RESUMEN
We present a 49 year old male patient with thyroid stimulating hormone (TSH) producing pituitary macroadenoma. He had been mistakenly diagnosed and treated as Graves' disease for 1 year. Serum TSH level was inappropriately elevated in the presence of high serum total and free thyroid hormone concentrations. Thyrotropin releasing hormone stimulation showed blunt response of TSH but good response for prolactin. The alpha-subunit level and alpha-subunit to TSH molar ratio were measured and found to be high before surgery. The sex hormone-binding globulin level was also high. MRI demonstrated a pituitary macroadenoma. Insulin tolerance test and GnRH revealed normal response. The patient was given a high dose of PTU combined with lugol's solution for controlling hyperthyroidism preoperatively. Transfrontal surgery was performed and the tumor was partially removed. The diagnosis was confirmed by tissue pathology and immunohistochemistry staining of the tumor. The immunohistochemistry staining was performed and found that tumor cells were strongly reactive to TSH with a relatively mild degree for follicular stimulating hormone and leutinizing hormone. The tumor cells were not stained for prolactin, growth hormone and ACTH. Supervoltage irradiation by 60Co was delivered to the pituitary area because of persistence of hyperthyroidism. While waiting for the remote effect of radiotherapy, the patient was given an antithyroid drug to control hyperthyroidism.