Hormone production in clinically nonfunctioning pituitary adenomas

Abstract

Pituitary tumors in which no excess hormone secretion can be identified clinically have been considered as nonfunctioning or null-cell adenomas. Immunocytochemical data presented here suggest that many of these tumors contain subunits of the glycoprotein hormones. Of 160 patients referred for pituitary surgery, 37 (23%) had no evidence of excess hormone secretion on preoperative endocrine evaluation. Immunocytochemical staining of these tumors was carried out using antibodies specific for prolactin, growth hormone, adrenocorticotropic hormone, the beta subunits of luteinizing hormone (beta-LH), follicle-stimulating hormone (beta-FSH), and thyroid-stimulating hormone (beta-TSH), and the alpha subunit. One or more of these pituitary hormones were detected in 73% of cases. The alpha and beta subunits were detected most frequently, being found in 68% of cases; 27% had staining for one or more beta subunits and 37.9% had staining for both alpha and beta subunits. The incidence was: beta-FSH in 58%, beta-LH in 47%, beta-TSH in 33%, and the alpha subunit in 42%. Staining for multiple glycoprotein hormones was common (52%), and mixed glycoprotein hormones and prolactin cell types were found in 16% of cases. These data suggest that most apparently nonfunctioning pituitary tumors contain immunoreactive hormones and the majority of these are subunits of the glycoprotein hormones. Since the glycoprotein hormone beta subunits must combine with the alpha subunit to produce biologically active hormones, the production of the subunits alone may not have endocrine manifestations.

Defective Expression of Prohormone Convertase 1/3 in Silent Corticotroph Adenoma

“…It has been reported that the incidence of SCA among NFA ranged between 6 to 8.1% [1,10]. The present study showed the higher incidence (20%) of SCA (6 out of 30 NFAs), suggesting that SCA is not so unusual as previously thought.…”

Clinically nonfunctioning pituitary tumors are monoclonal in origin.

“…Light and electron microscopy studies show the presence of secretory granules in neoplastic pituitary tissue (5). RNA anal-ysis (6-9) and immunocytochemistry (10)(11)(12) also confirm the synthesis and secretion of intact gonadotropins or their subunits by a subset of nonfunctioning pituitary adenomas.…”

Relevance of Ki-67 and prognostic factors for recurrence/progression of gonadotropic adenomas after first surgery

“…Gonadotropin-secreting adenomas (GSAs) account for w12-17% of surgically treated pituitary adenomas (1,2). Since GSAs show no signs of endocrine hyperfunction, their clinical characteristics and long-term outcome differ from those of other pituitary adenomas, which frequently involve extrasellar extension with mass effects, visual disturbances, and pituitary dysfunction (3).…”