Hypothyroidism

Not to be confused with Hyperthyroidism.

Hypothyroidism
Other namesUnderactive thyroid, low thyroid, hypothyreosis
Molecular structure of thyroxine, which is deficient in hypothyroidism
Pronunciation
  • /ˌhaɪpəˈθaɪrɔɪdɪzəm, -poʊ-/[1][2]
SpecialtyEndocrinology
SymptomsFatigue (feeling tired), poor ability to tolerate cold, muscle aches, constipation, weight gain,[3] depression, anxiety, irritability[4]
ComplicationsDuring pregnancy can result in cretinism in the baby[5]
Usual onset> 60 years old[3]
CausesHashimoto's thyroiditis, thyroiditis, surgical removal of thyroid gland, iodine deficiency, lithium treatment[3]
Diagnostic methodBlood tests (thyroid-stimulating hormone, thyroxine)[3]
Differential diagnosisDepression, dementia, heart failure, chronic fatigue syndrome[6]
PreventionSalt iodization[7]
TreatmentLevothyroxine[3]
Frequency0.3–0.4%[8]

Hypothyroidism is an endocrine disease in which the thyroid gland does not produce enough thyroid hormones.[3] It can cause a number of symptoms, such as poor ability to tolerate cold, extreme fatigue, muscle aches, constipation, slow heart rate, depression, and weight gain.[3] Occasionally there may be swelling of the front part of the neck due to goiter.[3] Untreated cases of hypothyroidism during pregnancy can lead to delays in growth and intellectual development in the baby or congenital iodine deficiency syndrome.[5]

Worldwide, too little iodine in the diet is the most common cause of hypothyroidism.[8][9] Hashimoto's thyroiditis, an autoimmune disease where the body's immune system reacts to the thyroid gland,[10] is the most common cause of hypothyroidism in countries with sufficient dietary iodine.[3] Less common causes include previous treatment with radioactive iodine, injury to the hypothalamus or the anterior pituitary gland, certain medications, a lack of a functioning thyroid at birth, or previous thyroid surgery.[3][11] The diagnosis of hypothyroidism, when suspected, can be confirmed with blood tests measuring thyroid-stimulating hormone (TSH) and thyroxine (T4) levels.[3]

Salt iodization has prevented hypothyroidism in many populations.[7] Thyroid hormone replacement with levothyroxine treats hypothyroidism.[3] Medical professionals adjust the dose according to symptoms and normalization of the TSH levels.[12] Thyroid medication is safe in pregnancy.[3] Although an adequate amount of dietary iodine is important, too much may worsen specific forms of hypothyroidism.[3]

Worldwide about one billion people are estimated to be iodine-deficient; however, it is unknown how often this results in hypothyroidism.[13] In the United States, overt hypothyroidism occurs in approximately 0.3–0.4% of people.[8] Subclinical hypothyroidism, a milder form of hypothyroidism characterized by normal thyroxine levels and an elevated TSH level, is thought to occur in 4.3–8.5% of people in the United States.[8] Hypothyroidism is more common in women than in men.[3] People over the age of 60 are more commonly affected.[3] Dogs are also known to develop hypothyroidism, as are cats and horses, albeit more rarely.[14] The word hypothyroidism is from Greek hypo- 'reduced', thyreos 'shield', and eidos 'form', where the two latter parts refer to the thyroid gland.[15]

  1. ^ "hypothyroidism". Dictionary.com Unabridged (Online). n.d.
  2. ^ "hypothyroidism - definition of hypothyroidism in English from the Oxford dictionary". OxfordDictionaries.com. Archived from the original on March 11, 2013. Retrieved 2016-01-20.
  3. ^ a b c d e f g h i j k l m n o p "Hypothyroidism". National Institute of Diabetes and Digestive and Kidney Diseases. March 2021. Archived from the original on 11 March 2025. Retrieved 15 March 2025.
  4. ^ "Psychological symptoms and thyroid disorders". British Thyroid Foundation. 11 September 2019.
  5. ^ a b Preedy V (2009). Comprehensive Handbook of Iodine Nutritional, Biochemical, Pathological and Therapeutic Aspects. Burlington: Elsevier. p. 616. ISBN 9780080920863.
  6. ^ Ferri FF (2010). Ferri's differential diagnosis: a practical guide to the differential diagnosis of symptoms, signs, and clinical disorders (2nd ed.). Philadelphia, PA: Elsevier/Mosby. p. Chapter H. ISBN 978-0323076999.
  7. ^ a b Syed S (April 2015). "Iodine and the "near" eradication of cretinism". Pediatrics. 135 (4): 594–6. doi:10.1542/peds.2014-3718. PMID 25825529. S2CID 27647943.
  8. ^ a b c d Garber JR, Cobin RH, Gharib H, Hennessey JV, Klein I, Mechanick JI, Pessah-Pollack R, Singer PA, Woeber KA (December 2012). "Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association". Thyroid. 22 (12): 1200–35. doi:10.1089/thy.2012.0205. PMID 22954017.
  9. ^ Chakera AJ, Pearce SH, Vaidya B (2012). "Treatment for primary hypothyroidism: current approaches and future possibilities". Drug Design, Development and Therapy (Review). 6: 1–11. doi:10.2147/DDDT.S12894. PMC 3267517. PMID 22291465.
  10. ^ "Hashimoto's Disease". National Institute of Diabetes and Digestive and Kidney Diseases(NIDDK). Retrieved 2024-02-19.
  11. ^ Persani L (September 2012). "Clinical review: Central hypothyroidism: pathogenic, diagnostic, and therapeutic challenges". The Journal of Clinical Endocrinology and Metabolism (Review). 97 (9): 3068–78. doi:10.1210/jc.2012-1616. PMID 22851492.
  12. ^ Cite error: The named reference NICENG145 was invoked but never defined (see the help page).
  13. ^ Cooper, DS, Braverman LE, eds. (2012-07-12). Werner & Ingbar's the thyroid: a fundamental and clinical text (10th ed.). Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins Health. p. 552. ISBN 978-1451120639. Archived from the original on 2016-05-20.
  14. ^ "Hypothyroidism". Merck Veterinary Manual, 10th edition (online version). 2012. Archived from the original on 2012-08-23. Retrieved 2013-12-25.
  15. ^ Mosby's Medical Dictionary (9 ed.). Elsevier Health Sciences. 2013. p. 887. ISBN 9780323112581. Archived from the original on 2016-03-07.
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