Description

Inflammation of the thyroid gland that may be painful or painless and characterized by dysfunction

• Thyroiditis with thyroid pain include
  • Subacute granulomatous thyroiditis (nonsuppurative thyroiditis, de Quervain thyroiditis, or giant cell thyroiditis): self-limited; viral URI prodrome, symptoms and signs of thyroid dysfunction (variable)
  • Infectious/suppurative thyroiditis
• Can be due to bacterial, fungal, mycobacterial, or parasitic infection of the thyroid
• Most commonly associated with Streptococcus pyogenes, Staphylococcus aureus, and Streptococcus pneumoniae
  • Radiation-induced thyroiditis: from radioactive iodine therapy (1%) or external irradiation for lymphoma and head/neck cancers
• Thyroiditis with no thyroid pain include
  • Hashimoto (autoimmune) thyroiditis (chronic lymphocytic thyroiditis): most common etiology of chronic hypothyroidism; autoimmune disease; 90% of patients with high-serum anti-thyroid peroxidase (TPO) antibodies
  • Postpartum thyroiditis: episode of thyrotoxicosis, hypothyroidism, or thyrotoxicosis followed by hypothyroidism in the 1st year postpartum or after spontaneous/induced abortion in women who were without clinically evident thyroid disease before pregnancy
  • Painless (silent) thyroiditis (subacute lymphocytic thyroiditis): mild hyperthyroidism, small painless goiter, and no Graves ophthalmopathy/pretibial myxedema
  • Riedel (fibrous) thyroiditis: rare inflammatory process involving the thyroid and surrounding cervical tissues; associated with various forms of systemic fibrosis; presents as a firm mass in the thyroid commonly associated with compressive symptoms (dyspnea, dysphagia, hoarseness, and aphonia) caused by local infiltration of the advancing fibrotic process with hypocalcemia and hypothyroidism
  • Drug-induced thyroiditis: interferon-α, interleukin-2, amiodarone, kinase inhibitors, 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 to 50 years
• Suppurative thyroiditis: commonly seen with preexisting thyroid disease/immunocompromise
• Hashimoto thyroiditis: peak age of onset, 30 to 50 years; can occur in children; primarily a disease of women; female > male (7:1)
• Postpartum thyroiditis: female only; occurs within 12 months of pregnancy in 8–11% of pregnancies; occurs in 25% with type 1 diabetes mellitus; incidence is affected by genetic influences and iodine intake.
• Painless (silent) thyroiditis: accounts for 1–5% of cases; female > male (4:1) with peak age 30 to 40 years; common in areas of iodine sufficiency
• Reidel thyroiditis: female > male (4:1); highest prevalence age 30 to 60 years

Etiology and Pathophysiology

• Hashimoto disease: Antithyroid antibodies may be produced in response to an environmental antigen and cross-react with thyroid proteins (molecular mimicry). Precipitating factors include infection, stress, sex steroids, pregnancy, iodine intake, and radiation exposure.
• Subacute granulomatous thyroiditis: probably viral
• Postpartum thyroiditis: autoimmunity-induced discharge of preformed hormone from the thyroid
• Painless (silent) thyroiditis: autoimmune

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

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 or HLA-B35
• Suppurative thyroiditis: congenital abnormalities (persistent thyroglossal duct/pyriform sinus fistula), greater age, immunosuppression
• Radiation-induced thyroiditis: high-dose irradiation, younger age, female sex, preexisting hypothyroidism
• Postpartum thyroiditis: smoking, history of spontaneous/induced abortion
• Painless (silent) thyroiditis: iodine-deficient areas

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.

Commonly Associated Conditions

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