Triiodothyronine thyrotoxicosis complicating primary hypothyroidism in a patient with autoimmune thyroiditis.

It is increasingly recognized that autoimmune thyroiditis can have a multifaceted presentation. Documented triiodothyronine thyrotoxicosis developed in a patient with a six-year history of primary hypothyroidism that was left untreated. Serologic and cytologic evidence confirmed the thyroid dysfunction as being on an autoimmune basis. Chronic lymphocytic thyroiditis may be seen with hyperthyroidism, hypothyroidism, or euthyroidism, and in an individual patients, spontaneous progression from one metabolic state to another may occur.