Endocrine Abstracts

In GH deficiency (GHD), fat mass is elevated compared to normal subjects. Leptin is positively related to fat mass, BMI and food intake, while ghrelin correlates negatively. During an oral glucose tolerance test (OGTT), leptin increases in obese subjects and generally does not change in normal weight subjects. Ghrelin decreases during OGTT. We performed a cross-sectional study in order to investigate the influence of GH-substitution on leptin and ghrelin in GHD.

Ghrelin and leptin were measured during 3 h OGTT in 52 GHD (21f/31m, median age 51.5 years (range 27–82)). Twenty-two GHD were on GH substitution (GH-sub) for a median of 10 years (2–42). Thirty patients were not substituted for at least 2 years (non-sub). Leptin was measured using an immunfluorometric in-house assay, total serum ghrelin by a radioimmunoassay (Phoenix Pharmaceuticals, USA). Body composition was measured by dual-energy-X-ray-absorptiometry.

Age and BMI (GH-sub 26 kg/m² (21–42) versus non-sub 29 kg/m² (22–66)) were not significantly different between GHD groups. Fat mass was significantly higher in non-sub (37% (20–52) vs 31% (13–54), P<0.01), so were basal leptin (16 μg/l (3.3–89) vs 7.5 μg/l (0.5–130), P<0.05) and the area-under-the-curve (AUC) of leptin (P<0.05). Baseline ghrelin (GH-sub 145 ng/l (83–280) vs 113 ng/l (61–270)) and AUC of ghrelin were slightly but not significantly lower for non-sub compared to GH-sub. Leptin and ghrelin decreased significantly after glucose (maximum at 60 min) in both groups (P<0.001). The lower fat mass of GH-sub caused by lipolytic GH might lead to lower leptin levels. The reason for decreasing leptin levels during OGTT in both groups remains unclear. Ghrelin levels were not significantly different between groups possibly due to the counterbalance between the suppressive effect of GH and the stimulating effect of reduced fat mass. GH has no effect on ghrelin regulation during OGTT.