Prolactin and growth hormone-producing pituitary adenomas. An immunohistochemical and ultrastructural study.

Thirteen prolactin and five growth hormone-producing pituitary adenomas were studied by immunohistochemistry and electron microscopy. The immunohistochemical localization of prolactin and growth hormone correlated well with elevated serum levels of pituitary hormones in all cases. Ultrastructural characterization by granule density and secretory activity was studied in relation to the serum levels of pituitary hormones and the sizes of the tumors. This indicated that markedly elevated serum hormone levels were related to larger tumors with high secretory activity, as indicated by abundant endoplasmic reticulum and well-developed Golgi complexes rather than to the numbers of cytoplasmic granules in the tumors. Two patients with prolactin-producing adenomas had been treated with bromocryptine before surgery. Both tumors showed evidence of degeneration, including cytoplasmic vacuolization. In one case the tumor had an increased number of secretory granules, while in the other case there were few viable cells and an abundance of amyloid deposits. The effects of bromocryptine therapy on pituitary tumor morphology in these two cases include an increased number of pituitary granules, and cellular degenerative changes.