The tutorial contains material on the structure and biological role of hormones, enzymes and prostaglandins in the life of animals. The relationship of hormones with various factors of influence on the body in postnatal ontogenesis (season, blood content, etc.) on the hormonal profile and the manifestation of economic signs is briefly described. Attention is paid to the practical value of biologically active substances, the possibility of using indicators of the hormonal profile of blood serum as a test for predicting productivity at a young age, for example, fertility of fur animals, dairy productivity of cattle.