Description

Inflammation of the thyroid gland that may be painful or painless:

• Thyroiditis with thyroid pain:
  • Subacute granulomatous thyroiditis (nonsuppurative thyroiditis, de Quervain thyroiditis, or giant cell thyroiditis): Self-limited; viral upper respiratory infection (URI) prodrome, small painful goiter, symptoms and signs of thyroid dysfunction (variable) (1)
  • Infectious/Suppurative thyroiditis:
    • Bacterial, fungal, mycobacterial, or parasitic infection of the thyroid
    • Most commonly associated with Streptococcus pyogenes, Staphylococcus aureus, and S. pneumoniae.
  • Radiation-induced thyroiditis: From radioactive iodine therapy (1%) or external irradiation for lymphoma and head/neck cancers
• Thyroiditis with no thyroid pain:
  • Hashimoto (autoimmune) thyroiditis (chronic lymphocytic thyroiditis): Most common etiology of chronic hypothyroidism; autoimmune disease; 90% of patients with high-serum antithyroid peroxidase (TPO) antibodies
  • Postpartum thyroiditis: Occurs within 1 year postpartum (or after spontaneous/induced abortion)
  • Painless (silent) thyroiditis (subacute lymphocytic thyroiditis): Mild hyperthyroidism, small painless goiter, and no Graves ophthalmopathy/pretibial myxedema (1)
  • Riedel (fibrous) thyroiditis: Rare inflammatory process involving the thyroid and surrounding cervical tissues; is associated with various forms of systemic fibrosis (2); presents as a firm mass in the thyroid commonly associated with compressive symptoms. May present with dyspnea, dysphagia, hoarseness, and aphonia, caused by local pressure/infiltration of the advancing fibrotic process with characteristic biochemical abnormalities, such as hypocalcemia and hypothyroidism (2).
  • Drug-induced thyroiditis: Interferon-α, interleukin-2, amiodarone, or lithium

Epidemiology

• Subacute granulomatous thyroiditis: Most common cause of thyroid pain; peaks during summer; incidence: 3/100,000/year; female:male 4:1; peak age: 40–50 years
• Suppurative thyroiditis: Commonly seen with pre-existing thyroid disease/immunocompromise
• Hashimoto thyroiditis: Peak age of onset, 30–50 years; can occur in children; primarily a disease of women (sex ratio 7:1)
• Postpartum thyroiditis: Female only; occurs within 12 months of pregnancy 8–11% of pregnancies; occurs in 25% with type 1 diabetes mellitus
• Painless (silent) thyroiditis: Female:Male 4:1 with peak age 30–40; common in areas of iodine sufficiency
• Reidel thyroiditis: Female:Male 4:1; highest prevalence age 30–60 years

Risk Factors

• Hashimoto disease: Family history of thyroid/autoimmune disease, personal history of autoimmune disease (type 1 diabetes, celiac disease), high iodine intake, cigarette smoking, selenium deficiency
• Subacute granulomatous thyroiditis: Recent viral respiratory infection
• Suppurative thyroiditis: Congenital abnormalities (persistent thyroglossal duct/piriform sinus fistula), greater age, immunosuppression
• Radiation-induced thyroiditis: High-dose irradiation, younger age, female sex, pre-existing hypothyroidism
• Postpartum thyroiditis: Smoking, history of spontaneous/induced abortion
• Painless (silent) thyroiditis: Iodine-deficient areas

Genetics
Autoimmune thyroiditis is associated with the CT60 polymorphism of cytotoxic T-cell lymphocyte–associated antigen 4. Also associated with HLA-DR4, -DR5, and -DR6 in whites.

General Prevention

Selenium may decrease inflammatory activity in pregnant women with autoimmune hypothyroidism and may reduce postpartum thyroiditis risk in those positive for TPO antibodies (3).

Etiology

• Hashimoto disease: Antithyroid antibodies may be produced in response to an environmental antigen and crossreact with thyroid proteins (molecular mimicry). Precipitating factors include infection, stress, sex steroids, pregnancy, iodine intake, radiation exposure.
• Subacute granulomatous thyroiditis: Probably viral
• Postpartum thyroiditis: Probably autoimmune
• Painless (silent) thyroiditis: Autoimmune

Commonly Associated Conditions

Postpartum thyroiditis: Family history of autoimmune thyroid disease; HLA-DRB, -DR4, and -DR5