Thyroiditis

Thyroiditis may be classified as acute, subacute, or chronic. Acute thyroiditis, caused by bacterial infection, is extremely rare. Subacute thyroiditis occurs in 2 forms: granulomatous and lymphocytic. Hashimoto thyroiditis is the most common type of chronic thyroiditis.

Patients with subacute granulomatous thyroiditis present with a painful, enlarged gland associated with fever, chills, and malaise. Thyroid function tests may be helpful because they may reveal the unusual combination of an elevated T4 level and a low radioactive iodine uptake. Patients may be hyperthyroid because of the release of hormone from areas of thyroid destruction; pathologic examination reveals granulomatous inflammation. The disease is self-limited, and treatment is symptomatic, with use of either analgesics or, in severe cases, oral corticosteroids. After resolution, transient hypothyroidism (which becomes permanent in 5%–10% of patients) may occur.

Patients with subacute lymphocytic thyroiditis (“painless” thyroiditis), which commonly occurs 2–4 months postpartum in mothers but may occur in isolation, present with symptoms of hyperthyroidism and a normal or slightly enlarged but nontender thyroid gland. Pathologic investigation shows lymphocytic infiltration resembling Hashimoto thyroiditis, suggesting an autoimmune cause. This disease is also self-limited, generally lasting less than 3 months, and treatment is symptomatic. Hypothyroidism may ensue.

Hashimoto thyroiditis is an autoimmune disease that causes goitrous hypothyroidism. Patients have antibodies to thyroid antigens and an increased incidence of other auto-immune diseases. Patients with Hashimoto thyroiditis may present with hypothyroidism, an enlarged thyroid, or both. Pathologic examination reveals lymphocytic infiltration. Treatment is aimed at normalizing hormone levels with thyroid replacement therapy. Patients with enlarged glands and airway obstruction who do not respond to TSH suppression may require surgery. The risk of primary thyroid lymphoma and papillary thyroid cancer is slightly increased in patients with Hashimoto thyroiditis.

Postpartum thyroiditis occurs in approximately 5% of women after delivery (often in subsequent pregnancies) and can cause hyperthyroidism or hypothyroidism (or first one problem and then the other). Postpartum thyroiditis is usually painless and self-limited and is often associated with thyroid peroxidase antibodies.

Excerpted from BCSC 2020-2021 series: Section 1 - Update on General Medicine. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.