Which enzyme activity is increased in the hypothalamus to raise fever set point?

Which enzyme activity is increased in the hypothalamus to raise fever set point?

• A. Lipoxygenase
• B. Phospholipase A2
• C. Cyclooxygenase
• D. HMG-CoA reductase

Answer: (C)

Fever is driven by increased prostaglandin E2 production in the hypothalamus. When pyrogens stimulate the immune response, cyclooxygenase—especially the inducible COX-2 form in the brain—converts arachidonic acid into prostaglandin H2, which is then turned into PGE2. The rise in PGE2 acts on hypothalamic receptors to raise the body’s temperature set point, producing fever. That’s why this enzyme is the key driver. The other enzymes don’t directly raise the set point: lipoxygenase makes leukotrienes, phospholipase A2 just provides arachidonic acid, and HMG-CoA reductase is involved in cholesterol synthesis.

Fever is driven by increased prostaglandin E2 production in the hypothalamus. When pyrogens stimulate the immune response, cyclooxygenase—especially the inducible COX-2 form in the brain—converts arachidonic acid into prostaglandin H2, which is then turned into PGE2. The rise in PGE2 acts on hypothalamic receptors to raise the body’s temperature set point, producing fever. That’s why this enzyme is the key driver. The other enzymes don’t directly raise the set point: lipoxygenase makes leukotrienes, phospholipase A2 just provides arachidonic acid, and HMG-CoA reductase is involved in cholesterol synthesis.