Fever

- Pyrogens increase the set-point temperature.  Core temperature will be recognized as lower than the new set-point temperature by the anterior hypothalamus.  As a result, heat-generating mechanisms (e.g., shivering) will be initiated.
- Pyrogens increase the production of interleukin-1 (IL-1) in granulytic phagocytic cells.
- IL-1 acts on the anterior hypothalamus to increase  the production of prostaglandins.  Prostaglandins increase set-point temperature, setting in motion the heat-generating mechanism that increase body temperature and produce fever.
- Aspirin reduces fever by inhibiting cyclooxygenase, thereby inhibiting the production of prostaglandins.  Therefore, aspirin decreases the set-point temperature.  In response, mechanisms that cause heat loss (e.g., sweating, vasodilation) are activated.
- Steroid, like glucocorticoids inhibit the enzyme phospholipase A2; this decreases the release of arachidonic acid and the variety of substances produced from it, such as leukotrienes, prostaglandins, thromboxanes, and prostacyclin.  Cortisol owes its fever-reducing action to the hormone's ability to decrease the release of interleukin-1 from granulocytes.  However, only in massive doses will the hormone achieve the effects described.