Why does hyperthyroidism cause heart problems

Thyroid and heart

The heart is an essential target organ for thyroid hormones. In interplay with numerous other mechanisms, thyroid hormones regulate the strength of the heart, the heart rate and also the circulating blood volume. Therefore, dysfunction of the thyroid gland always has an impact on the cardiovascular system. Conversely, with all disorders and diseases of the cardiovascular system, a possible connection with the thyroid should always be considered.

Regardless of whether there is an overactive thyroid gland (hyperthyroidism) or an underactive thyroid gland (hypothyroidism), the resulting cardiovascular system symptoms are often different in younger and older patients. As a rule, younger people react much more intensely than older people. For example, younger people who overproduce thyroid hormones (hyperthyroidism) usually suffer much more from palpitations and agitation than older patients, who sometimes have no subjective symptoms at all.

Symptoms of a thyroid dysfunction in the cardiovascular system

In the case of an overactive thyroid (hyperthyroidism), the following phenomena can be observed when examining the circulatory system:

  • Racing heart (accelerated heart rhythm)
  • Cardiac arrhythmias
  • Restlessness / tremors

If the thyroid gland is underactive (hypothyroidism), the following can be observed:

  • Slow pulse
  • Water retention / pasty leg edema
  • Performance degradation
  • Cardiac arrhythmias

Patients with a pre-existing heart disease such as coronary heart disease or who have had a previous heart attack are particularly prone to thyroid dysfunction.

The most common cardiac problem associated with the thyroid is a combination of irregular heartbeat and an overactive thyroid. Particularly in patients with atrial fibrillation (absolute arrhythmia, irregular pulse rate), an additional hyperthyroidism has a very negative impact. Therefore, a sleeping hyperthyroidism (latent hyperthyroidism) should be treated in such patients.

Thyroid and heart drugs

Certain heart medications can also affect thyroid function. This is most often the case with the heart drug amiodarone (trade names e.g. Cordarex, Amiodarone, Cornarone, Amiodura). Amiodarone is used to treat severe cardiac arrhythmias and has a very high iodine content. After prolonged use, due to the excessively high iodine intake, an immunogenic reaction can lead to so-called amiodarone-induced hyperthyroidism even in people who are actually thyroid healthy. Amiodarone is also dangerous if there is already sleeping or manifest hyperthyroidism and the additional iodine intake can lead to a rapid and possibly life-threatening worsening of the hyperthyroidism.

Thyroid function must therefore be checked regularly before and during amiodarone treatment. If there is already latent or manifest hyperthyroidism and there is no good alternative to amiodarone therapy from a cardiological point of view, it is advisable to definitively eliminate the hyperthyroidism as quickly as possible through an operation, radioiodine therapy or, under certain circumstances, thermal ablation.

Other heart medications (e.g. quinidine, digitalis) can increase the effect of thyroid hormones on the heart and thus aggravate, for example, arrhythmias.

Other heart medications, such as beta blockers, can mask the effects of an overactive thyroid gland (hyperthyroidism) on the heart. Beta blockers are therefore also used to treat the consequences of an overactive thyroid on the cardiovascular system. If beta-blockers are discontinued when the hyperthyroidism is unknown, unexpected cardiac arrhythmias can occur.

Hidden thyroid disorders

Pathological changes in the thyroid do not necessarily have to be perceived subjectively. Hidden functional disorders and especially latent hyperthyroidism can, however, have a very unfavorable effect on cardiological symptoms. In addition to the heart drug amiodarone, which is very rich in iodine, the administration of contrast media, which is also very rich in iodine, e.g. during a cardiac catheter examination, can cause acute and sometimes life-threatening heart problems. Therefore, the thyroid gland should also be examined before any heart treatment. (Additional Information)

The combination of thyroid and heart disease may also change the need for treatment. For example, sleeping and asymptomatic hyper- or hypothyroidism in older people is often only observed and controlled, but if there is an additional cardiovascular disease, it may be better for the patient that the thyroid is treated early with medication, surgery or radioiodine therapy becomes.

AUTHOR: Prof. Dr.med. Hans Udo Zieren