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Hypothyroidism, Adult

Hypothyroidism, Adult is a topic covered in the 5-Minute Clinical Consult.

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Basics

Description

  • Clinical and metabolic state resulting from decreased levels of free thyroid hormone or from resistance to hormone action
  • Primary (intrinsic thyroid disease) or central (secondary or tertiary resulting from hypothalamic-pituitary disease)
  • Subclinical: serum TSH above the upper reference limit with a normal free T4 and normal hypothalamic-pituitary-thyroid axis (1)
  • Overt: elevated TSH, usually >10 mIU/L with a subnormal free T4

Epidemiology

Incidence
  • Women: 3.5 per 1,000 persons per year
  • Men: 0.6 per 1,000 persons per year

Prevalence
  • The National Health and Nutrition Examination Survey III (NHANES III), SHypo (subclinical hypothyroidism) 9.3%, overt 0.3–3.7% in an unselected U.S. population age >12 years, with upper limit TSH 4.5
  • Framingham study, 5.9% of women and 2.3% of men age >60 years had a serum TSH >10 mIU/L.

Etiology and Pathophysiology

  • Primary: abnormality at the thyroid gland (>95% of cases)
  • Most common cause worldwide: environmental iodine deficiency (1)[A]
  • Most common cause in the United States: Hashimoto thyroiditis (chronic autoimmune thyroiditis)
    • Hashimoto is characterized pathologically by infiltration of the thyroid with sensitized T lymphocytes and serologically by circulating antithyroid antibodies.
    • Autoimmunity to the thyroid gland is an inherited defect in immune surveillance, leading to abnormal regulation of immune responsiveness or alteration of presenting antigen in the thyroid (1).
  • Postablative/posttherapeutic: follows radioactive iodine therapy or hemithyroidectomy for hyperthyroidism; radiotherapy or surgery for thyroid cancer, benign nodular thyroid disease or neck malignancies
  • Transient hypothyroidism: De Quervain syndrome (viral), postpartum, silent thyroiditis (2)
  • Drug use: propylthiouracil, methimazole, lithium, amiodarone, antiepileptic drugs and newer chemotherapeutic agents such as tyrosine kinase inhibitors (sunitinib), interleukin-2, or interferon-α
  • Central: hypothyroidism due to insufficient stimulation by TSH of an otherwise normal thyroid gland
  • Can be secondary (level of the pituitary) or tertiary (level of the hypothalamus)
  • Etiology involves genetic defects, tumors, vascular, empty sella syndrome, inflammatory, infiltrative, iatrogenic, posttrauma, or drug related.

Risk Factors

  • Women >60 years of age
  • Personal or family history of autoimmune diseases
  • Pregnant women or those with previous postpartum thyroiditis
  • Previous head or neck irradiation
  • Past history of thyroid dysfunction or thyroid surgery
  • Abnormal thyroid examination, presence of goiter and/or TPOAb positivity
  • Treatment with amiodarone, lithium, interferon-α, sunitinib, or sorafenib
  • Those with Down syndrome or Turner syndrome

Commonly Associated Conditions

  • Type 1 and 2 diabetes
  • Pernicious anemia
  • Primary adrenal failure (Addison disease)
  • Myasthenia gravis
  • Celiac disease
  • Rheumatoid arthritis
  • Systemic lupus erythematosus
  • Vitiligo
  • Depression
  • Genetic syndromes that have multiple autoimmune endocrinopathies (MAE) such as type 1 MAE and type 2 MAE.

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Citation

Stephens, Mark B., et al., editors. "Hypothyroidism, Adult." 5-Minute Clinical Consult, 27th ed., Wolters Kluwer, 2019. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116313/all/Hypothyroidism__Adult.
Hypothyroidism, Adult. In: Stephens MB, Golding J, Baldor RA, et al, eds. 5-Minute Clinical Consult. 27th ed. Wolters Kluwer; 2019. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116313/all/Hypothyroidism__Adult. Accessed April 25, 2019.
Hypothyroidism, Adult. (2019). In Stephens, M. B., Golding, J., Baldor, R. A., & Domino, F. J. (Eds.), 5-Minute Clinical Consult. Available from https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/116313/all/Hypothyroidism__Adult
Hypothyroidism, Adult [Internet]. In: Stephens MB, Golding J, Baldor RA, Domino FJ, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2019. [cited 2019 April 25]. 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 - Stephens,Mark B, ED - Golding,Jeremy, ED - Baldor,Robert A, ED - Domino,Frank J, 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 - 27 DB - Medicine Central DP - Unbound Medicine ER -