The pituitary gland (pituitary gland or lower cerebral appendage) is an endocrine organ located at the base of the brain. More specifically, on the lower surface of it, in the bone pocket, which is called the Turkish saddle. This gland in humans is very small in size with about a pea, is a rounded formation weighing only 0.5 grams. But despite such a small size, the role of hormones produced by the pituitary gland is huge.
Pituitary. Hormones and functions
This small gland is the main organ of our entire endocrine system. The hormones that it produces affect the following body functions:
- reproductive;
- metabolic processes;
- height.
The functions and hormones of the pituitary gland that it produces are closely related. In order to understand this issue in more detail, let us first consider the structure of this endocrine gland.
Pituitary. The structure and functions of the pituitary gland
It consists of three main shares: front, back and intermediate, which differ in their origin and structure. The pituitary gland begins to form in the embryo at 4-5 weeks of fetal development. Its front lobe 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 diencephalon.
The posterior lobe is formed a little later than the anterior of the nerve tissue of the diencephalon, where these lobes connect. Even later, an intermediate pituitary gland is formed. It consists of a thin layer of cells. All three lobes of the pituitary gland are essentially separate secretory glands, and each of them produces its own hormones. The pituitary gland (hormones and its functions) takes a huge part in the work of the entire endocrine system of a person.
Anterior Pituitary Gland
This share is called the adenohypophysis and makes up the bulk of the gland (70%). It consists of various kinds of endocrine glandular cells. Each type of cell in this lobe produces its own hormone. These endocrine cells are called adenocytes. There are two types of adenocytes: chromophilic and chromophobic, both synthesize hormones:
- Thyroid-stimulating hormone (TSH) - is responsible for the secretory activity of the thyroid gland.
- Adrenocorticotropic (ACTH) - stimulates the adrenal cortex.
- Gonadotropic hormones, which include follicle-stimulating and luteinizing hormones (FSH, LH), are responsible for reproductive function.
- Growth hormone (STH) - is 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 offspring, lactation, metabolic and growth processes.
Pituitary hormones - their physiological role in the human body is huge.
Growth hormone
Growth hormone (or growth hormone) is not produced continuously, its release occurs only 3-4 times a day. Its secretion increases markedly during periods of sleep, during heavy physical exertion and during fasting. The production of this hormone persists throughout a person’s life, but decreases significantly with age. Under the influence of growth hormone in the cells, fat and carbohydrate are broken down. As a result, under the influence of somatomedins produced in the liver, cell division and protein synthesis are enhanced, thus, bone growth occurs.
If the synthesis of growth hormone for some reason is insufficient, then dwarfism develops. In this case, all body proportions are preserved, physique, as a rule, is normal. So, insufficiency of the pituitary gland function directly affects human growth.
Excessive secretion of growth hormone causes gigantism. If hypersecretion occurs in childhood, then all body proportions are preserved, and in adulthood, increased production of it leads to acromegaly. This is manifested by a disproportionate lengthening of the limbs, the nose and chin are enlarged, as well as the tongue and all digestive organs.
Thyroid-stimulating hormone (TSH)
This hormone regulates the activity of the thyroid gland. Under its influence, the 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 increase, growth and the size of thyroid cells increase.
The synthesis of TSH is able to increase under the influence of cold. A cold reaction enhances the production of thyroid hormones, this leads to a greater formation of heat by the body. Glucocorticoids are able to inhibit the production of TSH, the same thing 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 throughout the day. The highest 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 secreted by the cells of the adrenal cortex. Corticosteroid secretion increases with strong emotional states such as fear, anger, and chronic stress. Thus, ACTH has a direct effect on the emotional balance of a person. In the same way, the synthesis of ACTH is enhanced by severe cold and pain reactions, severe physical stress. Hypoglycemia also stimulates the production of ACTH.
Excessive secretion of this hormone can occur with pituitary adenoma, this disease is called Itsenko-Cushing's disease. Its manifestations are: hypertension, obesity, and fat deposits accumulate on the body and face, and the limbs remain normal, an increase in blood sugar concentration, a decrease in immune defense.
Insufficient production of ACTH leads to a decrease in the synthesis of glucocorticoids, and this, in turn, is expressed by a violation of metabolism and a decrease in the body's endurance to environmental influences.
Gonadotropins
They control the work of the gonads of both women and men. So, 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 (sperm formation).
Luteoptropin regulates the formation of androgens - male hormones (testosterone, androstenedione, etc.) and estrogen - female hormones (estriol, estradiol, etc.).
Thus, the pituitary gland and its hormones take part in the work of almost all organs.
Posterior Pituitary Gland
The posterior lobe of the pituitary gland is called the neurohypophysis, it consists of epidermal cells called pituiti. The neurohypophysis, just like the adenohypophysis, produces hormones. Hormones of the posterior pituitary gland:
- oxytocin;
- vasopressin;
- asparotocin;
- vasotocin;
- glumitocin;
- 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 muscles of the uterus during childbirth. On the surface of cell membranes are special receptors that are sensitive to oxytocin. During pregnancy, this hormone does not increase to a level that can cause contractile activity of the uterus. Only immediately before childbirth itself under the influence of female hormones estrogens does sensitivity to oxytocin increase and childbirth occurs. It also leads to a reduction in myoepithelial cells located in the mammary glands, which stimulates milk production.
The effect of oxytocin on the male body is not well understood. It is believed that it is able to affect the functioning of the walls of the intestine, gall and bladder.
Vasopressin (ADH)
Vasopressin (also called antidiuretic hormone - ADH) has two functions in the body. It has an antidiuretic effect, i.e. enhances the reabsorption of water in the collecting ducts of the kidneys and, in addition, it affects the smooth muscles of arterioles (small blood vessels extending from the arteries), i.e. able to narrow their clearance. In physiological concentration, this action does not cause a significant effect on the body, and in pharmacological doses, with the artificial administration of ADH in pure form, arterioles significantly narrow, which causes an increase in pressure.
Thus, hormones in the posterior pituitary gland, when they are insufficiently produced, can cause diabetes insipidus (antidiuretic action) in which up to 15 liters of fluid can be lost per day (excreted with urine). This loss must be constantly replenished. People with diabetes insipidus are constantly thirsty.
Intermediate pituitary gland
The intermediate fraction 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, the pigment melanin is formed, which plays a significant role in the racial affiliation of people.
The Importance of Pituitary Hormones
The pituitary gland (hormones and its functions described above) works together with the hypothalamus (the part of the diencephalon), more precisely, its neurosecretory nuclei. Together they form the hypothalamic-pituitary system. It controls the work of all peripheral endocrine glands. Impaired pituitary function (hormonal imbalance) leads to serious consequences. Doctors endocrinologists deal with such problems.
The pituitary gland and its functions in the body are very important. The correct operation of all organs and systems depends on them.
Diseases and pathologies
If problems arise in such a small endocrine gland as the pituitary gland, hormones and its functions do not work correctly, and serious pathologies can develop in the human body:
- acromegaly;
- gigantism;
- diabetes insipidus;
- pituitary hypothyroidism or hyperthyroidism;
- pituitary hypogonadism;
- hyperprolactinemia;
- pituitary dwarfism;
- Itsenko-Cushing's disease;
- sheehan syndrome.
Such diseases can be observed if the pituitary gland does not synthesize one or several hormones, or, conversely, too many of them enter the bloodstream. The functions and hormones of the pituitary gland for the body are important. Their disorders can cause a number of pathologies that require a serious approach and often require hormone therapy.