Thyroid hormone and heart disease

thyroid related heart problems
on Wed 9 May


Thyroid hormone influences the strength and speed of your heartbeat, your blood pressure and your cholesterol level. As a result, too much or too little of this hormone can either


  • masquerade as heart disease
  • cause heart problems
  • make existing heart disease worse


Masquerading as heart disease

The thyroid plays a significant role in the function of your heart so thyroid problems may manifest themselves in everything from heat flutters to chest pain.


Causing heart problems – Hypothyroidism

Having an underactive thyroid gland can affect your heart and circulatory in several ways including:


  • Raised cholesterol which contributes to increased narrowing and hardening of the arteries
  • High blood pressure
  • A slow heart rate
  • Increased fluid around the heart


Subclinical hypothyroidism - which is a precursor to hypothyroidism itself - may also create changes in blood fats and blood vessel function which over the long-term, especially in those aged less than 65 years, can increase the risk of narrowed arteries.


Causing heart problems - Hyperthyroidism

Because an excess of thyroid hormone can cause the heart to beat more quickly and forcefully this can trigger abnormal heart rhythms such as atrial fibrillation (AF).

AF causes the upper chambers of the heart to quiver rather than pump steadily. This increases the dangers of clots forming in slow moving blood and travelling to the brain thus causing a stroke.

It can also cause the heart’s main pumping chamber to pump too fast. This combined with the quivering aorta can then lead to heart failure


Making existing heart disease worse

An underactive thyroid makes bodily functions inefficient and will have a direct effect on muscular function and aerobic capacity so it’s not difficult to see how it can have a negative impact on those with heart problems.


If you already have high blood pressure which has in turn caused narrows arteries, the combination of a quicker, more forceful heartbeat caused by hyperthyroidism can cause angina.


In 2015 a large study which looked at almost 15,000 people, revealed that those with congestive heart failure were at significantly increased risk of death if they also had hypothyroidism.  The lead author of the study Connie Rhee, MD, of Brigham and Women’s Hospital in Boston said


“In heart failure patients, we found that both hypothyroidism overall and subclinical hypothyroidism increased the risk of death,” To view the study please click here


Why would this be? Well of course heart patients are already vulnerable but moreover heart failure is the inevitable conclusion of multiple stresses which have negatively impacted heart function. This can come about through low or high levels of thyroid hormone



If you have heart disease or are at risk of getting this AND you have symptoms that may relate to hypothyroidism or hyperthyroidism you should ask your GP, endocrinologist or cardiac consultant for further tests.



Hypothyroid patients treated with Levothyroxine generally find that this will help, or even reverse heart conditions which have been caused by an underactive thyroid – especially in young individuals.


Several studies have also indicated that levothyroxine treatment of patients with subclinical hypothyroidism has a favourable impact in short-term clinical trials but this has not yet been proven to reverse vascular risk.


In terms of ongoing hyperthyroidism we know that it is very difficult to reverse AF.


Further evidence of the serious effects of hyperthyroidism on cardiac patients was given in a Finnish Study. This was conducted over two decades and looked at 6,000 heart patients with hyperthyroidism and 18,000 without thyroid issues. They additionally compared the results of surgery treatments against those treated with radioactive iodine ablation (RAI).


Having reviewed the Finnish Study,   Dr Ravi Dave MD, director of interventional cardiology at UCLA Medical Center said he believes there are three points that you should keep in mind if newly diagnosed with hyperthyroidism


  • "Know that your risk of heart disease is high and will continue to be so for the next 20 years.
  • After thyroid treatment, any cardiac symptoms will subside but your risk will be lowest if you are fully hypothyroid.
  • The earlier you get treated, the better you will feel."


On top of this of course you should try to live a healthy life in terms of exercise, diets and lifestyle.

To read about this study in more depth please see this article


I hope this has been helpful. 


Although every effort is made to ensure that all health advice on this website is accurate and up to date it is for information purposes and should not replace a visit to your doctor or health care professional.


As the advice is general in nature rather than specific to individuals Dr Vanderpump cannot accept any liability for actions arising from its use nor can he be held responsible for the content of any pages referenced by an external link


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