Expression of ghrelin and its receptor (GHS-R1a) in adrenal tumors and normal adrenal gland

Ghrelin is a newly characterized peptide thought to be involved in the regulation of appetite. Furthermore, significant effects on the release of growth hormone (GH) and ACTH were demonstrated. We investigated expression of ghrelin and GHS-R type 1a mRNA in various adrenal tumors and in normal adrenal gland. Tissue from 15 pheochromocytomas (PHEO), 15 Cushing’s adenomas (CUSH), 12 Conn’s adenomas (CONN) and 15 non-functional adenomas (NFA) was obtained following laparoscopic surgery. Total RNA was extracted and the absence of genomic DNA contamination was confirmed by RT-PCR/ PCR amplification of ß2-microglobulin. Ghrelin and GHS-R1a mRNA levels were investigated using real-time RT-PCR. In normal adrenal gland, significant levels of ghrelin mRNA were observed. Stomach total RNA, which was used as positive control, demonstrated 60-fold higher level than normal adrenal gland. Furthermore, significant levels of ghrelin mRNA were observed in all tumors without any differences between the various entities. Expression levels ranged form comparable levels to a hundredth of the levels observed in normal adrenal gland.

Similar to ghrelin itself, significant expression of GHS-R1a was demonstrated in the normal adrenal gland. A GH-secreting pituitary adenoma, used as a positive control, demonstrated 300-fold higher levels. In adrenal tumors, relevant levels of receptor mRNA were found in 33% of PHEO, in 13% of CUSH, in 0% of CONN and in 13% of NFA analyzed.

In conclusion, ghrelin expression may indicate some function as an intraadrenal regulator. Alternatively, expression of ghrelin may point to some function of the adrenal gland in the regulation of appetite.