Hormones are transliterated as hormones. The original meaning of Greek is "ascending activity", which plays an important role in regulating the metabolism, growth, development and reproduction of the body.

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. W.M.Bayliss and E. H. St.-Arling (1902) first gave the name and definition of the substance "hormone" with this effect according to their discovery of substance secretin. 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.

[Edit this paragraph] Make

Hormones are made by endocrine cells.

There are two kinds of endocrine cells in human body: gregarious and dispersed.

Form endocrine glands in society, such as pituitary gland in skull, thyroid gland and parathyroid gland in front of neck, adrenal gland, islet, ovary and testis in scrotum in stomach.

Scattered, such as gastrointestinal hormone cells in gastrointestinal mucosa and peptide hormone secretion cells in hypothalamus.

Every endocrine cell is a small workshop for producing hormones.

The concentration of hormones produced by a large number of endocrine cells has become a force to be reckoned with.

Hormones are chemicals. At present, the chemical structures of various hormones are basically clear. According to the chemical structure, it can be roughly divided into four categories. The first category is steroids, such as adrenocortical hormone and sex hormone. The second category is amino acid derivatives, including thyroxine, adrenomedullin and pineal hormone. The structure of the third kind of hormones is peptide and protein, such as hypothalamic hormone, pituitary hormone, gastrointestinal hormone and calcitonin. The fourth category is fatty acid derivatives, such as prostaglandin. Action hormone is an important substance to regulate the normal activities of the body. None of them can start a new metabolic process in the body. They do not directly participate in the transformation of matter or energy, but directly or indirectly promote or slow down the original metabolic process in the body. If growth and development is the original metabolic process of human body, the increase of growth hormone or other related hormones can accelerate this process, while the decrease will delay growth and development. Hormones play an important role in regulating human reproduction, growth, development, various other physiological functions, behavioral changes and adaptation to the internal and external environment. Once the hormone secretion is unbalanced, it will bring diseases. Hormones only play a unique role in certain tissues or cells (called target tissues or target cells). Every tissue and cell in the human body can be the target tissue or cell of one hormone or another hormone. For each hormone, one or more tissues and cells can be selected as the target tissues or cells of the hormone. For example, growth hormone can play a unique role in bones, muscles, connective tissues and internal organs, making the human body grow tall and strong. But muscle is also the target tissue of androgen and thyroxine. Although the physiological functions of hormones are very complicated, they can be summarized into five aspects: First, they provide energy for life activities and maintain the dynamic balance of metabolism by regulating the metabolism of protein, sugar and fat, water and salt. Second, promote cell proliferation and differentiation, affect cell aging, ensure the normal growth and development of tissues and organs, as well as cell renewal and aging. For example, growth hormone, thyroid hormone and sex hormone are all hormones that promote growth and development. Third, promote the development and maturity of reproductive organs, reproductive function, and secretion and regulation of sex hormones, including a series of reproductive processes such as oviposition, ovulation, spermatogenesis, fertilization, implantation, pregnancy and lactation. Fourth, it affects the development and activities of the central nervous system and autonomic nervous system, as well as its relationship with learning, memory and behavior. Fifth, closely cooperate with the nervous system to adjust the body's adaptation to the environment. It is difficult to completely separate the functions of the above five aspects, and no matter which one, hormones only play the role of messengers, transmit some information about physiological processes, accelerate or slow down physiological processes, and cannot cause any new physiological activities.

[Edit this paragraph] Its functional characteristics

1. High specificity includes tissue specificity and effect specificity. The former means that hormones act on specific target cells, target tissues and target organs. The latter means that hormones selectively regulate specific links in the process of gratitude for a generation. For example, glucagon, adrenaline and glucocorticoids all have the function of raising blood sugar, but glucagon mainly acts on liver cells, and directly transports glucose into the blood by promoting the decomposition of hepatic glycogen and strengthening gluconeogenesis; Adrenaline mainly acts on skeletal muscle cells, promotes muscle glycogen decomposition and indirectly supplements blood sugar; Glucocorticoid supplements blood sugar mainly by stimulating skeletal muscle cells, decomposing protein and amino acids, and promoting gluconeogenesis of liver cells. The role of hormones begins with the combination of hormones and receptors. Specific sex hormone binding proteins mediated by target cells are called hormone receptors. Receptors are generally glycoproteins, some of which are distributed on the surface of target plasma membrane, called cell surface receptors; Some are distributed inside cells, called intracellular receptors, such as thyroxine receptors.

