orexigenic
That stimulates the appetite.
Ghrelin is a 28‐amino acid acylated peptide predominantly secreted by the stomach but also by the brain. In mammals, ghrelin stimulates both GH [growth hormone] secretion and appetite, and it is the only GI [gastrointestinal] hormone with confirmed orexigenic properties[…].
Where it comes from
From Ancient Greek ὄρεξις (órexis, “appetite”) + -genic.
Adapted from the Wiktionary entry orexigenic (CC BY-SA 4.0).