Medicine and Healthcare
Thyroid Disease: The Amiodarone Risk
Young women with congenital heart defects are at increased risk
Scientific name of the study
Thyroid Dysfunction under Amiodarone in Patients with and without Congenital Heart Disease: Results of a Nationwide Analysis
When the heart gets out of rhythm, it often manifests itself as an uncomfortable heart racing or palpitations. Such arrhythmias are among the most common complications in adults with congenital heart defects (ACHD). They can be particularly dangerous for them and therefore belong in the hands of experienced specialists. Countermeasures can be taken either by catheter ablation or by medication. With the latter, however, caution is advised, as a recent study at the Competence Network for Congenital Heart Defects shows.
Discovered By Chance: Active Substance Against Cardiac Arrhythmias
In Germany, for example, they are called Amiogamma®, Amiohexal® or Cordarex®. These are drugs to treat cardiac arrhythmias that are based on the active ingredient amiodarone. This active substance was originally developed for the treatment of angina pectoris until it was discovered by chance that it has an inhibitory effect on ventricular and supraventricular arrhythmias. Since then, it has been popularly prescribed for cardiac arrhythmias originating in the myocardial tissue above the ventricles. Especially in patients with congenital heart defects, amiodarone is often the drug of choice because other antiarrhythmic drugs are not an option or simply do not work. However, the iodine-containing drug can cause severe side effects, including impairment of the thyreoid function.
Thyroid Dysfunction Is a Risk
It is known from studies that thyroid dysfunction in patients with congenital heart defects is one of the risk factors associated with increased mortality. How often does this amiodarone side effect occur in patients with congenital heart defects? What are the exact risk factors? And what are the therapeutic consequences of amiodarone-induced thyroid dysfunction? These questions were addressed in one of the most comprehensive studies to date on this side effect of the drug.
National Study Suggests Alternative Forms of Treatment
Based on anonymized data from Barmer Health Insurance, the researchers were able to follow up about 50,000 patients aged 16 and older who had been treated with amiodarone at least once between 2005 and 2018, including 886 patients with congenital heart defects. Thirty-eight percent of those observed without congenital heart defects and 35 percent of those observed with congenital heart defects developed thyroid dysfunction over a 10-year period.
"The incidence of this side effect is basically quite high in both groups. It increases with the duration and frequency of taking the drug. However, younger women in particular with severe congenital heart defects tend to develop thyroid dysfunction under amiodarone. This suggests that we should take a closer look at this patient group and, if possible, preferring catheter ablation over drug treatment in accordance with the guideline recommendations," said lead author Alicia Jeanette Fischer, specialist for Internal Medicine and Cardiology at the ACHD Center of Münster University Hospital, summarizing the findings.
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Good to know
What Does The Thyroid Gland Do?
The thyroid gland has an important control function for the human body. The hormones produced in the thyroid gland affect the heart and circulation, dilate blood vessels, accelerate the heartbeat and regulate blood pressure. They also activate fat and connective tissue metabolism, the sweat and sebaceous glands of the skin and kidney and intestinal activity.
In addition, thyroid hormones play an essential role in many growth processes and they regulate the energy consumption of the entire organism. The hormones provide the drive for the body and psyche at the same time. In the case of hyperfunction (hyperthyroidism), i.e. "too many" hormones, the body and psyche run "overspeed", whereas in the case of hypothyroidism, i.e. “too little” hormones, run "low speed".
Why Does Amiodarone Cause Thyroid Dysfunction?
Amiodarone is an organic chemical compound whose molecular weight is determined to more than one third by iodine. It therefore leads to an excessive intake of iodine, which accumulates permanently in the body’s fat tissue and has a long half-life. Iodine is very important for the function of the thyroid gland.
However, too much of it is harmful and leads to the formation of antibodies that cause an inflammatory reaction in the thyroid gland and disrupt its function. The active ingredient, which is structurally similar to thyroid hormones, also prevents the important conversion of the thyroid hormone thyroxine (T4) to triiodothyronine (T3) by inhibiting the formation of necessary enzymes (deiodinases) in the liver.
