Perioperative plasma active and total ghrelin levels are reduced in acromegaly when compared with in nonfunctioning pituitary tumours even after normalization of serum GH

Abstract

Ghrelin is a novel gastric peptide known to stimulate GH secretion, but the relationship between ghrelin and the GH-insulin-like growth factor (IGF)-1 axis in GH excess or deficiency is poorly understood. This study investigated dysregulation of ghrelin secretion in acromegaly and its short-term postoperative recovery. A prospective study was conducted on eight patients who underwent complete transsphenoidal resection of GH-producing pituitary adenomas (acromegaly group) and 22 for endocrinologically nonfunctioning pituitary tumours (control group). Active and total plasma ghrelin levels were measured serially before and after surgery. Preoperative active and total plasma ghrelin concentrations (mean +/- SD; fmol/ml) were significantly reduced in acromegalic patients when compared with those in the controls (9.6 +/- 4.3 and 157.4 +/- 65.6 vs. 21.8 +/- 13.0 and 267.1 +/- 111.4; P = 0.023 and P = 0.021, respectively). Both levels were still significantly suppressed on postoperative Day 7 in the acromegaly group when compared with those in the control group (11.7 +/- 4.3 and 197.8 +/- 68.9 vs. 22.5 +/- 12.6 and 302.7 +/- 100.0; P = 0.038 and P = 0.018, respectively). The ratios of active to total ghrelin were not significantly different between the two groups before and after operation. In acromegalic patients, active and total ghrelin levels remained significantly suppressed even after normalization of serum GH levels. The putative negative feedback mechanism of GH on ghrelin secretion may in part account for the low ghrelin levels observed in acromegalic patients, and the mechanism may persist even after normalization of serum GH.