Formation of ADH: ADH, which is also called antidiuretic hormone, adiuretin or vasopressin, is a peptide hormone. This hormone is produced together with the carrier protein neurophysin II in special nuclei of the hypothalamus (nucleus supraopticus, nucleus paraventricularis). The hormone is then stored in the posterior lobe of the pituitary gland, where it is released into the bloodstream as required.
The breakdown of ADH takes place in the liver. V1 and V2 receptors matching the hormone are located on the cell surface of the target cells. Regulation of ADH: The amount of the hormone ADH is regulated by serum osmolality and blood pressure.
Osmolality is the amount of osmotically active particles in a fluid, in this case in the blood. Osmotically active means that the particles react according to the principle of osmosis, which means that particles move across a membrane due to different concentrations on both sides of the membrane. The particles move with the aim of producing the same amount of particles per unit of liquid on each side (concentration).
Alternatively, if the membrane is impermeable to the particles, water flows from one side to the other for dilution, as the membrane usually allows this to pass. An increase in osmolality results in increased ADH release. Osmolality is measured via osmoreceptors, which are mainly found in the hypothalamus.
In addition, baroreceptors for measuring blood pressure are located at certain points of large blood vessels – namely in the carotid sinus and aortic sinus. Volume receptors are located in the atria of the heart. These two types of receptors enable the regulation of blood pressure via coupled ADH release.
ADH as the second component of these hormones affects the blood vessels, the sugar metabolism, via the kidneys the water balance and the anterior pituitary gland. At the vessels, the hormone ADH has a constrictive effect (vasoconstriction), which results in an increase in blood pressure. In the liver, the hormone forces the sugar stores to be emptied (glycogenolysis), thus releasing sugar into the blood.
Furthermore, ADH has a blood pressure-lowering effect on the portal vein system of the liver (blood vessel system). In the kidneys, this hormone acts on the so-called collecting pipes (structures for the drainage of urine) by increasing the body’s reabsorption of water through the installation of water channels (aquaporins) and thus reducing water excretion by lowering the amount of urine. Instead, the urine is less diluted, so that the osmolality increases.
Alcohol causes an inhibition of ADH secretion. This leads to the diuretic effect of alcohol. Without the hormone ADH, a lot of water or urine is excreted, which is called diuresis.
