Hypothyroidism

Hypothyroidism 

Updated: 10/12/2022

© Jun Wang, MD, PhD

General features
  • Deficiency of thyroid hormone function
  • Structural or functional derangement that reduces thyroid hormone production
Etiology
  • Primary
Iodine deficiency
Medications: lithium, iodides, etc
Destruction of thyroid parenchyma: Hashimoto thyroiditis, S/P thyroidectomy, radioiodine therapy, etc
Congenital defects of thyroid development
Thyroid hormone resistance
  • Secondary, rare
Pituitary failure
Hypothalamic failure
Clinical presentations
  • Symptoms: Fatigue, loss of energy, weight gain, etc
  • Signs: Slowed speech and movements, nonpitting edema (myxedema), goiter, etc
Cretinism
  • Hypothyroidism in infancy or early childhood
  • Due to an anatomic defect in the gland, an inborn error of thyroid metabolism, or iodine deficiency
  • Impaired development of the skeletal system and central nervous system
  • Severe mental retardation, short stature, coarse facial features, a protruding tongue, and umbilical hernia
Myxedema
  • Thickened, nonpitting edematous changes
Myxedema Coma
  • Altered mental status, hypothermia, and other symptoms related to slowing of function in multiple organs
  • Medical emergency with a high mortality rate
  • See in severe longstanding hypothyroidism
  • May be precipitated by an acute event in a poorly controlled hypothyroid patient, such as infection, surgery, etc
  • Treatment: 
    • Monitor in ICU
    • Thyroid hormone, glucocorticoids, supportive measures, management of coexisting problems (eg, infection)
Key laboratory findings
  • High TSH, usually first positive finding
  • Low thyroxin or FTI
  • If normal T4 or FTI, mild or subclinical
Treatment
  • Hormone replacement



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