2. Very efficient hormones have high affinity with receptors, so hormones can combine with receptors at very low concentrations to produce regulatory effects. The concentration of hormones in the blood is very low. Generally, the concentration of protein hormone is10-10-12 mol/L, and other hormones are10-6-10-9 mol/L. Moreover, hormones play a role by adjusting the amount and activity of enzymes, which can amplify the regulatory signal. The intensity of hormone action is related to the number of complex between hormone and receptor, so maintaining appropriate hormone level and receptor number is a necessary condition to maintain the normal function of the body. For example, insufficient insulin secretion or insulin receptor deficiency can lead to diabetes.

3. The multi-level regulation of endocrine regulation is multi-level. Hypothalamus is the highest center of endocrine system. It controls the hormone secretion of the pituitary gland by secreting neurohormones, that is, various release factors (RF) or release inhibitory factors (RIF), and the pituitary gland controls the hormone secretion of the thyroid gland, adrenal cortex, gonads and islets by releasing gonadotropins. There is a relationship between control and controlled between related levels, but the controlled can also react to the controller through feedback mechanism. For example, the hypothalamus secretes thyrotropin-releasing factor (TRF), which stimulates the anterior pituitary gland to secrete thyrotropin (TSH), so that the thyroid gland secretes thyroxine. When the concentration of thyroxine in blood rises to a certain level, thyroxine can also feedback and inhibit the secretion of TRF and TSH. The role of hormones is not isolated. Endocrine system not only has the control and feedback relationship between superior and subordinate, but also many hormones play a regulatory role at the same level. The interaction between hormones has both synergistic and antagonistic effects. For example, blood sugar regulation, glucagon and so on raise blood sugar, and insulin lowers blood sugar. They interact to stabilize blood sugar at a normal level. The two hormones that positively and negatively regulate a physiological process maintain a certain balance, and once broken, it will lead to endocrine diseases. The synthesis and secretion of hormones are regulated by the nervous system.

[Edit this paragraph] Research

1853, Barnard of France studied the gastric juice of various animals and found that the liver has many incredible functions. Bernard thinks it contains a substance to accomplish this function. But he didn't develop this substance. It's actually a hormone.

1880, ostwald, a German, proposed a large number of substances containing iodine from the thyroid gland, and confirmed that it was a substance for regulating thyroid function. Later, I learned that this is also a hormone.

1889, Barnard's student West Quarder discovered the function of another hormone. He thinks that the testicles of animals must contain substances that can activate body functions, but they have never been found.

190 1 year, Takamine jūkichi, a Japanese researcher in the United States, extracted a substance that regulates blood pressure from the accessory kidney of cattle and made it into crystals, named adrenaline, which is the first hormone crystal extracted in the world.

1902, British physiologists starling and Bayless found that when food enters the small intestine, due to the friction of food on the intestinal wall, the intestinal mucosa will secrete a very small amount of substances into the blood and send them to the pancreas, which will secrete pancreatic juice immediately after receiving it. They extracted this substance and injected it into the blood of mammals. They found that animals secrete pancreatic juice immediately even if they don't eat, so they named this substance "pancreatic juice".

Later, starling and Bayless named the substance mentioned above as "hormone", which is small in quantity but has physiological function and can cause the reaction of living organs.

Since the word hormone appeared, new hormones have been discovered continuously, and people's understanding of hormones is still deepening and expanding.

[Edit this paragraph] How hormones are released.

Mainly includes:

① Long-distance secretion, after hormone release, it directly enters capillaries and is transported to distant target organs through blood circulation;

(2) paracrine, that is, hormone enters extracellular fluid after release and reaches adjacent target cells through diffusion;

③ Nerve secretion, that is, hormones synthesized by nerve cells flow along the axon and are transported to the connected tissues, or are released from nerve endings to capillaries and transported to target cells through blood;

(4) Autosecretion, after the hormone is secreted into extracellular fluid, it acts on the secretory cell itself.

[Edit this paragraph] Hormone metabolism

There are many similarities in the synthesis, storage, release, transportation and metabolism of hormones in the body, but most of these contents belong to the biochemical category. This chapter only briefly describes the aspects closely related to physiology as follows.

(1) synthesis and storage

Hormones with different structures have different synthetic pathways. Peptide hormones are generally synthesized on ribosomes in secretory cells through translation process, which is basically similar to the synthesis process of protein. After synthesis, they are stored in small particles of Golgi apparatus and released under suitable conditions. Amine hormones and steroid hormones are mainly synthesized in secretory cells through a series of unique enzymatic reactions. The former substrate is amino acid and the latter substrate is cholesterol. If the function of endocrine cells themselves declines or lacks a certain enzyme, it will reduce hormone synthesis, which is called a certain endocrine gland dysfunction; Hyperfunction of endocrine cells and increased synthesis and secretion of hormones is called hyperfunction of endocrine glands. Both belong to non-physiological state.

