Glucocorticoid hormones (GC) do not have a special target organ but directly or indirectly control nearly all metabolic and physiological processes and are mainly responsible for maintaining homeostasis and the organisms response under various conditions.GC preparations are used in medicine in various diseases for more than 60 years.Nevertheless, there is no specific parameter characterizing the effect of GC on the organism which would be similar to blood glucose for insulin and allow researchers or clinicians to assess the tissue provision with GC and the real need in them, compare efficiencies of GC preparations, and predict the organisms response in some cases (e.g.surgery, physical exercise ("the stress price")), as well as effect of GC therapy in endocrine and non-endocrine diseases.Blood tyrosine seems promising as such a parameter because it is mainly determined by the GC-dependent liver enzyme tyrosine aminotransferase.Clinical observations and experimental data will be presented and discussed.