Ghrelin, a novel endogenous
ligand for the GH
secretagogue receptor, has been reported to stimulate GH secretion and food intake in both humans and other animals. Interestingly, recent data indicate that
ghrelin is up- and down-regulated in
anorexia nervosa (AN) and
obesity, which are also known to be accompanied by increased and reduced GH levels respectively. Ageing is associated with a gradual but progressive reduction in GH secretion, and by alterations in appetite and food intake. The role of
ghrelin in the decline of somatotroph function and the
anorexia of ageing is unknown. To investigate the influence of age on circulating levels of
ghrelin, a total of 19 young and old normal weight subjects (Y-NW, n=12; O-NW, n=7), six patients with active AN (A-AN), and seven patients with
morbid obesity (OB) were studied. In addition to fasting plasma
ghrelin concentrations, baseline serum TSH,
IGF-I and
insulin levels were measured. Mean plasma
ghrelin concentrations in A-AN or OB were higher and lower respectively than those present in Y-NW. Interestingly, mean plasma
ghrelin concentrations in O-NW were significantly lower than those present in Y-NW and superimposable on those of OB. The mean fasting plasma
ghrelin concentrations in all groups of subjects were negatively correlated with body mass index and serum
insulin levels, but not with TSH and
IGF-I levels. This study provides evidence of an age-related decline of plasma
ghrelin concentrations, which might explain, at least partially, the somatotroph dysregulation and the
anorexia of the elderly subject.