Pituitary adenoma producing thyrotropin and prolactin. An immunocytochemical and electron microscopic study.

A pituitary adenoma with suprasellar extension that had caused hyperthyroidism due to secretion of excess thyrotropin (TSH), as well as mild hyperprolactinemia, was studied with differential staining, immunocytochemistry and electron microscopy. Most cells of the tumor strained lightly with aldehyde thionin, which demonstrates the granules of normal thyrotrops, and immunocytochemically with antiserum to the hormone-specific beta chain of TSH. A minority of the cells was immunoreactive for prolactin. Electron microscopy revealed light cells interspersed with highly pleomorphic dark cells. Both were sometimes multinucleated, and contained variable numbers of small secretion granules, multiple Golgi complexes, and abundant endoplasmic reticulum.