by EBSCO Medical Review Board

Hypothyroidism is when the thyroid gland does not make enough hormones. The thyroid is a butterfly-shaped gland in the front of the neck. A healthy thyroid makes the hormones thyroxine (T4) and triiodothyronine (T3). These play many roles in the body, such as:

  • How many calories a person burns and how much they weigh
  • The speed at which the heart beats
  • The temperature of a person's body
  • How quickly the body breaks down food

If it is not treated, it can lead to many health problems, such as obesity and heart disease.

The Thyroid Gland
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Hashimoto thyroiditis is the most common cause. A problem with the immune system causes it to attack thyroid gland cells.

Other causes are:

  • Subacute thyroiditis —Inflammation of the thyroid gland after a viral upper respiratory tract infection
  • Medicines —Such as those used to treat hyperthyroidism, lithium for mental health problems, and some heart medicines
  • Medical treatments —Medicines, radiation therapy, or surgery to remove part of the thyroid gland
  • Idiopathic thyroid atrophy —The thyroid tissue shrivels up for reasons that are not known
  • Iodine deficiency —The thyroid gland does not get enough iodine to make hormones (rare in the United States)
  • Iodine excess —Foods (such as shellfish) and some medicines (such as cough medicine) that have large amounts of iodine can stop the thyroid from making hormones (rare)
  • Certain illnesses —Cancers and certain infections
  • Pituitary adenoma —A non-cancerous tumor of the pituitary gland causes a problem signaling the thyroid to make hormones
  • Postpartum thyroiditis —The thyroid becomes inflamed after giving birth and does not work as it should
  • Congenital hypothyroidism —When a baby is born with problems making normal amounts of thyroid hormones
What are the risk factors of hypothyroidism?What are the symptoms of hypothyroidism?How is hypothyroidism diagnosed?What are the treatments for hypothyroidism?Are there screening tests for hypothyroidism?How can I reduce my risk of hypothyroidism?What questions should I ask my doctor?Where can I get more information about hypothyroidism?


Chaker L, Bianco AC, et al. Hypothyroidism. Lancet. 2017 Sep 23;390(10101):1550-1562.

Hypothyroidism in adults. EBSCO DynaMed website. Available at: Accessed February 10, 2021.

Hypothyroidism (underactive thyroid). National Institute of Diabetes and Digestive and Kidney Diseases website. Available at: Accessed February 10, 2021.

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