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hypothyroidism

Jan 01, 20242 min read

hypothyroidism

Etiologies

  • Primary (>90% of cases of hypothyroidism; ↓ free T4, ↑ TSH) Goitrous: Hashimoto’s thyroiditis (after hyperthyroid phase of thyroiditis), iodine deficiency, lithium, amiodarone Nongoitrous: surgical destruction, s/p radioactive iodine or XRT, amiodarone
  • Secondary (central): ↓ free T4; TSH low, inappropriately nl, or slightly high (although functionally inactive due to abnormal glycosylation); due to hypothalamic or pituitary failure

Hashimoto’s thyroiditis

Clinical manifestations (Annals 2020;173:ITC1)

  • Early: weakness, fatigue, arthralgias, myalgias, headache, depression, cold intolerance, weight gain, constipation, menorrhagia, dry skin, coarse brittle hair, brittle nails, carpal tunnel syndrome, delayed DTRs (“hung up” reflexes), diastolic HTN, hyperlipidemia
  • Late: slow speech; hoarseness; loss of outer third of eyebrows; myxedema (nonpitting skin thickening due to ↑ glycosaminoglycans); periorbital puffiness; bradycardia; pleural, pericardial, & peritoneal effusions; atherosclerosis
  • Myxedema crisis: vide infra

Diagnostic studies (Lancet 2017;390:1550)

  • ↓ free T4; ↑ TSH in 1º hypothyroidism; ⊕ antithyroid Ab (TPO) in Hashimoto’s thyroiditis
  • May see hyponatremia, hypoglycemia, anemia, ↑ LDL, ↓ HDL and ↑ CK
  • Screening recommended for pregnant women

Treatment of overt hypothyroidism (Endocrine 2019;66:18)

Treatment of overt hypothyroidism (Endocrine 2019;66:18)

Subclinical hypothyroidism (NEJM 2017;376:2556; JAMA 2019;322:153)

Myxedema coma (ie, profound hypothyroidism; Thyroid 2014;24:1670)

Graph View

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