Serum Leptin and Ghrelin Levels in Active and Inactive Acromegalic Patients During an Oral Glucose Tolerance Test

Abstract

Objective: Elevated BMI, fat mass and food intake increases leptin whereas ghrelin is reduced. Ghrelin stimulates growth hormone (GH) secretion. This prospective cross-sectional study was performed to investigate the influence of GH excess on leptin and ghrelin levels at baseline and after glucose load in a large group of acromegalic patients.

Design/Methods: Leptin, ghrelin, GH, glucose and insulin concentrations were measured during a 3 h OGTT in 17 active, 25 inactive patients without medication (inact) and 8 inactive patients treated successfully with somatostatin analogues (inact-SA). Leptin concentration was measured using an in-house immunfluorometric assay, total serum ghrelin by a commercially available radioimmunoassay. Leptin was corrected for BMI.

Results: During OGTT, no significant difference of baseline, nadir or AUC of leptin/BMI was seen between the groups (baseline leptin/BMI: act: 0.26 μgm²/lkg (0.06–0.87); inact: 0.34 μgm²/lkg (0.03–1.79); inact-SA: 0.29 μgm²/lkg (0.03–1.47). A slight but significant reduction of leptin/BMI occurred in all groups during OGTT (active p<0.001, inact p<0.001, inact-SA p<0.05). Inact had higher ghrelin levels (130 ng/L (69–292) compared to active (102 ng/L (27–232); p=n.s.). Inact-SA had significantly lower ghrelin levels (88 ng/L (72–113)) than inact (p<0.001). There was a significant decline of ghrelin during OGTT in all groups (active p<0.001, inact p<0.001, inact-SA p<0.05).

Conclusions: GH only has a slight influence on leptin secretion. Ghrelin levels are lowered by GH and SA. Nevertheless, the physiological decreasing effect of glucose load on ghrelin secretion is preserved.

Key words

pituitary adenoma - hormones - leptin - obesity

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