Kidney hormones

Hormones produced in the kidney include

  • Calcitriol and
  • Erythropoietin

This glycoprotein hormone as a hormone of the kidney is produced in the kidney and to a small extent in the liver and brain in about 90% of adults. In the kidney, cells of the blood vessels (capillaries, endothelial cells) are responsible for production. They begin the synthesis of erythropoietin after being stimulated by the factor HIF-1 (hypoxia-inducible factor 1).

This factor is directly dependent on oxygen pressure. At low pressure, the stability of HIF-1 and thus the formation of erythropoietin increases, whereas at high pressure HIF-1 shows instability, which reduces the synthesis of the hormone. Regarding the synthesis of hormone, HIF-1 acts as a transcription factor.

Transcription of these kidney hormones means the translation of the gene structure (DNA = deoxyribonucleic acid) into proteins, in this case into the hormone erythropoietin. HIF-1 consists of two different subunits (alpha, beta). First, the alpha-subunit of HIF-1 migrates into the cell nucleus in the event of oxygen deficiency and binds to the beta-subunit there.

The complete HIF-1 binds to the corresponding site of the genetic material (DNA), where the information on the structure of the hormone erythropoietin is located, after the attachment of two further factors (CREB, p300). Through its binding, HIF-1 enables the information to be read and thus translated into a protein structure. This is how the hormone is ultimately produced.

The receptors of the hormone erythropoietin are located on the surface of immature red blood cells (erythroblasts), which are located in the bone marrow. The hormone is produced depending on the oxygen supply in the blood. If there is little oxygen (hypoxia), erythropoietin is released, stimulating the erythroblasts to mature.

This means that more red blood cells are available in the blood as oxygen carriers and counteract hypoxia through increased oxygen transport. If, on the other hand, sufficient oxygen is available, no erythropoietin is produced and the amount of red blood cells is not increased (negative feedback). Overall, the red blood cells are a marker for the oxygen saturation of the blood, since they bind oxygen with the help of the hemoglobin contained in the blood and transport it to various tissues in the bloodstream.

The erythropoietin of the kidneys and liver regulates the oxygen content of the blood. Specifically, this hormone affects the transport of oxygen in the blood by influencing the proliferation and maturation of red blood cells (erythrocytes), which transport oxygen in the blood. Erythropoietin, which is produced in the brain, is only found in the blood vessels of the brain, as it cannot leave this space due to the so-called blood-brain barrier.

Its function is not fully understood; it is assumed that it protects the nerve cells from damage in the event of oxygen deficiency (neuroprotective effect). In medicine, artificially (genetically) produced erythropoietin is used. In patients with anemia and renal failure, where the kidney is no longer able to produce the hormone itself, erythropoietin is administered to stimulate blood formation and thus eliminate renal anemia.

The hormone erythropoietin is also used to treat anemia caused by a tumor or after chemotherapy. In sports the hormone erythropoietin is also used as an illicit doping. As the quantity of red blood cells increases after taking this hormone, the oxygen transport capacity of the blood increases at the same time.

As a result, more oxygen reaches the muscles and other tissues, enabling the metabolism (for example, for muscle movement) to work more efficiently and for longer. As a result, the athletes’ performance capacity increases.