Different effects of short- and long-term recombinant hGH administration on ghrelin and adiponectin levels in GH-deficient adults

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Abstract

OBJECTIVE

To evaluate circulating levels of ghrelin and adiponectin (ApN) in GH-deficient (GHD) adults before and after short- and long-term recombinant human GH (rhGH) administration.

PATIENTS AND METHODS

Twenty-three patients were studied. Seventeen subjects (Group A, 12 men, five women) were evaluated at baseline and after 1 year rhGH therapy (dose mean ± SD: 0·3 ± 0·1 mg/day) with the assessment of serum IGF-I, ghrelin, ApN, leptin, insulin and glucose levels, percentage of body fat (BF%), HOMA-IR and QUICKI. Seventeen age-, sex- and body mass index (BMI)-matched healthy subjects were recruited for comparisons. Six patients (Group B, three men, three women) underwent IGF-I generation test (rhGH 0·025 mg/kg/day for 7 days), blood sampled at baseline and on day 8 for determination of IGF-I, ghrelin and ApN levels.

RESULTS

Group A: at baseline GHD patients showed low IGF-I levels and BF% significantly higher than controls (31·4 ± 2·5 vs. 26·4 ± 1·3, P < 0·05). Glucose, insulin, leptin, tryglicerides, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol levels, as well as HOMA-IR and QUICKI values were similar in the two series, while total cholesterol levels were higher in GHD. In GHD, ghrelin levels were significantly lower than in controls (193·9 ± 27·1 vs. 298·1 ± 32·5 pmol/l, respectively, P = 0·02), while ApN levels were similar (10·2 ± 1·1 and 9 ± 1 mg/l, respectively, P = ns). After 1 year of rhGH therapy, BF%, BMI, serum total and LDL cholesterol significantly decreased, serum leptin levels showed a trend to decrease, while HOMA-IR and QUICKI did not change. Ghrelin and ApN levels significantly increased from 193·9 ± 27·1 to 232·4 ± 26·3 pmol/l (P < 0·01) and from 8·6 ± 0·8 to 10·3 ± 1·1 mg/l (P < 0·05), respectively. In group B, the expected increase in IGF-I levels was associated with a significant decrease in ghrelin levels, while ApN did not change.

CONCLUSION

GHD patients showed serum ghrelin lower than controls, probably due to the higher BF%. No difference in ApN was observed. Ghrelin and ApN increments induced by long-term treatment may be related to the significant BMI and BF% reduction that is the predominant metabolic effect of rhGH therapy. Conversely, the decrease in ghrelin levels observed after short-term rhGH administration may be consistent with an inhibitory feedback of GH and/or IGF-I on ghrelin release.

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