Hypothyroidism, Adult
BASICS
DESCRIPTION
- Metabolic state resulting from decreased levels of free thyroid hormone or from resistance to hormone action.
- Subclinical: elevated TSH, normal free T4 (1)
- Overt: elevated TSH, subnormal free T4
EPIDEMIOLOGY
Incidence
- Women: 3.5/1,000 persons per year
- Men: 0.6/1,000 persons per year
Prevalence
ETIOLOGY AND PATHOPHYSIOLOGY
- Primary: abnormality at the thyroid gland (>95% of cases)
- Most common cause worldwide: environmental iodine deficiency
- Most common cause in the United States: Hashimoto thyroiditis (chronic autoimmune thyroiditis) (2)
- Postablative/posttherapeutic
- Transient hypothyroidism: de Quervain syndrome (viral), postpartum (3)
- Drug use: propylthiouracil, methimazole, lithium, amiodarone, antiepileptic drugs, and newer chemotherapeutic agents such as tyrosine kinase inhibitors (sunitinib), interleukin-2, or interferon-α
- Secondary is deficiency of TSH from pituitary gland, tertiary deficiency of TRH from hypothalamus
- Peripheral: T3 and T4 excessively degraded by ectopically produced type 3 iodothyronine deiodinase (rare)
Genetics
RISK FACTORS
- Personal or family history of autoimmune diseases
- External head or neck irradiation
- Treatment with amiodarone, lithium, interferon-α, sunitinib, or sorafenib
- Down syndrome or Turner syndrome
GENERAL PREVENTION
- Iodized salt has significantly decreased iodine-deficient causes of hypothyroidism in western countries.
- Those needing additional supplementations include people consuming unbalanced vegetable-based or salt-restricted diets as well as young females and those pregnant or lactating.
COMMONLY ASSOCIATED CONDITIONS
Autoimmune disorders if cause
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Citation
Domino, Frank J., et al., editors. "Hypothyroidism, Adult." 5-Minute Clinical Consult, 34th ed., Wolters Kluwer, 2026. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116313/all/Hypothyroidism__Adult.
Hypothyroidism, Adult. In: Domino FJF, Baldor RAR, Golding JJ, et al, eds. 5-Minute Clinical Consult. Wolters Kluwer; 2026. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116313/all/Hypothyroidism__Adult. Accessed July 16, 2025.
Hypothyroidism, Adult. (2026). In Domino, F. J., Baldor, R. A., Golding, J., & Stephens, M. B. (Eds.), 5-Minute Clinical Consult (34th ed.). Wolters Kluwer. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116313/all/Hypothyroidism__Adult
Hypothyroidism, Adult [Internet]. In: Domino FJF, Baldor RAR, Golding JJ, Stephens MBM, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2026. [cited 2025 July 16]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116313/all/Hypothyroidism__Adult.
* Article titles in AMA citation format should be in sentence-case
TY - ELEC
T1 - Hypothyroidism, Adult
ID - 116313
ED - Domino,Frank J,
ED - Baldor,Robert A,
ED - Golding,Jeremy,
ED - Stephens,Mark B,
BT - 5-Minute Clinical Consult, Updating
UR - https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116313/all/Hypothyroidism__Adult
PB - Wolters Kluwer
ET - 34
DB - Medicine Central
DP - Unbound Medicine
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