of sudden cardiac death. However, the risk associated with mild hyperthyroidism or hypothyroidism has not been understood. A systematic evaluation of 32 studies with 1.3 million participants shows: Even small deviations in thyroid function can increase the risk of serious cardiovascular diseases.
This puts our understanding of the interaction between the thyroid and the heart on a new basis and could pave the way to personalized prevention.”
Dr. Johannes Dietrich, Associate Professor, Medical Department of the St. Josef Hospital, Ruhr University Hospital Bochum, Germany (RUB)
The researchers published their work on August 15, 2022 in the journal Frontiers in Cardiovascular Medicine.
For the study, RUB heart and hormone researchers worked with a clinician scientist/hormone specialist from Tan Tock Seng Hospital, the Lee Kong Chian School of Medicine at Nanyang Technological University and the Duke-NUS Medical School in Singapore.
How should mild thyroid dysfunction be treated?
Obvious thyroid dysfunction is now considered an established risk factor for major adverse cardiovascular events (MACE). However, with mild thyroid dysfunction, the situation remained unclear. “While in some studies minimal increases in thyroid hormones and even high-normal concentrations within the reference range for healthy people predicted an increased risk of sudden cardiac death, other studies had not shown such a connection,” explains Johannes Dietrich. Until recently, it was unclear whether patients with subclinical forms of hyperthyroidism and hypothyroidism should be treated.
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To gain a better understanding, a new systematic review by the international team analyzed the results of 32 studies on the topic. In a pooled statistical analysis followed by a meta-analysis, the researchers found both subclinical hypothyroidism and subclinical hyperthyroidism to predict the risk of cardiovascular mortality. In particular, serum concentrations of free thyroid hormone T4 (FT4) were directly correlated with the likelihood of cardiac death and other adverse cardiovascular events.
Two different patterns
“The results indicate that the cardiovascular risk increases continuously with the FT4 concentration, while there is a complex U-shaped risk relationship with the concentration of the control hormone thyrotropin, i.e. TSH,” explains Johannes Dietrich. This dualism can be explained by two different patterns of thyroid-mediated arrhythmia.
In one form (“dyshomeostatic type”), primary thyroid disease directly increases the concentration of thyroid hormones and thereby increases cardiovascular risk. In the other form (“allostatic type”), genetic factors, chronic stress and psychological stress increase the setpoint of the control circuit between the pituitary and thyroid, so that the indirectly increased FT4 concentration also promotes arrhythmias.
Individual prevention and treatment
“The results of this study could pave the way to a personalized prevention strategy for heart problems,” the authors conclude. “In addition, thyroid function in patients with cardiac arrhythmias could serve as a biomarker for the respective development mechanism and help to create an individually optimized medication regimen.”
Source:
Reference:
Müller, P., et al. (2022) Minor disturbances of thyroid homeostasis and important cardiovascular endpoints - physiological mechanisms and clinical evidence. Frontiers in cardiovascular medicine. doi.org/10.3389/fcvm.2022.942971.
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