Mild Thyroid Disorders Can Cause Serious Heart Problems

Mild Thyroid Disorders Can Cause Serious Heart Problems

Los trastornos leves de la tiroides pueden causar problemas cardíacos graves

Types and signaling mechanisms of thyroid hormones. T4 is a prohormone with respect to genomic signaling, but a true fast-acting hormone with respect to type 4 action (which is inhibited by TETRAC iodothyroacetate). Genomic action (type 1, type 2, and mitochondrial signaling) occurs on a slow time scale, while non-genomic effects (type 3 and type 4 signaling) represent a rapid response (A). Thyroid hormone receptors (THRs) usually act as heterodimers. Without binding to thyroid hormone, they block transcription along with corepressors. Iodothyronines displace corepressors and stimulate gene expression along with coactivators (B). The tissue-specific distributions of THR further contribute to the diversity of signaling patterns in the organism (C). AF-1, activation function 1; AF-2, activation function 2; D2, deiodinase type 2; DBD, DNA-binding domain; HAT, histone acetyltransferase; HDAc, histone deacetylase; LBD, ligand binding domain; RXR, retinoid X receptor; TRE, thyroid hormone response element. Credit: Frontiers in Cardiovascular Medicine (2022). DOI: 10.3389/fcvm.2022.942971

It has been known for more than 200 years that severe thyrotoxicosis can lead to cardiac arrhythmia (irregular heartbeat), a leading cause of sudden cardiac death. However, the risk associated with mild hyperthyroidism or hypothyroidism has not been understood until now.

A systematic evaluation of 32 studies with 1.3 million participants shows that even small deviations in thyroid function can increase the risk of serious cardiovascular diseases.

“This puts our understanding of the interaction between the thyroid gland and the heart on a new footing and could pave the way for personalized preventive care,” says Associate Professor Dr. Johannes Dietrich from the Department of Medicine at St Josef’s Hospital, Clinic of Ruhr. University of Bochum, Germany (RUB). The researchers published their work in Frontiers in Cardiovascular Medicine.

For the study, RUB heart and hormone researchers collaborated with a clinical scientist/hormone specialist affiliated with Tan Tock Seng Hospital, Nanyang Technological University Lee Kong Chian School of Medicine, and Duke-NUS School of Medicine. in Singapore.

How should mild thyroid dysfunction be treated?

Today, overt thyroid dysfunction is recognized as an established risk factor for major adverse cardiovascular events (MACE). However, the situation remained equivocal in mild thyroid dysfunction.

“While in some studies, minimal elevations of thyroid hormones and even high normal concentrations within the reference range for healthy people predicted an increased risk of sudden cardiac deathother studies had not shown such a correlation,” explains Johannes Dietrich. Until very recently, the jury was still out on whether to treat people with subclinical forms of hyperthyroidism and hypothyroidism.

To gain a better understanding, a new systematic review by the international team analyzed the results of 32 studies on this topic. In a statistical evaluation combined with consecutive meta-analyses, the researchers found both subclinical hypothyroidism and subclinical hyperthyroidism to predict cardiovascular mortality risk. In particular, serum concentrations of free thyroid hormone T4 (FT4) were directly correlated with the probability of cardiac death and other adverse cardiovascular events.

two different patterns

“The results suggest that cardiovascular risk increases continuously with FT4 concentration, whereas there is a complex U-shaped risk relationship with control concentration. hormone thyrotropin, i.e. TSH,” elaborates Johannes Dietrich. This dualism can be explained by two different patterns of thyroid-mediated arrhythmia.

In one form (“dyshomeostatic type”), primary thyroid disease directly elevates thyroid hormone levels and thus increases cardiovascular risk. In the other form (“allostatic type”), Genetic factors, chronic stress and psychological tension increase the set point of the regulatory circuit between the pituitary gland and the thyroid glandso that the increased FT4 concentration indirectly also promotes the arrhythmia.

“The results of this study could pave the way toward a personalized preventive strategy for cardiac outcomes,” the authors conclude. “Furthermore, thyroid function could serve as a biomarker for the respective mechanism of origin in patients harboring cardiac arrhythmiahelping to personalize the individually optimized medication regimen.


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More information:
Patrick Müller et al, Minor disturbances of thyroid homeostasis and major cardiovascular endpoints: physiological mechanisms and clinical evidence, Frontiers in Cardiovascular Medicine (2022). DOI: 10.3389/fcvm.2022.942971

Citation: Mild Thyroid Disorders Can Cause Severe Heart Problems (Oct 24, 2022) Retrieved Oct 24, 2022 from https://medicalxpress.com/news/2022-10-mild-thyroid-disorders-severe-heart .html

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