Hormone Metabolism Introduction: Hormone metabolism describes how chemical messengers are made, transported, activated, and cleared to regulate energy use, growth, and internal balance. This article explains the main chemical classes of hormones, how peptide, steroid, and amino-acid-derived hormones are synthesized, and why most circulate bound to plasma proteins with very different half-lives. It outlines core metabolic regulators, insulin and glucagon for blood glucose, thyroid hormones T3 and T4 for basal metabolic rate, and cortisol for glucose production, protein breakdown, and fat redistribution, and shows how negative feedback loops keep their levels within narrow ranges. It also covers peripheral activation steps, including deiodinase conversion of T4 to T3 and the role of selenium-dependent enzymes . How Hormones Are Made, Classified, and Carried Hormones are grouped by chemistry, which determines how they are made and how they travel. ...