Core body temperature is maintained within a narrow range around 37 °C in normal individual. Hypothalamus acts as the body’s thermostat which regulates heat balance. Increased body temperature results from excessive heat production or interference with heat dissipation. Fever is elevation of core body temperature resulting from upward resetting of the hypothalamic thermostatic set-point caused by pyrogens. Hyperthermia is elevation of body temperature beyond the unchanged hypothalamic thermostatic set-point resulting from dysfunction of body temperature center or impairment of heat production and/or heat loss mechanisms.