Growth hormone secretagogue receptor expression in human pituitary tumors

The GH secretagogue (GHS) receptor (GHS-R) has been characterized and clone d. It is a member of a family of seven transmembrane receptors and is close ly related to the neurotensin and TRH receptors. To determine the expressio n of this receptor in normal anterior pituitary and in 24 human pituitary a denomas, we analyzed GHS-R messenger ribonucleic acid (mRNA) using a RT-PCR assay. We found that normal human pituitary was positive for the GHS-R sig nal. In addition, all GH-secreting adenomas and the one TSH-secreting adeno ma demonstrated the presence of GHS-R mRNA. Three of four ACTH-secreting tu mors and three of nine gonadotroph adenomas were also positive for the GHS- R mRNA. To determine the amounts of GHS-R mRNA in normal pituitary and in r epresentative tumors, semiquantitative competitive PCR was performed. We de termined that normal pituitary had approximately 750 molecules/L GHS-R mRNA . The acromegalic tumor had approximately 1.5 x 10(5) molecules/L, and the TSH-secreting tumor had approximately 7.5 x 10(3) molecules/L. Other tumor types contained considerably less, with the ACTH-secreting and gonadotroph tumors expressing 7.5 x 10(2) and 3 x 10(2) GHS-R mRNA molecules/L, respect ively. These results suggest that GH- and TSH-producing adenomas express GH S-R mRNA at levels 200 and 10 times higher, respectively, than the normal p ituitary, and that this receptor expression may be involved in the pathogen esis and growth of these pituitary adenomas.