The amount of hormones stored in various endocrine glands or cells can be different. Except for the thyroid gland, the amount of hormones stored in other endocrine glands is relatively small, and they are released into the blood (secretion) after synthesis, so under appropriate stimulation, it is generally necessary to accelerate synthesis.

(2) Hormone secretion and its regulation

The secretion of hormones has a certain law, which is not only regulated by the body, but also influenced by external environmental information. Hormone secretion has an important influence on body function.

1. Periodicity and Stages of Hormone Secretion Due to the periodic changes of geophysical environment and the long-term adaptation of the body to the social living environment, the secretion of hormones has obvious time rhythm, and the concentration of hormones in blood fluctuates with the cycle of day, month or year. This periodic fluctuation has nothing to do with the fluctuation caused by other stimuli, and may be controlled by the "biological clock" of the central nervous system.

2. The types and concentrations of hormones in the blood. After the hormone is secreted into the blood, one part moves with the blood in a free form, and the other part combines with protein, which is a reversible process. That is, the free type+binding protein binding type, but only the free type has biological activity. Different hormones bind to different protein, and the binding ratio is different. The process of metabolism and excretion of combined hormone in liver is longer than that of free hormone, which can prolong the action time of hormone. Therefore, the combined type can be regarded as a temporary reservoir of hormones in the blood. The concentration of hormones in blood is also an index of endocrine gland function, which remains relatively stable. If the concentration of hormone in the blood is too high, it often indicates that the endocrine glands or tissues secreting this hormone are hyperactive; Too low means that the function is low or insufficient.

3. As mentioned above, the regulation of hormone secretion is an important factor to maintain the normal function of the body, so whether the corresponding endocrine glands can secrete or stop secreting in time after receiving the information. This requires the regulation of the body, so that the secretion of hormones can ensure the needs of the body; Without causing too much harm to the body. The stimulation that causes the secretion of various hormones can be varied, involving many aspects, similar aspects and different aspects, but there are many similarities and differences in the regulatory mechanism, which are briefly described as follows.

When a message causes a hormone to start secreting, the information that often adjusts or stops its secretion is also fed back. That is, endocrine cells secreting hormones receive the information of hormone concentration in target cells and blood at any time, or reduce their secretion (negative feedback) or increase their secretion (positive feedback), and the negative feedback effect is often common. The simplest feedback loop exists between endocrine glands and body fluid components. For example, an increase in blood glucose concentration can promote insulin secretion and reduce blood glucose concentration. After the blood sugar concentration drops, the effect on insulin secretion of islet is weakened, and insulin secretion is reduced, thus ensuring the relative stability of blood sugar concentration. Another example is that the regulatory peptide secreted by hypothalamus can promote the secretion of gonadotropin by adenohypophysis, and then promote the secretion of hormone by the corresponding target gland for the body's needs. When this hormone reaches a certain concentration in the blood, it can feedback inhibit the secretion of adenohypophysis or hypothalamus, thus forming a functional axis of hypothalamus-adenohypophysis-target gland and forming a closed loop. This regulation is called closed-loop regulation, which can be divided into long feedback, short feedback and ultra-short feedback according to the length of the regulation distance. It should be pointed out that in some cases, hormones secreted by endocrine cells in the late stage can also promote the secretion of glands in the early stage, which has a positive feedback effect, but it is rare.

On the basis of closed loop, the central nervous system can receive various stimuli from the external environment, such as stress, light and temperature, and then connect the endocrine system with the external environment through the hypothalamus to form an open loop, which promotes the secretion of endocrine glands at all levels and makes the body better adapt to the external environment. At this point, the closed loop temporarily fails. This regulation is called open-loop regulation.

(3) Hormone metabolism

It takes different lengths of time for hormones to be secreted into the blood, metabolized and disappeared (or their biological activities disappeared). In order to express the speed of hormone renewal, the so-called half-life of hormone activity in blood is generally used as a measure. Some hormones have a half-life of only a few seconds; Others can last for a few days. Half-life must be distinguished from the speed and duration of action. The speed of hormone action depends on its mode of action; The duration of the action depends on whether the secretion of hormones continues. The disappearance of hormones can be diluted by blood, absorbed by tissues, inactivated by metabolism, and excreted in urine and feces through liver and kidney.