Growth hormone-producing pituitary adenoma with crystal-like amyloid immunohistochemically positive for growth hormone.

Growth hormone (GH)-producing pituitary adenoma from a 50-year-old acromegalic female was studied histochemically, immunohistochemically and electron microscopically. The adenoma was characterized by numerous crystal-like amyloid bodies of 5 to 40 micron in diameter. In the periphery of the crystal-like amyloid, bundles of amyloid fibrils were closely associated with deep invaginations of adenoma cells. The adenoma cells had numerous vesicles and vacuoles filled with amyloid fibrils, some of which were continuous with extracellular space. The crystal-like amyloids, as well as the adenoma cells, were immunohistochemically positive for GH. It might be possible that disorder of hydrolysis of "prohormone," from which GH is elaborated, is responsible for the amyloid production, and that amyloid discharge is accompanied with immunoreactive GH.