Abstract. The endocrine system is the system that regulates the entire body as a whole. Hormones are biologically active substances of the body that are synthesized in small quantities in specialized cells of the endocrine system and are delivered through circulating fluids (for example, blood) to target cells, where they exert their regulating effect. The relationship between cells in the body is an important point in their existence and is realized with the participation of the nervous and endocrine systems. The endocrine glands produce hormones for this