ESSENTIALS OF DIAGNOSIS
Chronic lymphocytic (Hashimoto) thyroiditis is the most common thyroiditis and often progresses to hypothyroidism.
Postpartum thyroiditis and subacute lymphocytic thyroiditis (silent thyroiditis) can cause transient hyperthyroidism due to passive release of stored thyroid hormone.
Thyroid peroxidase antibodies (TPO Ab) or thyroglobulin antibodies (Tg Ab) are usually high.
Painful subacute thyroiditis (de Quervain thyroiditis)
Hallmark is tender thyroid gland with painful dysphagia.
Viral etiology. Antithyroid antibodies are absent or low, distinguishing it from autoimmune thyroiditis.
Infectious (suppurative) thyroiditis
IgG4-related thyroiditis (Riedel thyroiditis)
A. Autoimmune Thyroiditis
Several clinical entities are classified as autoimmune thyroiditis, including chronic lymphocytic thyroiditis, postpartum thyroiditis, and painless (silent) sporadic subacute thyroiditis. Dietary iodine supplementation (especially when excessive) and certain medications can cause autoimmune thyroiditis. The incidence of autoimmune thyroiditis varies by kindred, race, and sex. It is commonly familial. Elevated serum levels of antithyroid antibodies are detectable in the general population in 3% of men and 13% of women. Among United States adults studied, elevated levels of antithyroid antibodies are found in 14.3% of those who self-identify as White, 10.9% as Latinx, and 5.3% as Black. Women over the age of 60 years have a 25% incidence of elevated serum levels of antithyroid antibodies, yet thyroid dysfunction develops in only a small subset of such individuals. However, 1% of the population has serum antithyroid antibody titers greater than 1:640, and they are at particular risk for thyroid dysfunction. Subclinical thyroiditis is extremely common; autopsy series have found focal thyroiditis in about 40% of women and 20% of men. The humoral autoimmunity of autoimmune thyroiditis differs from that of Graves disease, where thyroid-stimulating immunoglobulins (TSI) bind to the TSH receptor in thyroid cell membranes and stimulate the gland to hyperfunction.
Childhood or occupational exposure to head-neck external beam radiation increases the lifetime risk of autoimmune thyroiditis. Women with gonadal dysgenesis (Turner syndrome) have a 15% incidence of thyroiditis by age 40 years.
1. Chronic lymphocytic thyroiditis
Also known as “Hashimoto thyroiditis,” chronic lymphocytic thyroiditis is the most common thyroid disorder in the United States. It is chronic and cell-mediated; T-lymphocyte invasion gives the microscopic appearance of “lymphocytic thyroiditis.” Humoral autoimmunity, with detectable serum antithyroid antibodies (TPO Ab or Tg Ab, or both), is present in most but not all affected patients.
2. Postpartum thyroiditis
Postpartum thyroiditis occurs soon after delivery in about 7% of women. The affected thyroid releases stored thyroid hormone, resulting in transient hyperthyroidism (often mild and undiagnosed) followed by hypothyroidism. The thyroid gland is not acutely tender, but some women complain of mild thyroid discomfort. Most ...