Hyperthyroidism results in greater risk of irregular heart rhythm
Hyperthyroidism or overactive thyroid is a condition when your thyroid gland produces too much of the hormone thyroxin. Hyperthyroidism can accelerate many of your bodies’ functions. This condition has been linked to systolic hypertension, heart failure, rapid heartbeat and atrial fibrillation.
Past studies have shown that subclinical hyperthyroidism (is a mild form of hyperthyroidism in which you do not have any symptoms or the symptoms are mild) is also associated to atrial fibrillation but according to the study’s introduction these studies were small in size.
With that in mind a team of researchers from Denmark aimed their research towards examining the risk of atrial fibrillation in relation to the whole spectrum of thyroid function in a large cohort of patients.
For the study researchers used nationwide registry data and had seen a general practitioner for the first time to evaluate their thyroid during 2000 and 2010 and had a mean age of 50.2 years. Each subject entered the cohort on first thyroid screening and was followed until 31 December 2010, migration from the study area, or death.
During the average follow-up at 5.5 years, 17,154 (2.9%) patients had a hospital diagnosis of first time atrial fibrillation, of which 53% were women. Among the patients with hospital diagnosis, for 52% of the patient’s atrial fibrillation was the main reason for hospitalization.
Among the euthyroid subjects, euthyroid meaning having normal thyroid gland function, 2.9% developed atrial fibrillation. Patients with subclinical hyperthyroidism had showed a 30% increased risk of atrial fibrillation, while patients with high-normal thyroid function had a 12% increased risk.
According to the researchers they had written that their study supports the ongoing evidence that subclinical hyperthyroid and possibly also high normal euthyroid states are risk factors for atrial fibrillation.
The researchers did note that due to the fact their study was an observational study it was not possible to draw direct conclusions on causal relationships of the findings.
In their conclusion the researchers write; “Notably, both subclinical and overt hypothyroidism were associated with lower risk of atrial fibrillation. These results support long term screening for atrial fibrillation in patients with thyroid disease.”
Even after adjusting for known risk factors of atrial fibrillation such as hypertension, heart failure, myocardial infarction, valvular heart disease (damage to or a defect in one of the four heart valve)and diabetes did not change the results.
The researchers also noted “The current study is, to the best of our knowledge, the first to assess the association between the whole spectrum of thyroid disease and the subsequent risk of atrial fibrillation in a population of primary care patients.”
This study is published in the journal BMJ.
Atrial fibrillation (AF) is a common arrhythmia associated with increased morbidity and mortality and its association with hyperthyroidism has been well documented.