Postpartum changes in pattern of gastrointestinal regulatory peptides in human milk

Concentrations of gastrointestinal neuropeptides in serial human milk samples from 28 women were determined over the first 6 postpartum mo. All gut neuropeptides were present during the first postpartum week. Gastric inhibitory peptide (GIP) concentration remained constant but the others decreased by 6 wk. Bombesin concentration in breast milk was threefold greater than concurrent plasma concentration (p less than 0.001); all other neuropeptides were at the same or lower concentrations in milk than in plasma. At 36 wk gestation plasma concentrations of GIP were lower and concentrations of vasoactive intestinal peptide were higher than concentrations in age-matched control subjects. Concentrations of gastrin and cholecystokinin, bombesin, peptide histidine methionine, peptide YY, and neurotensin in plasma were similar in pregnant and nonpregnant women. These gut neuropeptides in milk may be important for growth and maturation of the gastrointestinal system in neonates. Bombesin may contribute to neonatal hypergastrinemia.