Vasopressin (also known as adiuretin or antidiuretic hormone) is an oligopeptide whose molecule is composed of 9 amino acids. Vasopressin is produced by the neurons of the supraventricular and periventricular nuclei in the hypothalamus. From there, it is transported by axonal transport to the posterior pituitary gland, from which the hormone is released. Adiuretin is a substance with a short half-life, estimated to be around 20 minutes.
Vasopressin(adiuretin, ADH, AVP) is an antidiuretic hormone produced by the hypothalamus and released by the posterior pituitary gland.
The main role of vasopressin is to regulate the water balance of the human body. This hormone, however, has much more action, because it can also, among others, lead to the constriction of blood vessels and even influence human behavior. The ideal condition is one where the amount of vasopressin is adjusted to the body's needs - both excess and too little antidiuretic hormone can be the basis for the onset of the disease.
Contents:
- Vasopressin: mechanism of action and secretion regulation
- Vasopressin: deficiency causes and symptoms
- Vasopressin: causes and symptoms of excess
- Vasopressin: tests to determine its amount in the body
- Vasopressin: its analogues and antagonists and their use in the treatment of various diseases
Vasopressin: mechanism of action and secretion regulation
The release of vasopressindepends mainly on the osmolality of the blood plasma and the cerebrospinal fluid (these parameters depend on the content of electrolytes in the plasma and cerebrospinal fluid) and on the blood volume circulating. Osmolality is controlled by the so-called osmoreceptors, which are located in the hypothalamus, and information about circulating blood volume is recorded by baroreceptors (receptors that respond to changes in blood pressure), which are located in the carotid sinuses and blood vessels.
The stimulus for the release of vasopressin may be both a decrease in the volume of circulating blood (which suggests a decrease in blood pressure), but also an increase in plasma osmolality (i.e. a state in which the amounts of electrolytes in the plasma exceed physiological values). The moment it comes toAfter any of the above-mentioned phenomena, there is an increase in vasopressin secretion by the posterior pituitary gland - the body can then regain its equilibrium state via adiuretin.
Vasopressin primarily affects the kidneys and blood vessels. V2 receptors for vasopressin are present in the kidneys - they are located within the distal convoluted tubule and the collecting tubule of the nephron. Stimulation of these receptors causes increased production, as well as increased incorporation of the abovementioned elements of the glomerulus of aquaporins into the membranes. These are proteins through which water is absorbed from the urine originally formed in the kidney, which then goes back to the blood. The result of the renal action of vasopressin is that the kidneys produce more concentrated urine - the recovered water goes back into the circulating blood, which leads to an increase in blood pressure, and also to a reduction (by dilution) of blood osmolality.
The antidiuretic hormone also has its receptors within the blood vessels - these are the V1 receptors. The stimulation of these structures causes the vessels to contract. This is another mechanism by which vasopressin causes an increase in blood pressure. However, this effect is much smaller than that which occurs due to the action of a hormone on the kidney and its V2 receptors.
Other hormones can also regulate the secretion of vasopressin. This is the case with angiotensin II, which stimulates the release of vasopressin from the pituitary gland. The opposite is true in the case of atrial natriuretic peptide (ANP) - it directly inhibits the release of the aforementioned angiotensin II, and thus - indirectly - ANP reduces the release of vasopressin.
However, vasopressin influences many other processes. Aggregation of platelets is regulated by vasopressin, as adiuretin leads to the release of von Willebrand factor and the so-called factor VIII. In addition, vasopressin also influences the gluconeogenesis processes taking place in the liver. There are more and more indications that adiuretin also influences our behavior, probably because this hormone is involved in shaping human social relationships, and potentially it also has an impact on human libido.
Vasopressin: deficiency causes and symptoms
Given the role of vasopressin in the body, it is easy to see what can happen when the hormone is not properly secreted. Vasopressin deficiency leadsto excessive loss of water from the body. This may result in a very strong, constant thirst in the patient (called polydipsia), and may lead to increased urine output (called polyuria).
Physiologically, most vasopressin is secreted during night rest - otherwise, our sleep would be interrupted frequently to urinate. In patients who are deficient in vasopressin, such regulation does not exist - patients may wake up frequently at night, which may result in a constant high degree of fatigue. The symptoms listed above may appear both in the case of vasopressin deficiency and when the problem occurs. it concerns not the amount of the hormone in the body, but the defect of its effect on specific receptors. Too little vasopressin may result from disturbances in its production in the hypothalamus or its release from the pituitary gland itself - this condition is called central diabetes insipidus.
