Abstract
A 23-year-old man of high stature, with hypogonadism and bitemporal-upperquadrantic visual defects was found to have a pituitary tumor. He had a slightly enlarged struma, while he did not show any signs of hyperthyroidism. His serum TSH level (10.4 μU/ml) was slightly elevated in spite of increased levels of serum thyroid hormone (T3 249 ng/dl, T4 12.0 μg/dl). Neither the elevated serum TSH levels nor thyroidal uptake of 123I were suppressed after 7 days of 75 μg triiodothyronine administration. Serum TSH levels did not increase further after TRH administration. Hypofunction of the anterior pituitary gland was observed. Following transsphenoidal hypophysectomy, his serum thyroid hormone and TSH levels returned to the normal range. Immunohistochemical examination revealed the existence of numerous TSH positive cells. From these data we concluded that the patient had a pituitary tumor which secreted inappropriate amounts of TSH.
