[Autoimmune thyroid diseases complicated with reversible changes of thyroid function]

Autoimmune thyroid disease (AID) with reversible thyroid dysfunction was classified mainly by etiology. Hashimoto thyroiditis itself, pregnancy, cytokine therapy and various drugs, iodine-rich food and AID with TSH receptor antibody (TRAb) were main items. Silent or painless thyroiditis which was termed destructive thyroiditis occurs without clear cause or after adrenectomy for Cushing syndrome. Abnormal human chorionic gonadotropin (hCG) rarely causes transient thyrotoxicosis at early phase of pregnancy and postpartum thyroiditis which has similar symptom as silent thyroiditis is relatively common disorders. Thyroid dysfunction of patients with both TRAb (TSAb and TSBAb) is pathophysiologically unknown and the detection of both antibodies in a patient serum is difficult methodologically. We developed the highly sensitive TSAb assay by patients' IgG precipitated by high concentration PEG (22.5%) using porcine thyroid cell. This assay is also useful for detection of the coexistence cases of TSAb and TSBAb.