Ghrelin capacity for food but also dramatically lowers ghrelin levels compared to both lean controls and those that lost weight through dieting alone. However, studies are conflicting as to whether or not ghrelin levels return to nearly normal with gastric bypass patients in the long term after weight loss has stabilized. Bariatric surgeries involving vertical-sleeve gastrectomy reduce plasma ghrelin levels by about 60% in the long term. Ghrelin plasma concentration increases with age and this may contribute to the tendency for weight gain as people age. Ghrelin Ghrelin (pronounced ), the "hunger hormone", also known as lenomorelin (INN), is a peptide
Ghrelin express the ghrelin receptor. The entire ghrelin system (dAG, AG, GHS-R and GOAT) has a gluco-regulatory action. The hippocampus plays a significant role in neurotrophy: the cognitive adaptation to changing environments and the process of learning and it is a potent stimulator of growth hormone. Animal models indicate that ghrelin may enter the hippocampus from the bloodstream, altering nerve-cell connections, and so altering learning and memory. It is suggested that learning may be best during the day and when the stomach is empty, since ghrelin levels are higher at these times. A similar effect on human memory performance is possible.