Detection of gonadotropin-releasing hormone receptor in normal human pituitary cells and pituitary adenomas using immunohistochemistry

Gonadotropin-releasing hormone (GnRH), which is a well-known regulator of g onadotroph function, has recently been considered to be a paracrine factor involved in the control of somatotroph, lactotroph, and corticotroph cells. GnRH action is initiated by binding to a specific cell surface receptor, t he gonadotropin-releasing hormone receptor (GnRHR), which is expressed by f ollicle-stimulating hormone/luteinizing hormone (FSH/LH) cells. Using in si tu hybridization techniques, GnRHR messenger ribonucleic acid (mRNA) has re cently been detected in normal human anterior pituitary gland and in variou s pituitary adenomas, including FSH/LH-cell, growth hormone (GH)-cell, adre nocorticotropic hormone (ACTH)-cell, and null-cell adenomas. However, immun ohistochemical studies indicating the specific cell distribution of GnRHR i n normal pituitary cells have never been reported. The aim of the present i nvestigation was to evaluate the immunohistochemical expression of GnRHR in different types of normal pituitary cells and related tumors. Using double -label immunohistochemical techniques on formalin-fixed and paraffin-embedd ed tissues and specific antibodies directed against pituitary hormones and GnRHR, we found GnRHR immunoreactivity not only in FSH/LH cells, but also i n GH- and thyroid-stimulating hormone (TSH) cells. GnRHR was detected in FS H/LH-cell, GH-cell, mixed GH- and prolactin (PRL)-cell, and alpha-subunit ( alpha-SU)/null-cell adenomas. The findings of this study suggest that the i nteraction between GnRH and GnRHR may play a role in paracrine/autocrine re gulation of different types of normal pituitary cells and pituitary adenoma s.