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Hypothyroidism

(Hashimoto's Thyroiditis; Underactive Thyroid)

Definition

The thyroid gland is a butterfly-shaped gland in the front of the neck. It produces hormones that control metabolism. Hypothyroidism results when the thyroid gland doesn't produce enough thyroid hormone. The most common form of hypothyroidism is Hashimoto thyroiditis.

Thyroid Gland
thyroid gland male

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Causes  ^

Hashimoto thyroiditis is an autoimmune disorder. The immune system produces antibodies that attack cells of the thyroid gland.

Hypothyroidism may also be caused by:

  • Congenital defects of the gland or how it works
  • Iatrogenic—occurs as the result of surgery or radiation therapy for thyroid cancer treatment
  • Iodine deficiency—rare in the US
  • Pituitary deficiency
  • Unknown reasons

Risk Factors  ^

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

Symptoms  ^

You may not have symptoms of hypthyroidism. In those that have symptoms, hypothyroidism may cause:

Symptoms of severe or long-term hypothyroidism causes:

Diagnosis  ^

You will be asked about your symptoms and medical history. A physical exam will be done.

Tests may include blood tests to check levels of thyroid stimulating hormone (TSH), and/or free T4. Other tests may be recommended to rule out health conditions that are similar to hypothyroidism.

Treatment  ^

Thyroid replacement therapy involves taking medications that replace the function of the thyroid gland. This therapy may also prevent cancer cell growth in people who had surgery or radiation treatment for thyroid cancer.

People with Hashimoto thyroiditis are monitored as long as they have normal thyroid function and remain symptom-free. Once function decreases or symptoms appear, treatment is started with thyroid replacement therapy.

Prevention  ^

There are no current guidelines to prevent hypothyroidism.

The American Academy of Pediatrics and United States Preventive Services Task Force recommend screening all newborns for congenital hypothyroidism. If you are at high risk for developing hypothyroidism, talk to your doctor about annual screening.

RESOURCES:

The American Thyroid Association
http://www.thyroid.org

Office on Women's Health
http://womenshealth.gov

CANADIAN RESOURCES:

Canadian Institute for Health Information
http://www.cihi.ca

Thyroid Foundation of Canada
http://www.thyroid.ca

REFERENCES:

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: http://www.ebscohost.com/dynamed. Updated October 21, 2015. Accessed December 14, 2015.

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: http://www.thyroid.org/thyroid-hormone-treatment. Accessed December 14, 2015.

Last reviewed December 2015 by Kim A. Carmichael, MD  Last Updated: 12/14/2015