Fever is an adaptive response to a variety of infectious, inflammatory, and foreign stimuli. The “febrile response” confers an immunological advantage to the host over invading microorganisms – bacterial, fungal and viral. Fever results from a cytokine-mediated reaction that results in the generation of acute phase reactants and controlled elevation of core body temperature. The anterior hypothalamus coordinates the “febrile response” in reaction to the release of endogenous pyrogenes and subsequent up-regulation of prostaglandin synthesis. An ensuing change in the hypothalamic set point for temperature regulation advances a synchronized physiologic response from CNS to periphery, on a microscopic and macroscopic level, throughout the entire human organism. This differs from hyperthermia which refers to heat retention attributable to unregulated readjustment of the thermoregulatory mechanism. Clinically, an elevation of core body temperature, whether in fever or hyperthermia, is only the most apparent manifestation of an intricate mechanism that orchestrates activation of autonomic, immunologic, neurologic, hematologic, endocrine and behavioral responses.

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