hormone « Back to Glossary IndexSmall peptides made by cells that regulate the activity of other cells. Related Articles: 14 – 8 The human microbiome16 – 6 Errors of the Immune System27 – 5 More Fungi – Dikaryomycota, rusts, smuts, and yeast28 – 3 α Proteobacteria, Part 27 – 6 How genetic engineering impacts your life« Back to Glossary Index