Stress Response Counterregulatory Hormones

During fasting or falling blood glucose, the body protects the brain by reducing insulin secretion first. Glucagon rises next, followed by epinephrine and norepinephrine. Cortisol and growth hormone act later and more slowly. This sequence matters: cortisol is not the immediate rescue hormone for hypoglycemia, but it helps sustain glucose availability when stress persists. Acute illness uses the same system at a larger scale. Trauma, burns, sepsis, surgery, and severe pain activate the sympathoadrenal system and the hypothalamic-pituitary-adrenal axis. ACTH stimulates cortisol production, while catecholamines, glucagon, and growth hormone increase. Together, these hormones oppose insulin by: - increasing hepatic glycogenolysis and gluconeogenesis; - mobilizing free fatty acids and amino acids for energy production; - reducing peripheral glucose uptake; and - preserving circulating glucose for vital organs. This response is initially protective. A critically ill patient needs readily available fuel for the brain, myocardium, immune system, and respiratory muscles. The cost is insulin resistance, hyperglycemia, protein breakdown, and muscle wasting when the response is prolonged. Inflammatory cytokines amplify this process. A patient without known diabetes can therefore develop marked hyperglycemia during...