Description

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

• Painful thyroiditis
  • Subacute granulomatous thyroiditis (nonsuppurative thyroiditis, de Quervain thyroiditis, 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
• Painless thyroiditis
  • 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 (PPT): 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
  • Palpation thyroiditis: due to palpation of the thyroid gland intra-operatively or during a physical exam or biopsy

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 (HT): peak age of onset, 30 to 50 years; can occur in children; primarily a disease of women; female > male (7:1)
• PPT: 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

• Subacute granulomatous thyroiditis: probably viral
• 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.
• PPT: 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

• 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
• 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
• PPT: smoking, history of spontaneous/induced abortion
• Painless (silent) thyroiditis: iodine-deficient areas

General Prevention

In patients with autoimmune thyroiditis, selenium and vitamin D supplementation may decrease antibody titers (1),(2).

Commonly Associated Conditions

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