With the use of an anti-human S-100 protein antibody, it was possible to reveal a characteristic cell type in the anterior lobe of the normal human pituitary. These cells, so-called folliculo-stellate cells, were present in all pituitaries studied but their number varied from one gland to another. Immunoreactive cells, isolated or grouped, were arranged close to various secretory granulated cells. Especially by use of double immunoenzymatic labeling, it was evident that these cells are spatially related either to somatotropes, prolactin cells and "corticotropes", or to glycoprotein-containing cells. Such immunoreactive cells were rare or absent in pseudo-follicular arrangements of secretory granulated cells. Since it is now possible to identify this cell type by light microscopy and since no reliable functional significance is known, it seems more advisable to term this cell type "stellate cell" instead of "folliculo-stellate cell".

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This report describes the histologic, immunocytochemical, and ultrastructural study of a multihormonal carcinoid tumor of the pancreas, secreting a growth hormone releasing factor (GRF) which provoked acromegaly. The patient presented a nonfamilial multiple endocrine neoplasia, type 1. The absence of radiologic signs of a pituitary adenoma in conjunction with elevated plasma levels of pancreatic polypeptide, glucagon, somatostatin, as well as growth hormone (GH), led to the discovery of the tumor. Its surgical excision produced a rapid disappearance of most of the clinical and biologic disorders. No immunoreactive GH was found in the tumor using radioimmunoassay and immunocyto‐chemistry. In contrast, three peptides with GH‐releasing activity were extracted and characterized. Immunocytochemistry showed that the GRF‐reactive cells, together with rare somatostatin‐storing cells, made up areas which demonstrated a medullary pattern of growth with extracellular amyloid deposits. Under electron microscopic examination, actively secreting cells were observed which carried endocrine granules of 100 to 150 nm in diameter. The other regions of the tumor presented a different type of growth and were composed of pancreatic polypeptide‐, glucagon‐, or somatostatin‐reacting cells. Cells immunostained with antisera raised against β‐endorphin were also noted. These data suggest that GRF may be a new biologic marker for pancreatic endocrine tumors.

In two of eight premenopausal women with somatotropic adenomas, galactorrhea was the earliest clinical feature, associated in one patient with amenorrhea. These two patients did not have clinically evident acromegaly. Mean basal serum GH levels were elevated and did not decrease after glucose ingestion. Both patients had modest hyperprolactinemia. Histological and immunocytological studies of the adenomas showed numerous adenomatous somatotropic cells and some alpha-subunit- and PRL-containing cells. In these patients, the origin of the hyperprolactinemia was not clear. In one patient, elevated GH secretion was probably responsible for the galactorrhea, since it disappeared after surgical treatment despite persistence of hyperprolactinemia. In conclusion, galactorrhea, isolated or associated with amenorrhea, can be the only clinical manifestation of a somatotropic adenoma.