The endogenous hormone adiuretin or antidiuretic hormone is produced by nerve cells in the hypothalamus, a part of the human [[diencephalon]]. Its main purpose is to control water balance in the body. An imbalance in quantity and production can cause a number of medical conditions.
What is antidiuretic hormone?
Schematic diagram showing the anatomy and structure of the endocrine (hormone) system. Click to enlarge. Adiuretin is also known as ADH (antidiuretic hormone), vasopressin, and AVP (arginine vasopressin). The most common name is ADH, which is made up of the words “anti” for “against” and “diuresis” (= excretion of urine by the kidneys). Since the hormone promotes the recovery of water from the kidneys, it acts in the opposite direction to urine excretion, which explains the name. ADH, along with oxytocin, is considered the effect hormone of the hypothalamus. This group of hormones acts directly on the cells of the target organs without taking a detour via body glands. The basic structure of ADH consists of the amino acids phenylalanine, cyctein, arginine, tyrosine, glutamine, asparagine, proline, and glycine.
Production, formation, and manufacture
In the human body, adiuretin is produced along with oxytocin in the hypothalamus, an area of the diencephalon near the optic nerves. It is then released into the bloodstream. The amount of ADH that is released is determined by the osmotic concentration of the blood. The water balance of the human body is regulated by osmosis – the balance between the particles of a fluid through a semipermeable membrane. If water is lacking in the human body, increased adiuretin is released. Sensors are located in the hypothalamus that detect and transmit the osmotic concentration. Blood pressure also plays a major role in regulating the amount of ADH released – the corresponding sensors are located in large blood vessels.
Function, action, and properties
The most important function of ADH is the regulation of water balance. The hormone causes water to be returned to the body via receptors on the collecting tubes of the kidneys. This increases the concentration of urine while its quantity decreases. In healthy people, this process is particularly evident at night, as sleeping through the night without urinating is possible without any problems. Adiuretin also fulfills other functions. For example, in larger quantities it causes blood vessels to constrict, resulting in an increase in blood pressure. In the liver, the hormone causes the release of sugar into other organs (glycolysis). This need occurs when the body has an increased energy demand, in which the sugar from food is not sufficient to supply the cells optimally. Some of the adiuretin does not make its way into the bloodstream, but travels to the anterior pituitary gland. There it causes the release of ACTH (adrenocorticotropin). This peptide hormone causes the release of endogenous cortisol (glucocorticoids) in the adrenal gland and is thus also responsible for the release of insulin. Since ADH is at the beginning of this chain, it is thus also one of the components of the hormonal stress mechanism.
Diseases, ailments, and disorders
Disorders in the production of ADH can manifest as both overproduction and underproduction, with the latter being much more common. In diabetes insipidus centralis, the organism has too little ADH. There are many reasons for this. A missing or too low production of adiuretin or a missing transport to the posterior pituitary lobe can be responsible as well as an insufficient storage in the hypothalamus or the missing transport to the body cells. The consequences are the same in all cases, as no or too little ADH arrives at its target to exert its effect. The main symptoms consist of increased urine output and severe thirst. Affected individuals lose urine without drinking much. Additional symptoms may include dry skin, sleep disturbances, irritability or constipation. The disease can be diagnosed by laboratory tests, especially the thirst test: the patient undergoes laboratory tests after several hours without fluid intake. A healthy person will show an increase in ADH due to thirst, which cannot be recorded in a sick person.A rare disorder associated with adiuretin consists of an overproduction of the hormone – Schwartz-Bartter syndrome. There is an excess of water in the organism, causing affected individuals to gain a lot of weight. In addition, the blood is thinned, so that symptoms occur due to the low concentration of sodium. Drowsiness, headaches or a feeling of being uninvolved are the consequences. Dilution of the blood is often detected by routine examination. In addition, a urinalysis may detect excessive concentration of urine. In both cases, the causes are extremely varied. They are often benign or malignant tumors of the hypothalamus, cerebral hemorrhage after accidents, vascular inflammation, a cyst, or more rarely granulomatosis. In most cases, the condition can be well treated by eliminating the underlying problem.
