ABSTRACT
Hormonal communication is an essential physiological process for the development, survival and reproduction of individuals. Hormones are messenger molecules responsible in part for gender characteristics, the regulation of vital biological constants (glycemia, calcemia, blood protein level, plasma and cellular pH, etc.), and important behavioral components (sexual behavior, reaction to stress, psychological states, etc.). Produced by hormone-synthesizing cells, they reach target cells according to three different modes. Distant cellular communication via general bloodstream is designated as endocrine. Paracrine refers to transfer to neighboring cells. Autocrine means that cells can produce molecules acting within themselves. We do not deal here with pheromones, which establish communication between separate organisms (for instance, some pregnene steroids are secreted into water by female fishes and influence male behavior).
