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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