Thyroid amyloidosis with recurrent subacute thyroiditis-like syndrome.

We studied 2 men with a subacute thyroiditis-like syndrome (STLS) associated with systemic amyloidosis. Both had very tender, diffuse, firm goiters, low thyroidal radioactive iodine uptake values, and increased erythrocyte sedimentation rates. Glucocorticoid therapy resulted in dramatic improvement. Compared to 18 patients with subacute thyroiditis, these 2 men had 1) persistence of goiter even in remission, 2) repeated exacerbation of STLS, 3) pain always localized in the same site, and 4) gastrointestinal, renal, and cardiac abnormalities. Histological examination of the patients' thyroid glands revealed amyloid deposition and no evidence of subacute thyroiditis. In addition, 1 man had low T3 thyrotoxicosis with an elevated rT3/T3 ratio, suggesting impaired peripheral conversion of T4 to T3, and immunological and histological evidence of Hashimoto's thyroiditis. These findings suggest that thyroid amyloidosis may be associated with STLS. When patients with clinical features of subacute thyroiditis have an unusual course, the possibility of thyroid amyloidosis should be considered.