Amiodarone can therefore cause damage to the body's defense system in a variety of ways and impair thyroid function. Because women have a greater predisposition to autoimmune thyroid disease, administration of amiodarone in women may not necessarily be the cause of thyroid dysfunction; it may also unmask a preexisting thyroid disease.
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Further Risk Factors Identified
In addition to age and gender, scientists were able to identify further risk factors. Patients with a pacemaker were found to be more susceptible to thyroid dysfunction under amiodarone, as were patients after implantation of a cardioverter defibrillator. Chronic kidney disease as well as alcohol consumption and smoking also favored the development of this side effect.
Joyful Alternatives to Alcohol and Tobacco Consumption
According to Alicia Jeanette Fischer, it is generally a gain in quality of life to exchange the consumption of alcohol and tobacco, including the smoking of e-cigarettes, for joyful activities such as running, walking or hiking, yoga, tai chi, dancing or meditation and a balanced diet rich in vitamins and fiber and low in meat, sugar and salt, as well as water as a thirst quencher, "especially when the body already has to perform amazing things due to a congenital heart defect. We have actually known for thousands of years that we strengthen our bodies and our psyches through exercise, sufficient sleep and good food, and thus noticeably increase our general well-being."
The doctor is well aware of how difficult it can be to completely give up the after-work-beer, wine or cigarettes. "The withdrawal works best when we evaluate it not as a renunciation, but as a reward for our body. We breathe much better, sleep better, can move better and concentrate better."
Restrained Medication Prescription and Continuously Monitored Use
Of concern to the researchers is that catheter ablation was used in only 42 percent of ACHD patients and in 34 percent of all patients followed up. "We were surprised by the relatively frequent administration of amiodarone, especially since catheter ablation is recommended in current guidelines as the treatment of first choice for many arrhythmias," said study leader Professor Gerhard-Paul Diller, ACHD specialist at Münster University Hospital.
Moreover, despite thyroid dysfunction, amiodarone administration was continued in almost half of the patients without congenital heart defects (47 percent) and still in more than a third (38 percent) of the adults with a congenital heart defect. 3.5 percent of ACHD patients underwent thyroid surgery or radiation. For all other patients, the figure was 2.3 percent.
"We strongly advise that amiodarone be used only when no suitable alternatives with a more favorable side effect profile are available. Patients requiring amiodarone should be thoroughly examined for any existing thyroid disease before the first prescription and continuously monitored for thyroid dysfunction," emphasizes Professor Gerhard-Paul Diller. This is even more true for people with specific risk factors, such as younger female patients and patients with complex congenital heart defects, as they may be more susceptible to developing complications, he adds.
Discontinuation of Amiodarone Versus Thyroid Surgery
In both hypothyroidism and hyperthyroidism, discontinuation of amiodarone may lead to recovery of its function. However, because the benefit of discontinuation is time-delayed, the likely recovery of thyroid function must be carefully weighed against the need for treatment with amiodarone in the absence of alternative management options for cardiac arrhythmias due to a congenital heart defect.
The authors of the study were therefore surprised to learn that radiation therapy or thyroid surgery is performed less frequently in adults with congenital heart defects than in all other patients. From their perspective, this is concerning because surgery and radiation are the most effective treatments for hyperthyroidism in many cases.
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Scientific Details of the Study
Learn more about the study design, material and methods, as well as the background of the study:
Publications
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5.4.2022
Thyroid Dysfunction under Amiodarone in Patients with and without Congenital Heart Disease: Results of a Nationwide Analysis.
Fischer AJ, Enders D, Eckardt L, Köbe J, Wasmer K, Breithardt G, De Torres Alba F, Kaleschke G, Baumgartner H, Diller GP
Journal of clinical medicine 11, 7, (2022). Show this publication on PubMed.
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