<prompt> Pyrogens act on which site of brain ?Basal gangliaLimbic systemThalamusHypothalamus  <response>: Ans. is d i.e., Hypothalamus PyrogenesPyrogenes are substances that cause fever.Pyrogens may be exogenous or endogenousExogenous - Bacterial toxinsEndogenous - IL-1, TNF-a, IL-6, Interferons, Ciliorys neurotropic factorThese pyrogenes increase the level of PGE, in the hypothalamus that elevates the thermoregulatory set point and causes fever. 