Three classes of Hormones

There are three major classes of hormones. Peptide hormones are small protein molecules. Their mechanism of action is binding to G-protein coupled receptors for fast effects. An example of an amine is acetylcholine. Amines are modified amino acids. Their mechanism of action is the same as peptides. Common amines include epinephrine and norepinephrine. Steroids are derivatives of cholesterol. Their mechanism of action includes diffusing across the cell membrane and binding to cytosolic receptors. They affect gene expression by contributing to chromatin remodeling. Cortisol is a well known steroid that regulates glucose levels and promotes learning during stressful situations.