How do pyrogens induce fever through prostaglandin synthesis?

How do pyrogens induce fever through prostaglandin synthesis?

• A. Pyrogens suppress hypothalamic COX enzymes reducing PGE2
• B. Pyrogens stimulate sympathetic nerves directly raising body temperature
• C. Pyrogens stimulate hypothalamic COX enzymes increasing PGE2 synthesis, raising the set point
• D. Pyrogens decrease metabolic rate to conserve heat

Answer: (C)

Fever from pyrogens happens because they trigger the hypothalamus to raise its temperature set point by increasing prostaglandin E2 (PGE2) production. When pyrogens—such as bacterial components or inflammatory cytokines like IL-1, TNF, and IL-6—are detected, they induce COX-2 in the hypothalamus, boosting synthesis of PGE2. The extra PGE2 acts on EP3 receptors in the hypothalamic preoptic area, shifting the thermostat upward. In response, the body activates heat-producing and heat-conserving mechanisms—shivering, nonshivering thermogenesis, and vasoconstriction—to reach the new set point. This is why fever accompanies infection and why drugs that inhibit COX enzymes and reduce PGE2 can lessen fever.

Fever from pyrogens happens because they trigger the hypothalamus to raise its temperature set point by increasing prostaglandin E2 (PGE2) production. When pyrogens—such as bacterial components or inflammatory cytokines like IL-1, TNF, and IL-6—are detected, they induce COX-2 in the hypothalamus, boosting synthesis of PGE2. The extra PGE2 acts on EP3 receptors in the hypothalamic preoptic area, shifting the thermostat upward. In response, the body activates heat-producing and heat-conserving mechanisms—shivering, nonshivering thermogenesis, and vasoconstriction—to reach the new set point. This is why fever accompanies infection and why drugs that inhibit COX enzymes and reduce PGE2 can lessen fever.