Hypothyroidism (also called underactive thyroid, low thyroid or hypothyreosis) is a disorder of the endocrine system 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, a feeling of tiredness, constipation, slow heart rate, depression, and weight gain.[3] Occasionally there may be swelling of the front part of the neck due to goitre.[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 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][10] The diagnosis of hypothyroidism, when suspected, can be confirmed with blood tests measuring thyroid-stimulating hormone (TSH) and thyroxine 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 thyroxine and TSH levels.[3] 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.[11] In the United States, hypothyroidism occurs in 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.[12] The word hypothyroidism is from Greek hypo- 'reduced', thyreos 'shield', and eidos 'form'.[13]
^"hypothyroidism - definition of hypothyroidism in English from the Oxford dictionary". OxfordDictionaries.com. Archived from the original on March 11, 2013. Retrieved 2016-01-20.
^ abcdefghijklmnopq"Hypothyroidism". National Institute of Diabetes and Digestive and Kidney Diseases. March 2013. Archived from the original on 5 March 2016. Retrieved 5 March 2016.
^"Psychological symptoms and thyroid disorders". British Thyroid Foundation. 11 September 2019.
^ abPreedy V (2009). Comprehensive Handbook of Iodine Nutritional, Biochemical, Pathological and Therapeutic Aspects. Burlington: Elsevier. p. 616. ISBN 9780080920863.
^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.
^ abSyed 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.
^ abcdGarber 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.
^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.
^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.
^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.
^"Hypothyroidism". Merck Veterinary Manual, 10th edition (online version). 2012. Archived from the original on 2012-08-23. Retrieved 2013-12-25.
^Mosby's Medical Dictionary (9 ed.). Elsevier Health Sciences. 2013. p. 887. ISBN 9780323112581. Archived from the original on 2016-03-07.
diet is the most common cause of hypothyroidism. Hashimoto's thyroiditis is the most common cause of hypothyroidism in countries with sufficient dietary...
synonymously with severe hypothyroidism. However, the term is also used to describe a dermatological change that can occur in hypothyroidism and (rare) paradoxical...
removed, hypothyroidism will inevitably result, and thyroid hormone substitutes will be needed. An underactive thyroid gland results in hypothyroidism. Typical...
[citation needed] Hypothyroidism is common in pregnancy with an estimated prevalence of 2-3% and 0.3-0.5% for subclinical and overt hypothyroidism respectively...
Levothyroxine is typically used to treat hypothyroidism, and is the treatment of choice for people with hypothyroidism who often require lifelong thyroid hormone...
also be useful in treatment. Since hypothyroidism is connected with the release of excess growth hormone, hypothyroidism can be mistaken for acromegaly....
radioiodine treatment of Graves' disease often eventually leads to hypothyroidism. Such hypothyroidism may be diagnosed with thyroid hormone testing and treated...
Maternal hypothyroidism is hypothyroidism in pregnant mothers. Even with appropriate treatment, it may pose risks not only to the mother, but also to the...
thyroid gland at the base of the neck. A goitre, if associated with hypothyroidism or hyperthyroidism, may be present with symptoms of the underlying disorder...
without any clinical symptoms (subclinical hypothyroidism or subclinical hyperthyroidism). In the US, hypothyroidism and hyperthyroidism were respectively...
feline hypothyroidism, is causing symptoms similar to feline dwarfism. Dwarfism has the potential to be mistaken as congenital feline hypothyroidism. Signs...
patient is thought to suffer from hyperthyroidism (overactive thyroid) or hypothyroidism (underactive thyroid), or to monitor the effectiveness of either thyroid-suppression...
of hypothyroidism because there were no accurate, readily available laboratory tests of thyroid function. Many less severe cases of hypothyroidism went...
risk, as this creates future generations of this debilitating disease. Hypothyroidism is a growing problem in the Rhodesian Ridgeback, and this condition...
glycogen: high accumulation in hypothyroidism and low accumulation in hyperthyroidism. Myopathy associated with hypothyroidism includes Kocher-Debre-Semelaigne...
endocrine dysfunction, particularly hypothyroidism. In the 1970s, Barnes published several books arguing that hypothyroidism was underdiagnosed in the U.S....
catabolism. Hypothyroidism can cause both decreased GFR and hypovolemia, but BUN-to-creatinine ratio has been found to be lowered in hypothyroidism and raised...
TSH levels • In hypothyroidism due to end organ failure, administration of TRH produces a prompt increase in TSH • In hypothyroidism due to pituitary...
decompensated form of hypothyroidism and while uncommon, is potentially lethal. A person may have laboratory values identical to a "normal" hypothyroid state, but...
it results from red blood cell breakdown, liver disease, infection, hypothyroidism, or metabolic disorders (pathologic). A bilirubin level more than 34 μmol/L...
phenylketonuria and hypothyroidism, among other congenital disorders. Hypothesis: "The newborns have phenylketonuria and hypothyroidism". Null hypothesis...
Woltman's sign (also called Woltman's sign of hypothyroidism or, in older references, myxedema reflex) is a delayed relaxation phase of an elicited deep...
thyroid hormones. Secondary hypothyroidism occurs when TSH secretion from the pituitary is impaired, whereas tertiary hypothyroidism is the deficiency or inhibition...
loss of the outer third of the eyebrows, and is a classical sign of hypothyroidism or atopic dermatitis, but it can also be detected in lepromatous leprosy...