Polypeptide hormones that stimulate and sustain the proliferation of epidermal cells. Synthesised by several glands and organs in the body, they have beneficial effects on the intestinal lining and on epithelial turnover. Those present in human milk are thought to support the infant gut. Human milk contains EGF at levels far exceeding bovine milk, and the peptide survives partial digestion to act on the neonatal intestine, promoting mucosal growth and repair. Infant-formula manufacturers study whether adding such bioactive peptides could narrow the functional gap between formula and breast milk, though regulatory and safety hurdles remain.