Pituitary: hormones and functions. Pituitary body and its functions in the body

The pituitary gland (pituitary gland or lower cerebral appendage) is the endocrine organ that is located at the base of the brain. More specifically, it is on the lower surface of it, in the bone pocket, which is called the Turkish saddle. This gland in a man of very small size, roughly the size of a pea, is a rounded formation weighing only 0.5 g. But despite such small sizes, the role of hormones produced by the pituitary gland is enormous.

Pituitary. Hormones and functions

This small gland is the main organ of our entire endocrine system. Hormones, which it produces, affect the following functions of the body:

• Reproductive;
• Exchange processes;
• growth.

Functions and hormones of the pituitary gland, which he produces, are closely related. In order to understand this question in more detail, let us first consider the structure of this endocrine gland.

Pituitary. Structure and function of the pituitary gland

It consists of three main parts: anterior, posterior and intermediate, which differ in their origin and structure. The pituitary body begins to form in the embryo on the 4th-5th week of intrauterine development. The anterior part of it is formed from the epithelial surface of the posterior wall of the oral cavity, the so-called Ratke pocket, in the form of a small oblong outgrowth. In the process of embryonic development, it grows in the direction of the intermediate brain.

The posterior lobe is formed a little later than the anterior one from the neural tissue of the midbrain, where these lobes are joined together. Even later, the intermediate portion of the pituitary gland is formed. It consists of a thin layer of cells. All three parts of the pituitary gland are in fact separate secretory glands, and each of them produces its own hormones. The pituitary body (hormones and its functions) takes a huge part in the work of the entire endocrine system of man.

Anterior pituitary gland

This fraction is called adenohypophysis and constitutes the bulk of the gland (70%). It consists of various kinds of endocrine glandular cells. Each cell type of this fraction produces its own hormone. These endocrine cells are called adenocytes. There are two types of adenocytes: chromophilic and chromophobic, both of which synthesize hormones:

• Thyrotropic hormone (TTG) - is responsible for the secretory activity of the thyroid gland.
• Adrenocorticotropic (ACTH) - stimulates the work of the adrenal cortex.
• Gonadotropic hormones, which include follicle-stimulating and luteinizing hormones (FSH, LH) responsible for reproductive function.
• Growth hormone (STH) - responsible for growth, stimulates the breakdown of fats, protein synthesis in cells and the formation of glucose.
• Luteotropic hormone, or prolactin, which regulates the instinctive care of the offspring, lactation, metabolic and growth processes.

Hormones of the pituitary gland - their physiological role in the human body is enormous.

Somatotropin

Somatotropin (or growth hormone) is not produced continuously, its release occurs only 3-4 times a day. Its secretion increases noticeably during periods of sleep, with severe physical exertion and during fasting. The development of this hormone persists throughout the life of a person, but with age is greatly reduced. Under the influence of growth hormone, the cells split fat and carbohydrates. As a result, under the influence of somatomedins produced in the liver, cell division and protein synthesis increase, thus bone growth occurs.

If the synthesis of somatotropin is for some reason insufficient, then dwarfism develops. In this case, all the proportions of the body are preserved, the physique, as a rule, is normal. Thus, the inadequacy of the function of the pituitary gland directly affects the growth of a person.

Excessive secretion of somatotropin causes gigantism. If hypersecretion occurs in childhood, then all body proportions remain, and in adulthood, increased production leads to acromegaly. This is manifested by a disproportionate lengthening of the limbs, the nose and chin, and also the tongue and all the digestive organs.

Thyroid stimulating hormone (TSH)

This hormone regulates the activity of the thyroid gland. Under its influence, secretion of triiodothyronine and thyroxine occurs. It activates the enzyme adenylate cyclase, which affects the absorption of iodine by the cells of the thyroid gland. In addition, under the influence of TSH, protein metabolism is carried out: the production of nucleic acids and protein synthesis is increased, the growth is increased and the size of thyroid cells is increased.

Synthesis of TSH is able to increase under the influence of cold. The cold reaction strengthens the production of thyroid hormones, this leads to more heat generation by the body. Glucocorticoids are able to inhibit the production of TSH, the same happens under the influence of anesthesia, pain reaction or trauma.

Excessive secretion of thyroid-stimulating hormone is manifested by clinical symptoms of thyrotoxicosis (hyperthyroidism).

