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
- 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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