Mechanism of action of steroid hormones – the theory of gene expression. Steroid hormones have a small molecular mass and are fat-soluble, and can be transported into target cells through diffusion or carrier, and after entering the cells, the hormone first binds to the receptor in the cytoplasm to form a hormone-receptor complex, which undergoes allosteric access to the ability to penetrate the nuclear membrane under the participation of suitable temperature and Ca2+.
After the hormone enters the nucleus, it binds to the receptors in the nucleus to form complexes. This complex binds to a non-histone specific site in chromatin and initiates or inhibits DNA transcription at that site, thereby promoting or inhibiting the formation of mRNA, resulting in inducing or decreasing the synthesis of certain proteins (mainly enzymes) to achieve their biological effects. A hormone molecule can generate thousands of protein molecules, thus realizing the amplification function of hormones.
Hormone response during muscle activityWhen muscle activity occurs, the level of various hormones, especially those that mobilize energy supply, changes to varying degrees, and affects the metabolic level of the body and the functional level of various organs. The amount of certain hormones during exercise and during recovery after exercise is measured and compared with the resting value, and the change is called the hormonal response to exercise.
Fast-reactive hormones, such as epinephrine, norepinephrine, cortisol, and adrenocorticotropic hormone, are markedly elevated in the plasma immediately after exercise begins and peak for a short period of time.
After the exercise of intermediate-reactive hormones begins, the plasma slowly and steadily rises and peaks within a few minutes, such as aldosterone, thyroxine, and vasopressin.
Slow-response hormones do not change immediately after the start of exercise, and only slowly increase when exercise reaches 30~40min, and reach a peak at a later time, such as growth hormone, glucagon, calcitonin and insulin.