Transient Painless Thyroiditis with Hyperthyroidism: A Variant of Lymphocytic Thyroiditis?*

WITHIN the past decade and particularly within the past 5 years, an unusual form of hyperthyroidism has received increasing attention (1–22). The hyperthyroid manifestations are generally self limiting, although some cases relapse, are accompanied by chronic inflammatory changes within the thyroid parenchyma, and are marked by a very low 131I uptake. Despite the usually abrupt onset of symptoms and the diffuse lymphocytic infiltration, thyroidal pain and/or tenderness is completely absent. Because this syndrome overlaps many of the features of both lymphocytic thyroiditis and subacute thyroiditis, there has been much debate about how to categorize it or whether to consider it a new disease entity. Nomenclature used by the several groups describing it includes: painless thyroiditis (7, 11, 17, 20), silent thyroiditis (3, 9, 19, 22), occult subacute thyroiditis (1), painless subacute thyroiditis (10, 14), subacute nonsuppurative thyroiditis (2), atypical (“silent”) subacute thyroiditis (16), lymphocytic thyroiditis with spontaneously resolving hyperthyroidism (22), hyperthyroiditis (6), lymphocytic thyroiditis (4, 18) and autoimmune disease and thyroiditis (12). The current review was undertaken, therefore, because of this confusion and because of the newly emerging clinical importance of this syndrome. It will focus on the manifestations of this self-limited form of hyperthyroidism and will try to place it into perspective with the more conventional forms of thyrotoxicosis. Although far from clear cut, the data supporting a possible immunological basis will be discussed.