Clinical, laboratory, and scintigraphic manifestations of subacute and chronic thyroiditis.

The term "thyroiditis" refers to several syndromes of differing etiology. Chronic or Hashimoto's thyroiditis (HT), an autoimmune disorder that is manifested by goiter and hypothyroidism, is by far the most common of these syndromes. Subacute thyroiditis (SAT) encompasses two distinct syndromes: subacute granulomatous thyroiditis (SAGT) and subacute lymphocytic thyroiditis (SLT). SAGT is viral in origin and usually presents with neck tenderness and hyperthyroid symptoms, while SLT, which is likely to be an autoimmune entity, results in goiter and transient hyperthyroidism. SLT is often seen in the postpartum period and is referred to as postpartum thyroiditis (PPT). Less common forms of thyroiditis include Riedel's struma, which is characterized by extensive fibrosis of the thyroid gland, and acute suppurative thyroiditis, which is a bacterial infection. Twenty patients with goiter were evaluated by thyroid scintigraphy. They were ultimately diagnosed as having either HT (14), SAGT (3), SLT (1), or PPT (2). Their scan findings were correlated with both clinical presentations as well as in vitro laboratory analysis.