This module explores the endocrine system as an interconnected communication network linking the brain, glands, immune system, gut, liver, kidneys, adipose tissue, muscle, and bone. It covers the roles of the hypothalamus and pituitary, organ-specific hormonal interactions, metabolic and reproductive axes, and dynamic hormone activation, inactivation, and clearance. The module also focuses on clinical interpretation of thyroid, adrenal, reproductive, and metabolic markers through integrated assessment of laboratory values, symptoms, physiology, and patient context.