We read with interest the article by Nwokolo et al reporting raised serum ghrelin levels following Helicobacter pylori eradication (Gut 2003;52:637–40). There are some exceptions to the interpretation of the data that we would take.
The authors state that the increase in ghrelin levels seen in their study “lends support to the view that ghrelin could be involved in the long term regulation of body weight”. While there is growing evidence to support this in the literature,1–3 this study does not present any such data and is not methodologically geared towards addressing this question. The proposal that eradication of H pylori leads to an increase in ghrelin levels, which in turn leads to an increase in obesity, is also without foundation. The only known situation in which hyper-ghrelinaemia is associated with obesity is in Prader-Willi syndrome.4 In all other studies ghrelin levels correlate inversely with measures of body adiposity, and are altered in a compensatory manner by changes in body weight.5 To suggest therefore that H pylori eradication leads to a hyper-ghrelinaemic state that drives increased appetite is not physiologically feasible as any transient appetite increase would be expected to be countered by any increase in adiposity, which in turn would suppress ghrelin levels.
The authors’ proposal that “children with H pylori may have relatively low ghrelin concentrations contributing to growth retardation” is also without foundation. A recent study has shown H pylori status to have no effect on ghrelin levels.6 The role of ghrelin on the growth of children remains unclear. Ghrelin is an endogenous ligand to the growth hormone secretagogue receptor (GHS-R), and potently stimulates growth hormone release. It may indeed have a role to play in growth, as in patients with a genetic growth hormone releasing hormone deficiency nocturnal enhancement of growth hormone secretion remains,7 an effect that may be mediated by ghrelin.
One other proposal of the authors is that H pylori eradication increases 24 hour gastric acidity by a ghrelin dependent mechanism. While central and peripheral ghrelin administration has been shown to increase stomach acidity when given to rats,8 data are lacking in humans. The small but statistically significant increase in acidity seen here would be expected after H pylori eradication, and is likely to be secondary to parietal cell recovery following resolution of inflammation. The suggestion that hypergastrinaemia leads to lower ghrelin levels, and vice versa, is not supported in the literature.9
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