Endocrine Abstracts

Graves’ disease is characterized by the occurrence of antibodies against thyroid-stimulating hormone (TSH) receptor that stimulate the gland to produce T4 and T3. It can be accompanied by an infiltrative orbitopathy and oftalmopathy. Another seldom- regognized feature of this disease is thymic hyperplasia.

The authors report the case of a 22-year-old woman with Graves’ disease (TSH receptor antibodies 178 U/l) with exuberant oftalmopathy and an incidentally discovered anterior mediastinal mass with no invasive characteristics. She began treatment with a thionamide agent (tiamizol) with great improvement of the thyrotoxic state and concomitant reduction of the thymic mass dimension. This patient was submitted to total thyroidectomy and one year later the thymic mass had totally regressed.

Although thymic hyperplasia is a common and reversible feature in Graves’ disease, in most of the cases thymic enlargement is minimal and a radiologically detectable massive enlargement of the thymus is infrequently reported. The recognition of this association is very important. If the thymic mass radiological characteristics suggest benignity and if it shrinks with Graves’ disease improvement, one should treat Graves’ disease and radiologically watch the mass. This attitude will spare a major surgery – thymectomy.

It has been suggested that the thymus gland has TSH receptors and that might be the pathophysiological explanation for this association.