Abstract: Research of hormones and mechanisms of their action is one of the most rapidly developing branches of modern biology. During the last 15 years it has been shown that hormones regulate all vital processes: metabolism and functions as well as template syntheses and other cellular processes (proliferation etc.), determined by genome. The majority of hormones showed new effects, their action proved to be pleiotropic. The comparative analysis has shown the fundumental uniformity of biological functions and signification, the basic features and properties, molecular mechanisms of action for all types of intercellular receptor regulators' activity. Therefore they are appropriate to be combined into a complete community, so-called "hormones". The science of all hormones is to be defined as hormonology. The activity of hormones considerably changes upon many diseases. Substances, which influence hormonal systems, make 2/3 of modern medications.