Ghrelin is a newly characterized, widely distributed
peptide thought to be involved in the regulation of appetite. Significant effects on the release of
growth hormone (GH) and
ACTH have been demonstrated. This study compares the expression of
ghrelin and its receptor (GHS-R) in various adrenal
tumors and normal adrenal gland. Normal adrenal tissue was obtained after autopsy. Tissue was obtained from 13
pheochromocytomas (PHEOs), 15
cortisol-secreting
adenomas (CPAs), 12
aldosterone-secreting
adenomas (APAs), and 16 nonfunctional
adenomas (NFAs) following laparoscopic surgery. Expression of
ghrelin and
GHS-R1a was investigated on
RNA levels by using real-time reverse transcription polymerase chain reaction (RT-PCR) and on
protein levels by using immunohistochemistry. In the seven normal adrenal glands analyzed,
ghrelin mRNA levels were 12-fold lower than in stomach.
Ghrelin protein expression was confirmed by immunohistochemistry. In all adrenal
tumors, relevant levels of
ghrelin mRNA were observed, with significantly lower expression in PHEOs and APAs than in normal adrenal gland.
Ghrelin protein was detected in 0% of PHEOs, 55% of APAs, 87% of CPAs, and 54% of NFAs.
GHS-R1a mRNA expression was detectable in normal adrenal gland, but the receptor
protein was absent. In adrenal
tumors, detectable levels of receptor
mRNA were found in 38% of PHEOs, 13% of CPAs, and 25% of NFAs.
GHS-R1a protein was absent in the majority of adrenal
tumors. Expression of
ghrelin in normal adrenal gland and adrenal
tumors may indicate some unknown physiological function. The pathophysiological relevance of
ghrelin expression in adrenal
tumors remains to be investigated.