Hormones are substances that are synthesized in the human body using specialized endocrine glands. Each hormone has a special biological activity. At the moment, approximately 60 substances are secreted, which are secreted by the glands and have hormonal activity.
The main types of hormones
The most widespread classification of hormones depending on their chemical structure. They are divided into the following types:
- protein hormones that can be simple and complex;
- biologically active substances of peptide nature: calcitonin, oxytocin, somatostatin, glucagon, vasopressin;
- amino acid derivatives: thyroxine, adrenaline;
- biologically active substances of lipid nature: corticosteroids, female and male sex hormones;
- tissue hormones: heparin, gastrin.
As noted above, protein hormones are divided into two subspecies:
- simple: insulin, growth hormone, prolactin;
- complex: lutropin, follicle-stimulating hormone, thyroid-stimulating hormone.
Examples of hormone proteins and their functions should be considered depending on the organ in which they are synthesized. And it can be the following body structures:
- hypothalamus;
- pituitary;
- parathyroid glands;
- pancreas;
- cells of the gastrointestinal tract.
Biologically active substances of the hypothalamus
Absolutely all substances that are produced by the hypothalamus belong to the group of hormone proteins and polypeptides. Their main function is to regulate the production of hormones in the pituitary gland. Depending on how they perform this function, there are several varieties:
- releasing hormones increase the activity of the pituitary gland;
- statins inhibit the synthesis of biologically active substances by the pituitary gland;
- hormones of the posterior lobe do not affect the activity of the pituitary gland, accumulate in its posterior part before being excreted into the blood.
The hypothalamus indirectly through the pituitary gland affects the function of the thyroid gland and adrenal glands, the reproductive system, and regulates human growth.
Hypothalamic releasing hormones
The following substances belong to releasing hormones:
- growth hormone releasing hormone (SRH);
- thyrotropin releasing hormone (TRH);
- gonadotropin releasing hormone (GnRH);
- corticotropin releasing hormone (KRG).
The function of hormone proteins in this group is to increase the synthesis of the corresponding biologically active substances in the pituitary gland. Thus, SRH stimulates the production of growth hormone and prolactin, TSH enhances the production of thyroid-stimulating hormone, GnRH increases the synthesis of luteinizing and follicle-stimulating hormones, and KRH increases the production of corticotropin. Moreover, all the tropic hormones are formed in the anterior pituitary gland (there are three in total).
KRG has not only biological, but also neuronal activity. Therefore, it is still classified as a neuropeptide. Due to the transmission of KRH in nerve synapses, a person experiences feelings of anxiety, fear, anxiety, sleep and appetite disturbances, and decreased sexual activity. With prolonged exposure to corticotropin releasing hormone, persistent mental disorders develop: depression, anxiety, insomnia, and exhaustion.
TRH is also classified as a neuropeptide. He is involved in the implementation of certain mental functions. For example, its antidepressant activity has been established.
GnRH synthesis has some cyclic nature. It is produced several minutes every 1-3 hours.
Biologically active substances of the pituitary gland
Protein hormones are also substances that are synthesized in the anterior and posterior lobes of the pituitary gland. Moreover, tropic hormones are produced in the anterior region, and the formation of new substances does not occur in the posterior region, but oxytocin and vasopressin, which were previously synthesized in the hypothalamus, accumulate.
Peptide and protein structures are tropic:
- adrenocorticotropic hormone (ACTH);
- thyroid-stimulating hormone (TSH);
- luteinizing hormone (LH);
- follicle-stimulating hormone (FSH).
All of them have a stimulating effect on the peripheral endocrine glands. So, ACTH increases adrenal gland activity, TSH activates the thyroid gland, and LH and FSH activate the gonads.
Effective biologically active substances are isolated separately. They do not regulate the function of the endocrine glands, but stimulate organs that are outside the endocrine system.
Adrenocorticotropic hormone
Adrenocorticotropic hormone is directly related to the adrenal glands, namely its bark. It increases the synthesis and secretion of corticosteroids into the bloodstream. It is characteristic that only two layers of the adrenal cortex are stimulated - bundle and reticular. The glomerular zone, where mineralocorticoids are synthesized, is not influenced by tropic biologically active substances of the pituitary gland.
ACTH dimensions are small. It consists of only 39 amino acid residues. Its concentration in the blood, in comparison with other hormones, is not very high. The synthesis of this substance has a clear dependence on the time of day. This is called a circadian rhythm. Its maximum amount in the blood is observed in the morning when the body is awakened. This is due to the need to mobilize all the forces of the body after sleep. Also, the amount of these hormone proteins increases in stressful situations.
