Regulation of energy balance: In both rodents and humans, ghrelin functions to increase hunger though its action on hypothalamic feeding centers. This makes sense relative to increasing plasma ghrelin concentrations observed during fasting (see below). Additionally, humans injected with ghrelin reported sensations of intense hunger. Ghrelin also appears to suppress fat utilization in adipose tissue
, which is somewhat paradoxical considering that growth hormone has the opposite effect. Overall, ghrelin seems to be one of several hormonal signals that communicates the state of energy balance in the body to the brain.