corticosteroid
Summary
Corticosteroids are steroid hormones (glucocorticoids and mineralocorticoids) produced by the adrenal cortex or synthesized as drugs, used for anti-inflammatory, immunosuppressive, and metabolic effects. They act via intracellular receptors to alter gene transcription, affecting glucose metabolism, immune function, and electrolyte balance. Common examples include prednisone, dexamethasone, hydrocortisone, and fludrocortisone.
Detail
Corticosteroids are classified into glucocorticoids (e.g., cortisol, prednisone, dexamethasone) and mineralocorticoids (e.g., aldosterone, fludrocortisone). They diffuse across cell membranes and bind cytoplasmic glucocorticoid or mineralocorticoid receptors, translocating to the nucleus to modulate gene expression—upregulating anti-inflammatory proteins (e.g., lipocortin-1/annexin A1, which inhibits phospholipase A2) and downregulating pro-inflammatory cytokines (IL-1, IL-2, IL-6, TNF-α), COX-2, and adhesion molecules. This suppresses both innate and adaptive immunity, reduces capillary permeability, and inhibits leukocyte migration.
Clinical uses: autoimmune diseases (lupus, rheumatoid arthritis), asthma/COPD exacerbations, allergic reactions/anaphylaxis, transplant rejection prophylaxis, adrenal insufficiency replacement (hydrocortisone/fludrocortisone in Addison disease), inflammatory bowel disease, and cerebral edema (dexamethasone). Also used to accelerate fetal lung maturity (betamethasone) in preterm labor by inducing surfactant production.
Adverse effects reflect glucocorticoid and mineralocorticoid activity: Cushingoid features (moon facies, buffalo hump, central obesity, striae), hyperglycemia, osteoporosis/avascular necrosis, hypertension, peptic ulcers, cataracts, glaucoma, psychiatric disturbances, impaired wound healing, increased infection risk, adrenal suppression (HPA axis suppression requiring tapering), and growth retardation in children. Mnemonic: "CUSHINGOID" for Cushing syndrome features.
Key pharmacology points for boards: potency and mineralocorticoid activity vary by agent (hydrocortisone has significant mineralocorticoid effect; dexamethasone has minimal mineralocorticoid activity but high glucocorticoid potency, useful for dexamethasone suppression test in Cushing syndrome workup). Chronic use requires gradual tapering to avoid acute adrenal insufficiency due to HPA axis suppression. Corticosteroids inhibit phospholipase A2, distinguishing their broader anti-inflammatory mechanism from NSAIDs, which only inhibit COX enzymes downstream.
Sources
- First Aid for the USMLE Step 1
- Katzung's Basic and Clinical Pharmacology
- Goodman & Gilman's The Pharmacological Basis of Therapeutics
- Robbins Basic Pathology
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