GROWTH HORMONE-RELEASING HORMONE-RECEPTOR MESSENGER-RNA IN ACROMEGALIC PITUITARY-TUMORS

The growth hormone (GH)-releasing hormone receptor (GHRH-R) has been r ecently cloned and found to be a member of a net, family of seven tran smembrane receptors that includes secretin, vasoactive intestinal pept ide, calcitonin, and corticotropin-releasing factor GHRH-R mRNA has be en demonstrated by Northern blot analyses to be present specifically i n the anterior pituitary gland. To determine the precise cellular loca lization of this receptor in normal anterior pituitary and pituitary a denomas, GHRH-R mRNA was analyzed in 2 normal human pituitary glands a nd 16 human pituitary adenomas using in situ hybridization. GHRH-R run s specifically localized in somatotroph cells in the normal pituitary. In the adenomas, all GH-producing adenomas originating from acromegal ic patients demonstrated up-regulation of GHRH-R mRNA when compared wi th levels in the normal pituitary. Only one of fire clinically nonfunc tioning adenomas, a gonadotroph luteinizing hormone/follicle-stimulati ng hormone-positive adenoma, exhibited up-regulation of this receptor message, Adrenocorticotrophic hormone-secreting and prolactin-secretin g adenomas did not express GHRH-R message. In summary, GHRH-R is speci fically expressed in somatotrophs and GH-producing adenomas, suggestin g that GHRH-R may influence GH release in adenomas similar to this rec eptor's actions ill the normal somatotrophs and may be involved in the growth of GH-secreting adenomas.