Vasopressin - an antidiuretic hormone - is produced by the hypothalamus, which is located in the posterior lobe of the pituitary gland (neurohypophysis). This hormone provides homeostasis in the human body, while maintaining water balance. So, for example, with dehydration or massive bleeding under the influence of vasopressin, mechanisms are activated to ensure the cessation of fluid loss. Thus, the antidiuretic hormone (ADH) simply does not allow us to dry.
Where is ADH synthesized?
Antidiuretic hormone is produced in the large-cell neurons of the supraoptic nucleus of the hypothalamus and binds to neurophysin (a carrier protein). Further, along the neurons of the hypothalamus, it goes to the posterior lobe of the pituitary gland and accumulates there. As needed, from there it enters the bloodstream. The secretion of ADH is affected by:
- Blood pressure (BP).
- Osmolarity of plasma.
- The volume of circulated blood in the body.
Biological effects of antidiuretic hormone
At high blood pressure, the secretion of antidiuretic hormone is suppressed and, conversely, when blood pressure drops by 40% of normal, the synthesis of vasopressin can increase by 100 times from the usual daily norm.
Plasma osmolarity is directly related to the electrolyte composition of the blood. As soon as the osmolarity of blood falls below the minimum permissible norm, increased release of vasopressin into the blood begins. With an increase in plasma osmolarity above the permissible norm, a person experiences thirst. And drinking plenty of fluids inhibits the release of this hormone. Thus, protection against dehydration is provided.
How does the antidiuretic hormone affect the change in the volume of circulating blood? With massive blood loss, special receptors located in the left atrium and called volume receptors respond to a decrease in blood volume and a drop in blood pressure. This signal enters the neurohypophysis, and the release of vasopressin increases. The hormone has an effect on the receptors of blood vessels and their lumen is narrowed. This helps to stop bleeding and prevents a further drop in blood pressure.
Disorders in the synthesis and secretion of ADH
These disorders may be associated with an insufficient amount of vasopressin or with its excess. So, for example, with diabetes insipidus, there is an insufficient level of ADH, and with excess of Parkhon syndrome.
Diabetes insipidus
With this disease, the reabsorption of water in the kidneys decreases sharply. Two circumstances can contribute to this:
- Inadequate secretion of vasopressin - then we are talking about diabetes insipidus of central origin.
- Reduced kidney reaction to ADH - this occurs with a neurogenic form of diabetes insipidus.
In patients suffering from this pathology, daily diuresis can reach 20 liters. Urine is weakly concentrated. Patients are constantly thirsty and they drink a lot of fluids. To find out exactly what form of diabetes insipidus a patient suffers from, an analog of the hormone vasopressin - the drug Desmopressin - is used. The therapeutic effect of this drug is manifested only in the central form of the disease.
Parkhon's Syndrome
It is also called the syndrome of inadequate secretion of ADH. This disease is accompanied by excessive secretion of vasopressin, while there is a reduced osmotic pressure of the blood plasma. In this case, the following symptoms appear:
- Muscle twitching and cramps.
- Nausea, lack of appetite, vomiting is possible.
- Possible lethargy, coma.
The condition of patients sharply worsens when fluid enters the body (intravenously or orally with a drink). With a sharp restriction of the drinking regimen and the abolition of intravenous infusions in patients, remission occurs.
What symptoms indicate an insufficient level of vasopressin?
If the antidiuretic hormone is not synthesized in sufficient quantities, a person may experience:
- Great thirst.
- Rapid urination.
- Dry skin, which is constantly progressing.
- Lack of appetite.
- Problems with the gastrointestinal tract (gastritis, colitis, constipation).
- Sexual problems. In men - a decrease in potency, in women - menstrual irregularities.
- Chronic fatigue.
- Increased intracranial pressure.
- Decreased vision.
What does a decrease in ADH indicate?
A decrease in blood vasopressin levels can be observed in the following situations:
- Central diabetes insipidus.
- Nephrotic syndrome.
- Psychogenic polydipsia.
What symptoms indicate increased secretion of ADH?
- Decreased daily urine output (urine output).
- Weight gain with reduced appetite.
- Lethargy and dizziness.
- Headache.
- Nausea and vomiting.
- Muscle cramps.
- Various lesions of the nervous system.
- Sleep disturbances.
Under what conditions does an increase in ADH level occur?
An increase in vasopressin can be observed in pathologies characterized by excessive secretion of this hormone, these include:
- Julien-Barre Syndrome.
- Intermittent acute porphyria.
In addition, this is possible under the following conditions:
- Brain tumors (primary or metastases).
- Infectious diseases of the brain.
- Vascular diseases of the brain.
- Tuberculous meningitis.
- Pneumonia.
Antidiuretic hormone - where to get it?
One of the most effective methods for determining ADH in the blood is radioimmunoassay (RIA). In parallel, plasma osmolarity is also determined. Analysis can be done at any endocrinology center. Many paid clinics also do such tests. Blood is donated from a vein into test tubes without any preservatives.
Before giving blood to the hormone, the antidiuretic should be a 10-12 hour break in food intake. Physical and mental stress on the eve of blood donation can distort the result of the analysis. This means that the day before the test, it is advisable not to engage in heavy physical labor, not to participate in sports, not to pass exams, etc.
Drugs that can increase ADH should be discontinued. If this is not possible for any reason, then in the direction form you need to indicate which drug was used, when and at what dose. The following drugs are capable of distorting the real level of ADH:
- estrogens;
- hypnotic;
- anesthetics;
- tranquilizers;
- Morphine
- Oxytocin;
- "Cyclophosphamide";
- "Carbamazepine";
- Vincristine;
- Chlorpropamide;
- Chlorothiazide;
- "Lithium carbonate."
An antidiuretic hormone test can be taken no earlier than a week after a radioisotope or X-ray examination.
This study allows us to differentiate nephrogenic diabetes insipidus and pituitary diabetes insipidus, as well as syndromes characterized by excessive secretion of ADH.