The action, effects and functions of a hormone

Despite the diversity of hormones - endocrine, paracrine, autocrine or pheromones - they all influence intracellular events by intracellular signalling mechanisms, and the number of such mechanisms is remarkably small, hi this chapter, the signalling mechanisms, the effects and the functions of hormones are described, discussed and illustrated by reference to selected hormones. In addition, the principles underlying the mechanisms by which hormones affect the biochemistry in cells are discussed. 

It is first necessary to clarify terminology in this field. The terms action, effect and Junction of a hormone are often used indiscriminately. Since there are no clear-cut definitions, this can be confusing. Consequently, definitions, even if only operational, are put forward here and are used throughout this chapter. 

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