Single case report: 100 μg Ghrelin at 22: 00 increases distinctly hunger, food intake and nocturnal plasma levels of GH, ACTH and cortisol in a young man – evidence for dose dependent effects of ghrelin on appetite?

Ghrelin, the endogenous ligand of the GH secretagogue receptor, stimulates GH release, appetite and weight gain in humans and rodents. It plays a key role in the regulation of energy balance. After 4×50 μg ghrelin from 22h–1h normal young man reported no change in appetite and no hunger signals. However, a recent study revealed a stimulation of appetite and imagination of food in normal controls after ghrelin at 9h. We report on a 31-year old healthy man, who received a bolus of ghrelin 100 μg at 22h. Immediately after administration he reported a distinct increase in hunger and appetite associated with nausea, shivering and cold sweating. After food intake all symptoms improved. Nocturnal cortisol, ACTH and GH secretion increased. Sleep EEG analysis showed a shortened sleep latency and an increase in sleep stadium IV, besides a sleep disruption, an increase in awakenings and a decrease in REM sleep. Our finding supports the view that ghrelin is a sleep promoting substance and stimulates the nocturnal secretion of GH, ACTH and cortisol. Regarding the effects of ghrelin on stimulation of appetite and food intake, it is remarkable that 100 μg of ghrelin at 22h enhanced, in a similar fashion as ghrelin administered at 09h, in a distinct way appetite and food intake. However, 4×50 μg ghrelin between 22h and 01h showed no behavioral effects. It could be supposed that effects of ghrelin on appetite stimulation and food intake in humans are dose dependent.