The second form of this disease, diabetes insipidus, is associated with a defect in the renal V2 receptors for vasopressin. In its course, these receptors are simply insensitive to the antidiuretic hormone, so even properly secreted vasopressin is not able to exert its physiological effect in the nephrons. attention to a certain exceptional condition. It is compulsive, i.e. compulsory, drinking water. In such a situation, a low level of vasopressin is somewhat physiological - when too much fluid is supplied to the body, vasopressin is not secreted - in order to maintain an appropriate balance, it is necessary to excrete excess fluids (and not to retain them, which would be caused by the secretion of vasopressin). You can also dehydrate yourself with too little vasopressin by consuming certain … liquids. This is the case with alcohol, as it has an inhibitory effect on the release of vasopressin.
Vasopressin: causes and symptoms of excess
Excess vasopressin, unlike its deficiency, leads to excessive water retention in the body. The condition is also serious as it can lead to hyponatremia, which is a decrease in the amount of sodium in your body. This is due to the fact that more and more water is retained, which reduces the concentration of sodium - it is supposedly "diluted" in excess fluid in the body as needed. The symptoms of excess vasopressin are mainly related to the nervous system and may include:
- headaches
- nausea and vomiting
- mood changes
- reduction of muscle tone
- convulsions
- disturbance of consciousness
A condition with too much adiuretic in the body is known as syndrome of inappropriate antidiuretic hormone hypersecretion (SIADH). SIADH may occur as a result of:
- neoplastic diseases (the syndrome may appear especially in the case of lung neoplasms, but also in connection with pancreatic, bladder, colon, central nervous system and leukemia neoplasms)
- multiple sclerosis
- epilepsy
- porphyria
- of the Guillain-Barre team
- HIV infection or AIDS development
- chronic respiratory diseases (e.g. cystic fibrosis or emphysema)
- respiratory tract infections (e.g. in the course of lung abscess or tuberculosis, but also during pneumonia)
- right ventricular failure
- taking certain medications (e.g. carbamazepine, diuretics, antidepressants, antipsychotics and morphine).
The result of these diseases is either an increased release of vasopressin from the pituitary gland, or its ectopic (i.e. outside the hypothalamus) production - some cancers may produce either vasopressin or substances similar to this hormone.
Vasopressin: tests to determine its amount in the body
Various tests are used to diagnose conditions associated with inadequate amount or incorrect activity of vasopressin in the body. One test that is used is simply to measure the amount of vasopressin in the blood. It is important, however, that in order to be able to reach any conclusions, it is important to know the parameters of plasma osmolality, therefore the above-mentioned test is carried out simultaneously with the determination of the concentration of vasopressin in the blood.
Diagnostics may also include a dehydration test and a dehydration-vasopressin test. In the first test, carried out in a hospital setting, the patient cannot drink fluids for several hours. During fluid restriction, urine osmolality and specific gravity, as well as osmolality and sodium content in blood are analyzed. In a situation where, despite the cessation of fluid supply, the patient continues to excrete uncompressed urine, diabetes insipidus may be suspected. The next stage of the diagnostic process, however, is to determine what specific type of diabetes insipidus exists in the patient - for this purpose, a supplementation of the test is performed.The dehydration-vasopressure test is based on the administration of the vasopressin analogue desmopressin to the patient. If urine specific gravity and osmolality increase after its administration, then it can be concluded that he has central diabetes insipidus associated with vasopressin deficiency. On the other hand, in the opposite situation, i.e. when, despite the administration of desmopressin, the urine parameters remain unchanged and still deviate from the norm, it suggests the existence of diabetic diabetes insipidus, i.e. the one in which vasopressin has nothing to work on, because the defect concerns the renal receptors for this hormone .
Vasopressin: its analogues and antagonists and their use in the treatment of various diseases
Considering the properties of vasopressin, it is quite easy to see that sometimes you can help patients by giving them substances with an antidiuretic hormone-like activity, and sometimes it is useful to use vasopressin antagonists. There are substances known as synthetic analogues of vasopressin, such as desmopressin and terlipressin.
Desmopressin shows diuresis-reducing properties and is therefore used in the treatment of central diabetes insipidus, but also in the treatment of bedwetting in children. Due to the fact that desmopressin (like vasopressin) can increase the release of von Willebrand factor and factor VIII from platelets, it can also be used to prevent bleeding.
Terlipressin, in turn, is a compound that acts primarily on blood vessels - this drug causes the contraction of smooth muscle cells present in these structures, thanks to which it can be used to control bleeding (e.g. from esophageal varices). In other situations, drugs that are classified as vasopressin antagonists are used. They are referred to as vaptans (tolvaptan can be mentioned as an example) and they are used, inter alia, in in the treatment of hyponatremia (low sodium concentration in the blood), cirrhosis or heart failure.