ABSTRACT
Thyrotropin(TSH)-secreting pituitary adenoma is a rare disorder causing hyperthyroidism, which is one of the syndrome of inappropriate secretion of TSH. It is characterized by high serum T4, T3 as well as elevated serum TSH. Generally serum free alpha-subunit concentration is also increased and alpha- subunit/TSH molar ratio is more than 1. This alpha- subunit/TSH molar ratio is a clue of diagnosis as well as a useful marker of therapeutic response. We experienced a case of 29-years old man with hyperthyroidism due to TSH-secreting pituitary adenoma. He was underwent 1.5cm sized pituitary tumor removal via transsphenoidal approach in our neurosurgery department. In immunohistochemical stain monotonous tumor cells showed strong positive reaction to antihuman TSH antibody and equivocal reaction to ACTH antibody. After operation, goiter size was progressively decreased and also serum T4, T3 and TSH were decreased in nearly normal range. However, he showed elevated serum T4, T3 and TSH after 1 month due to residual tumor. So he received radiation therapy thereafter. In this case the alpha-subunit and alpha-subunit/TSH molar ratio were not increased. So we report a case of TSH-secreting pituitary macroadenoma which had low alpha-subunit/TSH molar ratio with a literature review.