Peptide hormones are small proteins made up of chains of amino acids. They are produced by various glands in the body, such as the pituitary gland and pancreas, and play crucial roles in regulating physiological processes. Examples include insulin, which helps control blood sugar levels, and growth hormone, which influences growth and metabolism. These hormones work by binding to specific receptors on target cells, triggering a response that can affect metabolism, growth, and mood. Unlike steroid hormones, which are derived from cholesterol, peptide hormones are water-soluble and cannot easily pass through cell membranes, requiring receptor-mediated signaling to exert their effects.