(Hashimoto's Thyroiditis; Underactive Thyroid)


The thyroid gland is a butterfly-shaped gland in the front of the neck. It makes hormones that control metabolism. Hypothyroidism is when the thyroid does not make enough thyroid hormones.

Thyroid Gland

thyroid gland male
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Hypothyroidism may be caused by damage or injury to the thyroid. This may happen with:

  • Disorders of the immune system
  • Congenital defects of the gland or how it works
  • Surgery, medical procedures, or radiation therapy for thyroid treatment

It may also be caused by:

  • Problems with the pituitary glands which sends signals to the thyroid
  • Iodine deficiency—(rare in the US) iodine is needed to make thyroid hormones

In some people, the cause of hypothyroidism may remain unknown.

Risk Factors

Hypothyroidism is more common in women. It is also more common in those aged 65 years and older. Other factors that may increase the chance of hypothyroidism include:


Symptoms may not always appear. When they do, they may include:

Symptoms of severe or long-term hypothyroidism may be:


The doctor will ask about symptoms and past health. A physical exam will be done.

Blood tests can check levels of thyroid hormones. Abnormal levels will suggest a problem with the thyroid. Other tests may be done to rule out other health conditions with similar symptoms.


Medicine will be used to replace the missing thyroid hormones. It should relieve symptoms. The amount of medicine that is needed may change over time. Regular check ups will help treatment stay on track.


There are no steps to prevent hypothyroidism.


American Thyroid Association
Office on Women's Health


Thyroid Foundation of Canada


Escobar-Morreale HF, Botella-Carretero JI, Escobar del Rey F, et al. Treatment of hypothyroidism with combinations of levothyroxine plus liothyronine. J Clin Endocrinol Metab. 2005;90(8):4946-4954.
Hypothyroidism in adults. EBSCO DynaMed website. Available at:
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Accessed September 25, 2020.
Roberts CG, Ladenson PW. Hypothyroidism. Lancet. 2004;363(9411):793-803.
Surks MI, Ortiz E, Daniels GH, et al. Subclinical thyroid disease: scientific review and guidelines for diagnosis and management. JAMA. 2004;291(2):228-238.
Thyroid hormone treatment. American Thyroid Association website. Available at:
Last reviewed September 2020 by EBSCO Medical Review Board Monica Zangwill, MD, MPH