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Hypothyroidism and the Heart - Symptoms and Treatments

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Hypothyroidism causes changes in the functioning of the heart or can worsen existing cardiac disease.

Medically reviewed by

Dr. Yash Kathuria

Published At August 7, 2023
Reviewed AtAugust 7, 2023


Hypothyroidism refers to an underactive thyroid gland with reduced production of thyroid hormones in the body. Thyroid hormones help regulate basal metabolic rate, and the decreased levels of thyroid hormones can affect various body organs, and the body functioning is slowed down. A hypothyroid state can cause cardiovascular changes like reduced heart rate, cardiac output, and changes in blood pressure.

What Is Hypothyroidism?

This condition develops when the thyroid gland does not produce and release enough thyroid hormone. The thyroid gland releases hormones called tetraiodothyronine (T3) and triiodothyronine(T4). These hormones help regulate metabolism and control body temperature and heat. The pituitary gland regulates the thyroid hormone level in the blood. When the levels of thyroid hormones are very less in the bloodstream, it produces a hormone called thyroid stimulating hormone (TSH) and leads to the production of thyroid hormones.

The common symptoms of hypothyroidism include

  • Fatigue.

  • Weight gain.

  • Dry skin.

  • Thinning of hair.

  • Irregular menstrual cycles.

  • Slowed heart rate.

  • Depression.

  • Muscle and joint pain.

  • Cold intolerance

How Does Hypothyroidism Affect the Heart?

Decreased levels of thyroid hormones slow down the body's metabolism and affect various systems in the body. In the cardiovascular system, the changes seen are slowing down the heart rate, arteries being made less elastic, and increased cholesterol levels narrowing the arteries and making them more challenging for the blood to flow. It makes the heart pumping less efficient, and the patient will experience shortness of breath while doing exercises.

The underactive thyroid gland can produce high levels of low-density lipoprotein or LDL, also called bad cholesterol. This, in turn, leads to a high risk of heart disease and heart failure.

Thyroid hormones can change the cardiovascular system and affect cardiac function. Thyroid hormones can affect the renin-angiotensin-aldosterone system, and the hypothyroid condition causes decreased renin levels.The associated changes are:

  • Decreased cardiac output.

  • Reduced availability of endothelial nitric oxide.

  • Increased systemic vascular resistance.

  • Narrow pulse pressure.

  • Increased diastolic pressure.

  • Atherosclerosis.

  • Increased risk of coronary artery diseases.

  • Hypothyroidism affects molecular mechanisms, and changes include

    • Endothelial dysfunction.
    • Nitric oxide production decreased.
    • Smooth muscle relaxation is decreased.
    • Vascular smooth muscle relaxation decreased.
  • Hypothyroidism affects lipid metabolism, and the changes include
    • Increased total cholesterol.
    • Increased low-density lipoprotein.
    • Increased level of homocysteine.

What Are the Cardiac Symptoms Seen in Hypothyroidism?

  • Swelling or Edema - Commonly seen in cases of worsening heart failures. It is caused by the accumulation of proteins and molecules around the cells.

  • Heart failure - This can occur newly or can worsen the underlying heart disease.

  • Heart Arrhythmia - Causes irregularities in the heartbeat.

  • High Diastolic Blood Pressure - Arteries become narrow and thick and raise blood pressure.

  • Dyspnea - Also called shortness of breath, difficulty in doing exercises is due to weak skeletal muscles. In people with heart disease, this will worsen the condition.

  • Slow Heart Rate - Also called bradycardia, it is regulated by the thyroid hormones. In these patients, the heart rate is slower than the normal range.

  • Worsening the Condition of Coronary Artery Diseases - Hypothyroidism causes chest discomfort. The C- reactive protein level and LDL levels are increased.

  • The hypothyroid condition affects cardiac contractility and impairs cardiac muscle relaxation. In patients with diastolic hypertension, it can even affect the myocardial diastolic function. This can further lead to reduced cardiac output and reduced heart rate.

  • Hypothyroidism is accompanied by increased risk factors for cardiovascular diseases like arrhythmia.

  • Subclinical hypothyroidism, also called mild thyroid failure, is where the peripheral thyroid levels are in the normal range while the serum TSH levels are mildly elevated. The risk of coronary artery disease increases in subclinical hypothyroidism.

  • With advancing age, the prevalence of hypothyroidism increases, and the level of TSH also increases and is more likely to cause cardiovascular changes in older people.

What Is the Effect of Thyroid Treatment on the Heart?

  • The treatment with Levothyroxine has been shown to improve the cardiac problems associated with it.

  • The cholesterol level, hypertension, and heart rate are regulated. Cardiomyopathic patients with thyroid also showed good responses on treatment with Levothyroxine.

  • In patients with myocardial ischemia, Levothyroxine should begin with low doses and gradually increase when a euthyroid state is achieved.

  • In patients with subclinical hypothyroidism, beneficial improvements were seen with Levothyroxine.

How to Reduce the Risk of Hypothyroidism?

  • Diet - Following a strict diet, with limited consumption of processed food and sugar. Excessive sugar intake can lead to inflammation, and the hypothyroid state is worsened.

  • Cruciferous Vegetables - Excessive consumption of cruciferous vegetables like cabbage and broccoli can affect thyroid production. They can also be referred to as goitrogens. Always advised to limit the intake of these vegetables.

  • Stress - Stress can cause an imbalance in hormone levels and can cause thyroid hormone resistance. It is important to reduce the stress to balance the hormone levels. Yoga, meditation, and changes in life situations can help to manage stress.

  • Exercise - Exercising helps to boost body metabolism and helps to maintain body weight. This can help in the proper production of thyroid hormones.

  • Body Weight - Maintaining a healthy weight should be considered when treating thyroid dysfunction.

  • Swollen neck or a lump in the thyroid gland should be noticed and treated.

  • Significant weight changes are either overweight or underweight despite proper diet and exercise.

  • Constantly tired and sleepy all day.

  • Irregularities in the menstrual cycle.

  • Tremor - involuntary shaking movements of hands, legs, or face.

  • Heart palpitations - a sensation of heart pounding.

  • Temperature intolerance to heat or cold.

  • Thinning of hair or other hair changes.

  • Irregularities in bowel movement.

  • Familial history of the thyroid.


The thyroid gland is an endocrine gland situated at the back of the throat that helps to regulate vital functions. Hypothyroidism resulting from reduced thyroid hormone levels can affect various organs, including the heart. It can cause irregularities in the heart function or can aggravate the existing heart disease. Managing the hypothyroid condition is important as it will help to reduce the risk of cardiac diseases.

Dr. Yash Kathuria
Dr. Yash Kathuria

Family Physician


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