ABSTRACT
The body, if it is to achieve optimal performance, must possess mechanisms for sensing and responding appropriately to numerous biologic cues and signals in order to control and maintain its internal environment. The endocrine contribution is achieved through a highly sophisticated set of communication and control systems involving signal generation, propagation, recognition, transduction, and response. Endocrinology has a comparatively long history, but real advances in the understanding of endocrine physiology and mechanisms of regulation and control only began in the late 1960s with the introduction of sensitive and relatively specific analytical methods. Hormones are synthesized and secreted by specialized endocrine glands to act locally or at a distance, having been carried in the bloodstream or secreted into the gut lumen to act on target cells that are distributed elsewhere in the body. Hormones are chemical signals released from a hierarchy of endocrine glands and propagated through the circulation to a hierarchy of cell types.
