Ghrelin immunoreactivity (green fluorescence) is detected in both the pancreas and stomach of P10 mouse pups (A, B). Postnatal stomach ghrelin expression increases gradually to reach adult-like levels by 3–5 weeks of life (A). Meanwhile, pancreatic ghrelin expression declines progressively and is barely detectable in the adult pancreas (B). See Supplemental Online Material for detailed methods. Instead of regulating food intake, perinatal ghrelin appears to be an important signal for the growth and development of various tissues, including the pancreas, gastrointestinal tract, and central nervous system (C).