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Prolactin is a peptide hormone which is produced a front share of a hypophysis. This hormone belongs to group of prolaktinpodobny proteins in which also Somatotropinum, placental lactogen and proliferin.
The physiological role of this hormone so finally is also not found out, however all known effects of prolactin anyway have communication with reproduction. Body a target of this hormone are mammary glands as it is extremely necessary for a lactation, colostrum secretion increase, for its transformation into adult milk, colostrum maturing. Besides prolactin is responsible for stimulation of development and growth of mammary glands, increases in quantity a channel and segments of mammary glands. Receptors of this hormone and in many other systems and bodies (immune system, the central nervous system, a placenta) were found, however from action on such bodies remains to unknown so far.
Development by a hypophysis of prolactin is on regulation of a hypothalamus. Regulation is connected with the principle of oppression of a special factor which in is a hypothalamus. One of such factors is amine dopamine. At the termination of its development there is an increase in blood of concentration of prolactin. Recently the opinion was expressed that decrease in production of dopamine is not the only mechanism of increase in level of prolactin in an organism. Increase of level of hormone of estrogen stimulates production of prolactin due to stimulation of growth of cells which emit prolactin, and also cosecrete it. Some peptides of the person also regulate production of prolactin.
When the child is put to a breast, he sucks a nipple therefore there is an irritation of receptors which are on a nipple. These receptors send a signal to a brain, namely – to a hypothalamus. Having received a signal, the hypothalamus begins allocation of prolactins-releasing-factors. They, in turn, also stimulate production of the prolactin. But despite the high content of prolactin and during pregnancy, the lactation does not begin. It is connected with the fact that hormone progesterone slows down release of milk. At the placenta birth concentration of progesterone sharply falls, and the lactation then becomes possible.
Some cells of a hypophysis which emit prolactin in addition to it are capable to emit also somatotropic hormone. According to scientists, it is connected with the general progenitors.
Stressful states, psychoses, severe pains, depressions, alarms are capable to increase production of this hormone considerably. The greatest secretion of prolactin is noted during pregnancy and the period of a lactation, that is release of milk. During pregnancy increase in level of prolactin increases because of the increased concentration of estrogen. The increased concentration of prolactin results maturing of mammary glands, and also their increase and preparation for a lactation. Also the level of this hormone increases at acceptance of high doses of alcohol, drugs, some antidepressants, normotimik, tranquilizers, psychotropic drugs, especially anti-psychotics, and also at reception of contraceptive tablets, estrogen, some drugs against vomiting. Decrease in secretion of prolactin happens at reception of antagonists, glucocorticoids and hormones of a thyroid gland.
The main objective of prolactin consists in maintenance formation of milk at women. After the delivery the level of the last sharply falls, and then the level of prolactin is supported by nipple receptors. Suction by the child of a breast also leads to activation of hormone of oxytocin which is produced in back hypophysis shares. It provides removal of breast milk. Thus, prolactin is responsible for formation of milk, filling of a breast with it prior to the following feeding, but it is not connected with its allocation. Sometimes it happens that at newborns allocation from nipples of milk substance which quite often call "milk of witches" is observed. The prolactin circulating in mother's milk till the birth of the child had some influence on the child, as led to his allocation. Usually release of such milk at newborns is observed in the first days after the birth then izchezat.
Also prolactin influences braking of a cycle of an ovulation and approach of new pregnancy, promotes extension of life of a yellow body of ovaries, reduces production of estrogen ovaries and progesterone a yellow body. Such physiological mechanism normal prevents approach of pregnancy during breastfeeding, and also in certain cases approach of periods.
Also some researches show that prolactin possesses some anesthetizing influence. Decrease in production of prolactin by means of special substances leads to strengthening of feeling of pain when carrying out animal experiments. Allegedly, one their mechanisms of effect of anesthetics of opiate analgetics, and so anesthetizing effect of some antidepressants, tranquilizers, anti-psychotics the prolactin secretion increase caused by them is. Perhaps, this effect of prolactin is connected the kusaniye the child of a nipple did not lead to excessive pain at mother. One more important ability of prolactin consists in providing an orgasm, it brakes effect of the domafin who is responsible for sexual excitement. Thus, the level of prolactin can demonstrate sexual relaxation and satisfaction.
Besides, there is an opinion that this hormone participates in processes of immune system. Increase in its secretion by leukocytes and lymphocytes happens at inflammatory processes, immunity activation, infections, and decrease – at immunosuppression (antineoplastic himiopreparata, glucocorticoids, immunodepressants). The surface of a set of cells which take part in immune processes has the special receptors sensitive to prolactin.
Also prolactin reduces concentration of sex hormones – testosterone at men and estrogen at women.
Level of prolactin fluctuates within a day, normal its maximum is observed in a stage of "REM sleep", and also early in the morning. Increase of level of hormone can be caused by sexual intercourse, meal, an exercise stress. The increased level can testify about:
- Amenorrhea syndrome
- Galactorrhoea syndrome
- To Giperterioza
- Hypothalamus diseases
- To adenoma, hypophysis dysfunction
- Disturbance of work of ovaries
- Renal failure
- Autoimmune diseases
- B6 hypovitaminosis
- Injury of a thorax
Reception of estrogen, antihistaminic drugs, some other drugs.
Giperprolaktinemiya is patholologically the increased prolactin level in an organism. Such state can be pathological and physiological. The second look is not connected with any disturbances or diseases, increase happens during a dream, feeding by a breast, etc. The pathological giperprolaktinemiya can functional and organic. Functional develops as a result of various diseases, such as a syndrome of sclerocystic ovaries, a chronic renal failure, cirrhosis, gipoterioz.
This state can be followed by disturbance of a menstrual cycle. The increased level can lead to a breast cancer, adenoma of mammary glands, a makromastiya, increase in mammary glands, increase of level of a sexual inclination, emergence of frigidity, an anorgazmiya, development of infertility. Strong increase of concentration can bring to a galactorrhoea.
Lowering of the level of prolactin can be an indicator:
- Reception of some medicines (anticonvulsant drugs: valproic acid, carbamazepine; dofaminergichesky means; morphine; secretin);
- Postmature pregnancy when concentration of estrogen, so and concentration of prolactin falls;
- Hypophysis apoplexies (Shikhan's syndrome) – functional insufficiency of an adenohypophysis. The apoplexy develops at strong blood losses at childbirth.