Endocrine Abstracts

Introduction

Graves’ disease is typically characterized by the presence of circulating autoantibodies that stimulate the TSH receptor, inducing hyperthyroidism and goiter. Hashimoto’s thyroiditis is an autoimmune disease leading to thyroid tissue destruction by cell and antibody-mediated immune processes. The development of Hashimoto’s thyroiditis following Graves’ disease is rarely reported. Its pathogenesis is not confirmed. Herein, we report a case of Hashimoto’s thyroiditis following Graves’disease treated with radioactive iodine.

Observation

A 40-year-old woman was referred to our department for thyrotoxicosis. She presented with a weight loss, palpitations, excessive sweating, tremor, and nervousness. On physical examination, she had a regular pulse of 112 beats/mn, a diffusely enlarged thyroid gland, and a tremor in both hands. Laboratory tests revealed overt hyperthyroidism with free thyroxine (FT4) level of 6 ng/ml (normal range: 0.7-1.48) and thyroid stimulating hormone (TSH) level of 0.001 µIU/ml (normal range: 0.35-4.94). Thyroid scintigraphy showed an enlarged gland with diffusely increased tracer uptake, confirming the diagnosis of Graves’s disease. The patient was treated with propranolol and thiamazole. Two months later, she received a radioactive iodine therapy. Three years and 9 months later, the patient had a TSH level of 8.787 µIU/ml with a very high level of thyroperoxydase antibodies (2208 IU/ml; nr: < 35 IU/ml) consisting with the diagnosis of Hashimoto’s thyroiditis. She was treated with levothyroxine.

Discussion and conclusion

In the early stage of Hashimoto’ thyroiditis, a mild and transitory hyperthyroidism may occur as a result of thyroid cells destruction and the releasing of thyroid hormones into circulation. In our patient, based on the severity of hyperthyroidism and the scintigraphic feature, we concluded that the etiology of the initial thyrotoxicosis was Graves’ disease. The occurrence of hypothyroidism could be secondary to radioiodine therapy. However, the very high level of thyroperoxydase antibodies is consisting with the diagnosis of Hashimoto’ thyroiditis. In 10 to 15%of Graves’ disease, Hashimoto’s thyroiditis may occur after remission. The precise mechanisms are not known.