Description

Painful or painless inflammatory dysfunction of the thyroid gland

• 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 is most commonly associated with Streptococcus pyogenes, Staphylococcus aureus, and Streptococcus pneumoniae but can be due to fungal, mycobacterial, or parasitic infections of the thyroid.
• Radiation-induced thyroiditis: from radioactive iodine therapy (1%) or external irradiation
• Painless thyroiditis
  • Hashimoto (autoimmune) thyroiditis (chronic lymphocytic thyroiditis): most common etiology of chronic hypothyroidism; 90% of patients with high-serum antithyroid peroxidase (TPO) antibodies
  • Postpartum thyroiditis (PPT): 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
• Hashimoto thyroiditis (HT): peak onset 30 to 50 years; can occur in children; female > male (7:1)
• PPT: occurs within 12 months of pregnancy in 1–18% of pregnancies
• 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; rare with estimated incidence of 1.06 cases per 100,000 patients

Etiology and Pathophysiology

• Subacute granulomatous thyroiditis: probably viral; can be associated with COVID-19 infection; the mechanism of thyroid injury can be due to direct destruction of thyroid tissue, as well as indirect immune-mediated responses and medicines used to treat COVID-19 (1).
• 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
• Riedel (fibrous) thyroiditis: rare inflammatory process involving the thyroid and surrounding cervical tissues; associated with various forms of systemic fibrosis

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, such as COVID-19 infection, or HLA-B35
• Hashimoto disease: family/personal history of thyroid/autoimmune disease, high iodine intake, cigarette smoking, selenium deficiency

General Prevention

Insufficient evidence to justify the use of vitamin D or selenium supplementation