Objective: 

Ghrelin is a novel growth hormone (GH) releaser acylated peptide that has recently been purified from stomach, and which potently binds to the GH secretagogue receptor.

In rats, fasting leads to elevated serum GH concentrations. Age-related decreases in energy expenditure have been associated with the loss of skeletal muscle and decline of food intake, possibly through a mechanism involving changes of growth hormone (GH) secretion and feeding behavior. Ghrelin releases GH in vitro and in vivo in animal models, however its actions, potency and specificity in humans are unknown.

Methods: 

Here, we investigate the relationship between age-related decline of growth hormone secretion and/or food intake and ghrelin function. Ghrelin (10 nmol/kg body weight) was administered intravenously to male 3-, 12-, 24-and 27-month-old Wistar adult rats, after which growth hormone concentrations and 2 h food intake were measured.

Results: 

An intravenous administration of ghrelin to rats increased food intake in all generations. In addition, to orexigenic effect by ghrelin, intravenous administration of ghrelin elicited a marked increase in plasma GH levels, with the peak occurring 15 min after administration.

Conclusions: 

These changes in serum ghrelin concentrations during fasting were followed by similar, profound changes in serum GH levels These datas indicate that ghrelin is the main driving force behind the enhanced GH secretion during fasting.