Hyperthyroidism Caused by an Ectopic TSH-Secreting Pituitary Tumor

A woman developed what appeared to be typical Graves' disease in 1965 at the age of 45 years. After 9 years of antithyroid drug therapy, she was treated with radioiodine. Ten years later (1985) she developed postablative hypothyroidism. Despite replacement doses of thyroxine that resulted in thyroid hormone levels that were in the hyperthyroid range, TSH levels remained elevated. Initial biochemical studies, including a high alpha-subunit to TSH ratio, suggested a pituitary TSH-secreting tumor, but a CT scan of the sella turcica was normal. In 1994, while undergoing an otolaryngologic examination, the patient was found to have a nasopharyngeal mass lesion, which was ultimately shown histologically and immunohistochemically to be an ectopic pituitary tumor. Resection of the mass restored TSH and alpha-subunit levels to normal. This patient probably represents the first ectopic TSH-secreting pituitary tumor to be reported.