Endocrine Abstracts

Leptin and ghrelin are correlated to acute and chronic nutritional status. Elevated BMI and fat mass as well as food intake increase leptin levels whereas ghrelin levels are reduced. Ghrelin stimulates growth hormone (GH) secretion. The influence of GH on ghrelin is unclear. Since GH reduces fat mass and is dependent on nutritional status we performed this prospective cross sectional study in order to investigate any interaction between GH, ghrelin and leptin levels in active and inactive acromegalic patients (pat).

We measured glucose, insulin, ghrelin, leptin and GH concentration during a 3 h oral glucose tolerance test (OGTT) and IGF-I in 36 acromegalic patientsients (19f/17m, median age 53.3y (20-75)). 29/36 patients underwent surgery. At time point of evaluation none of the patients had received radiotherapy or any medication for acromegaly. Concentration of GH and IGF-I were determined by a single laboratory using the same immunoassay (Nichols Advantage, San Clemente, CA). Active disease was defined as IGF-I above the upper limit of age- and sex-adjusted normal.

11 patients had active acromegaly, 25 were inactive. BMI was not significantly different between active and inactive patients. Baseline ghrelin levels were significantly reduced in active compared to inactive patients (P<0.01), baseline leptin levels were only slightly reduced (p=n.s.). Basal leptin was positively correlated to baseline blood glucose in active patients (P<0.01) and to BMI in inactive patients (P<0.05). During OGTT ghrelin and leptin significantly decreased (active: P<0.01; inactive: P<0.001). The ghrelin decline was significantly higher in inactive patients (P<0.05).

In active acromegalic patients the ghrelin regulation by nutritional status and food intake is reduced which could be due to a negative feedback of GH and IGF-I on ghrelin secretion. The tendency of lower leptin levels in active acromegalic pat might be caused by lipolytic effect of elevated GH levels.