Corticosteroids inhibit _______ to decrease synthesis of prostaglandins
**Core Concept:** Corticosteroids are a class of hormones that have anti-inflammatory and immunosuppressive effects. Prostaglandins are a group of lipid compounds that play a crucial role in inflammation, pain, and fever regulation. Corticosteroids inhibit the enzymes involved in prostaglandin synthesis to exert their therapeutic effects.
**Why the Correct Answer is Right:** Corticosteroids inhibit the enzyme cyclooxygenase (COX), which is involved in the conversion of arachidonic acid to prostaglandin H2 (PGH2). PGH2 further undergoes two isomerase reactions to form various prostaglandins, including the potent inflammatory prostaglandin E2 (PGE2) and the mediator of fever, prostaglandin I2 (PGI2). By inhibiting COX enzymes, corticosteroids decrease the synthesis of prostaglandins and reduce inflammation, pain, and fever.
**Why Each Wrong Option is Incorrect:**
A. COX-2 selective inhibitors (e.g., ibuprofen) only target COX-2 enzyme, which is involved in inflammation. They do not reduce the production of PGI2, leading to less anti-inflammatory effect.
B. COX-1 selective inhibitors (e.g., aspirin) only target COX-1 enzyme, which is involved in platelet aggregation and gastrointestinal protection. They do not reduce the production of PGI2, making them less effective in reducing inflammation.
C. COX inhibitors (e.g., naproxen) target both COX-1 and COX-2 enzymes, but still do not reduce PGI2 production, resulting in less effective anti-inflammatory action compared to corticosteroids.
D. Selective COX-1 inhibitors (e.g., omeprazole) only target COX-1 enzyme involved in platelet aggregation and gastrointestinal protection. These inhibitors do not reduce PGI2 production, leading to less anti-inflammatory effect compared to corticosteroids.
**Clinical Pearl:** Corticosteroids are more potent anti-inflammatory agents due to their ability to inhibit both COX enzymes (COX-1 and COX-2) and reduce PGI2 production. This results in a broader range of anti-inflammatory effects and makes corticosteroids superior to selective COX inhibitors in treating inflammatory conditions.