In addition to the effect of ACTH on the adrenal cortex, it also acts on structures that are not related to the endocrine system. So, it increases the breakdown of lipids in adipose tissue.
With an increase in adrenal gland activity, for example, with Itsenko-Cushing's syndrome, ACTH production decreases by the feedback mechanism. This, in turn, inhibits the synthesis of corticotropin releasing hormone in the hypothalamus.
Thyroid-stimulating hormone
Thyroid-stimulating hormone, or TSH, consists of two parts: alpha and beta. The alpha part of TSH is similar to that of gonadotropic hormones, and beta-chat is inherent only to thyrotropin. TSH regulates the growth of the thyroid gland, providing its increase in size. This substance also enhances the synthesis of thyroxine and triiodothyronine - the main thyroid hormones that are necessary for normal metabolism in the body.
Releasing hormones of the hypothalamus affect the production of TSH in the pituitary gland. A feedback mechanism also works here: with increased activity of the thyroid gland (thyrotoxicosis), the synthesis of TSH in the pituitary gland is inhibited, and vice versa.
Gonadotropin
Gonadotropic hormones (GnTH) in mammals, including humans, are represented by follicle-stimulating (FSH) and luteinizing (LH) hormones. They differ not only in their structure, but also in function. Moreover, they are slightly different depending on the gender. In women, FSH stimulates the growth and maturation of follicles; men need it to form spermatic cords and differentiate sperm.
LH in girls is involved in the formation of the corpus luteum in the ovaries, ovulation. In men, these protein hormones perform the function of testosterone secretion by the testes. Moreover, testosterone is produced not only in men, but also in women.
Answering the question, what hormones are proteins that stimulate the production of FSH and LH hormones in the pituitary gland, it is worth noting that this is only one hormone. It is called gonadotropin releasing hormone. In addition to the activity of peripheral endocrine glands, the synthesis of GnRH is regulated by the organs of the central nervous system (the limbic part of the brain).
Effector hormones of the anterior pituitary gland
Effector protein hormones perform the function of stimulating the activity of internal organs that are located outside the endocrine system. These include:
- growth hormone;
- prolactin;
- melanocyte-stimulating hormone.
Growth hormone
Growth hormone or growth hormone is a large protein that includes 191 amino acid residues. Its structure is very similar to the structure of another pituitary hormone - prolactin.
The main function of growth hormone is to stimulate bone growth and the entire body as a whole. The growth process under the influence of growth hormone is carried out by increasing the size and number of cells that are in the cartilage of the pineal gland (the extreme sections of the bones). After puberty is over, cartilage is replaced with bone. As a result, growth hormone can no longer stimulate bone growth. Therefore, a person grows to a certain age.
Excessive synthesis of growth hormone in childhood leads to the fact that the child grows too tall. But all parts of the body are enlarged proportionally. This condition is called gigantism. If somatotropin is actively produced in adults, there is a disproportionate proliferation of individual parts of the body - acromegaly.
If, on the contrary, growth hormone growth hormone was produced in insufficient quantities, dwarfism develops. The child grows very low, but the body proportions are preserved.
Biologically active substances of the pancreas
The pancreas belongs to the group of glands of mixed secretion. This means that in addition to the synthesis of hormones, it also produces enzymes that are necessary for the digestion of food in the intestines. The synthesis of protein hormones and enzymes are the two most important functions of the pancreas.
The most important biologically active substances that are produced in the pancreas are insulin and glucagon. They are antagonists of each other, that is, they perform completely opposite functions. Due to the coordinated action of these hormones, a normal carbohydrate metabolism is ensured.
Insulin is formed in islets of Langerhans from proinsulin. It reduces the concentration of glucose in the blood due to the following processes:
- increase its utilization in cells;
- inhibition of gluconeogenesis (synthesis of glucose in the liver);
- inhibition of glycolysis (breakdown of glycogen to glucose);
- stimulation of glycogenesis (the formation of glycogen from glucose).
Insulin also contributes to the formation of proteins and fats. That is, it refers to anabolic hormones. Glucagon has the exact opposite effect, and therefore it has been attributed to catabolic hormones.
Conclusion
Protein and lipid hormones are very important substances in the body. Proteins, which are synthesized mainly in the hypothalamus and pituitary gland, affect the synthesis of biologically active substances in the peripheral endocrine glands. And steroid and sex hormones, which are produced in the adrenal glands and gonads by the action of proteins, are vital for humans.
The production of biologically active substances throughout the body is coordinated, under strict control. And the violation of these functions can lead to dangerous, and sometimes irreversible consequences.