It is a chemical information substance synthesized by highly differentiated endocrine cells and secreted directly into the blood, which affects the physiological activities of the human body by regulating the metabolic activities of various tissues and cells. The highly effective bioactive substances secreted by endocrine glands or endocrine cells, as messengers, transmit information in the body and regulate the physiological process of the body are called hormones. It is an important substance in our life.
Now, all chemicals that transmit information through blood circulation or tissue fluid are called hormones. The secretion of hormones is very small, at the level of nanogram (one billionth of a gram), but their regulatory effect is extremely obvious. Hormones have a wide range of functions, but they do not participate in specific metabolic processes, but only regulate specific metabolic and physiological processes, and adjust the speed and direction of metabolic and physiological processes, thus making the activities of the body more adaptable to changes in the internal and external environment. The mechanism of action of hormones is to transmit information to cells by binding with specific receptor proteins in cell membrane or cytoplasm, causing a series of corresponding chain changes in cells, and finally showing the physiological effects of hormones. The physiological functions of hormones include: maintaining metabolic balance and providing energy for physiological activities by regulating the metabolism of protein, sugar and fat and the metabolism of water and salt; Promote cell division and differentiation, ensure the normal growth, development and maturity of tissues and organs, and affect the aging process; Affect the development and activities of the nervous system; Promote the development and maturity of reproductive organs and regulate the reproductive process; Close cooperation with the nervous system enables the body to better adapt to environmental changes. Studying hormones can not only understand the effects and pathogenesis of some hormones on the growth, development and reproduction of animals and humans, but also diagnose diseases by measuring hormones. Many hormone preparations and their synthetic products have been widely used in clinical treatment and agricultural production. Using genetic engineering to make bacteria produce some hormones, such as growth hormone and insulin, has become a reality and is widely used in clinic.
In a broad sense, it refers to the substances that cause the body fluids to communicate with each other, but in a narrow sense, they are generally produced in fixed parts of animals (usually in endocrine glands), secreted directly into body fluids without catheters, and transported to various parts of the body to make certain changes in certain tissue activities, which are called hormones. According to their discovery of secretin, W.M.Bayliss and E.H. St-Arling (1902) first gave the name and definition of the substance "hormone" with this effect. Even a very small amount of hormones have shown their due functions, but they do not constitute metabolic substrates, but only play a role in regulating substances. Its mechanism of action is that steroid hormones bind to chromatin through the complex of hormones and intracellular receptors, which leads to the activation of transcription and the synthesis of new mRNA, and then synthesize enzyme proteins, structural proteins or regulatory proteins. The results show that this effect of hormones appears in cells. Among peptide hormones, it is considered that it reacts directly with cell membrane and plays a hormonal role through intracellular cAMP. According to chemical classification, vertebrate hormones can be divided into protein, polypeptide system (insulin, glucagon, pituitary hormone and parathyroid hormone), phenolic derivative system (adrenaline and thyroid hormone) and steroid compound system (gonadal hormone and adrenocortical hormone). The molting hormone of insect thymus hormone belongs to steroid system, while the juvenile hormone of pharynx lateral body belongs to chain hydrocarbon. In addition, the stimulating substance of the reproductive nest of starfish extracted from the radial nerve of starfish is nucleotide. No matter whether the source is cells, tissues or glands, all internal secretions with special physiological functions are called hormones (in a broad sense). Plant hormones secreted by glands, trauma hormones secreted by irregular non-glandular tissues, parachormones jointly produced by all tissues, and pheromones secreted by individuals in vitro that can play a role among individuals can all be classified into hormones and other categories. On the other hand, neuroendocrine substances formed and secreted by specific nerve cells, such as neurohypophysis hormone, can be classified as hormones in a narrow sense, while chemical transfer substances such as acetylcholine and norepinephrine are usually not classified as hormones in a narrow sense. Recently, due to the application of cybernetics, the idea of taking hormones as intercellular information transmission substances in an individual has also been strengthened.