Adenocorticotropic hormone

ACTH is synthesized unevenly during the day. The greatest concentration is observed in the morning from 6.00 to 8.00 hours, the minimum - in the evening from 18.00 to 23.00. ACTH regulates the synthesis of corticosteroids, which are excreted by the cells of the adrenal cortex. Secretion of corticosteroids increases with strong emotional states, such as fear, anger, chronic stress. Thus, ACTH has a direct impact on the emotional balance of a person. In the same way, the synthesis of ACTH is enhanced by severe cold and painful reactions, severe physical stress. Hypoglycemia also stimulates the production of ACTH.

Excessive secretion of this hormone can be observed with adenoma of the pituitary gland, this disease is called Itzenko-Cushing's disease. Manifestations of it are: hypertension, obesity, and fat deposits accumulate on the trunk and face, and the limbs remain normal, increased blood sugar, reduced immune defense.

Inadequate production of ACTH leads to a decrease in the synthesis of glucocorticoids, and this, in turn, is expressed by a disturbance in metabolism and a decrease in the endurance of the organism to the effect of the environment.

Gonadotropic hormones

They control the work of the gonads of both women and men. Thus, folliculotropin in women stimulates the formation of follicles in the ovaries. In the male half, this secret affects the development of the prostate and spermatogenesis (the formation of spermatozoa).

Luteoptropine regulates the formation of androgens - male hormones (testosterone, androstenedione, etc.) and estrogens - female hormones (estriol, estradiol, etc.).

Thus, the pituitary gland and its hormones take part in the work of almost all organs.

Posterior lobe of the pituitary gland

The posterior part of the pituitary gland is called the neurohypophysis, it consists of epidermal cells called pituitary cells. Neurohypophysis, as well as adenohypophysis, produces hormones. Hormones of the posterior lobe of the pituitary:

• Oxytocin;
• Vasopressin;
• Asparotocine;
• Vasotocin;
• Glumithocin;
• Valitocin;
• Isotocin;
• Mesotocin.

All these hormones perform their specific functions in the human body. Let's talk about some of them separately.

Oxytocin

So, the hormone oxytocin affects the contraction of the uterine muscles during childbirth. On the surface of cell membranes are special receptors, sensitive to oxytocin. During the course of pregnancy, this hormone does not rise to a level that can cause contractile activity of the uterus. Only immediately before the birth itself, under the influence of female estrogen hormones, sensitivity to oxytocin increases and birth occurs. This also leads to a reduction in myoepithelial cells located in the mammary glands, which stimulates the production of milk.

The effect of oxytocin on the male body has not been adequately studied. It is believed that he is able to influence the work of the walls of the intestine, bile and bladder.

Vasopressin (ADH)

Vasopressin (it is also called antidiuretic hormone - ADH) performs two functions in the body. It has an antidiuretic effect, i.e. Enhances the reabsorption of water in the collecting tubes of the kidneys and, in addition, it affects the smooth muscles of the arterioles (small blood vessels that drain from the arteries), i.e. Is able to narrow their lumen. In physiological concentration, this action does not cause significant effect on the body, and in pharmacological doses with artificial introduction of ADH in pure form, the arterioles narrow significantly, which causes an increase in pressure.

Thus, the hormones of the posterior lobe of the pituitary gland, when insufficiently developed, can induce diabetes insipidus (antidiuretic effect) at which up to 15 liters of fluid per day can be lost (excreted together with urine). This loss must be constantly replenished. People with diabetes insipidus are constantly thirsty.

Intermediate lobe of the pituitary gland

Intermediate share also produces a number of hormones, for example, they include melanostimulating hormone, which is responsible for the color of the skin and hair. Under its influence, pigment melanin is formed, which plays a significant role in the race of people.

Significance of pituitary hormones

The pituitary body (hormones and functions described above) works together with the hypothalamus (the department of the intermediate brain), more precisely, its neurosecretory nuclei. Together they form a hypothalamic-pituitary system. It controls the work of all peripheral endocrine glands. Violation of the pituitary (hormonal disorders) leads to serious consequences. Such problems are dealt with by doctors endocrinologists.

The pituitary gland and its functions in the body are very important. The correct work of all organs and systems depends on them.

Diseases and pathologies

When problems arise in such a small endocrine gland as the pituitary gland, hormones and functions of it work incorrectly, and in the human body serious pathologies can develop:

• acromegaly;
• gigantism;
• Diabetes insipidus;
• Hypophyseal hypothyroidism or hyperthyroidism;
• Hypophyseal hypogonadism;
• Hyperprolactinemia;
• Pituitary fascism;
• Itenko-Cushing's disease;
• Shihan syndrome.

Such diseases can be observed if the pituitary does not synthesize one hormone or several, or, conversely, too much blood enters them. Functions and hormones of the pituitary gland for the body are important. Their violations can cause a number of pathologies that require a serious approach and often require hormonal therapy.