Hyperthyroidism Due to Thyrotropin-Producing Pituitary Chromophobe Adenoma

A 50-year-old man with bitemporal hemianopsia and an enlarged sella turcica was found to have hyperthyroidism with elevated serum thyrotropin levels (17 mμg per milliliter) measured by radioimmunoassay. Craniotomy was performed after the hyperthyroidism had been controlled with antithyroid medication, and a chromophobe adenoma was partially resected. After operation the antithyroid therapy was discontinued. Clinical and laboratory evidence of hyperthyroidism recurred with elevated serum thyrotropin levels (7 to 10 mμg per milliliter). After treatment of the remaining pituitary tumor with external irradiation there was remission of the hyperthyroidism without other antithyroid therapy. The serum thyrotropin levels have subsequently been normal (1.6 to 2.8 mμg per milliliter). The pituitary adenoma appeared to have caused hyperthyroidism by producing excess thyrotropin.