Endocrine Function of the Human Kidney

The endocrine system refers to the different organs of the body that are responsible for secreting hormones that affect bodily processes. Better known for their ability to process waste, the kidneys are responsible for the secretion of four different hormones: rennin, calcitriol, erythropoietin and thrombopoietin. These chemicals released by the kidneys affect a wide range of bodily processes dealing with the circulatory and skeletal systems. Understanding the endocrine functions of the kidneys is necessary to understand the full impact the kidneys have on the body.

Rennin

• Rennin is a proteolytic enzyme responsible for regulating arterial wall size to ensure proper blood pressure. Proteolytic enzymes are capable of breaking down proteins into a more usable form. Renin breaks down the plasma protein angiotensinogen into a peptide containing ten amino acids called angiotensin I. Angiotensin I later gets broken down by a lung-based peptidase known as angiotensin converting enzyme, or ACE. The new eight-amino acid peptide, angiotensin II, increases blood pressure by increasing pulse strength and constricting vein and arterial walls.

Erythropoietin

• Erythropoietin, or EPO, is a glycoprotein that regulates the transfer of oxygen and nutrients through the bloodstream by increasing red blood cell production in the bone marrow. EPO production is stimulated when blood is lost through a wound or when less oxygen is available, such as higher altitudes. Recombinant EPO can be used as a treatment for those suffering from anemia, a deficiency of red blood cells.

Thrombopoietin

• Thrombopoietin, or TPO, increases the body's ability to heal itself by stimulating the production of platelets. Thrombopoietin is a cytokine, a protein involved with immune system functioning. TPO that has been secreted into the bloodstream bonds either with platelets or with megakaryocytes, the precursor to platelets. When the body's platelet count is high, excess TPO bonds with the platelets, decreasing production. If the platelet count is low, TPO bonds with megakaryocytes which then mature into platelets.

Calcitriol

• Calcitriol, also known as vitamin D3, improves the body's ability to absorb calcium. To produce calcitriol, vitamin D must be introduced into the body, either through a chemical reaction between the skin and sunlight creating calciferol, or dietary vitamin D that has been digested. Vitamin D in the body ends up being converted into calcitriol by the kidneys. Calcitriol travels to the intestines, where it enhances the body's absorption of calcium, improving skeletal health.

Chronic Kidney Disease

• Chronic kidney disease, or CKD, is most often caused by high blood pressure or diabetes. CKD prevents your kidneys from completing their basic functions, including straining toxins from the blood or releasing the previously mentioned hormones. Further complications caused by CKD include anemia, osteoporosis and increased risk of heart disease. Chronic kidney disease may persist for years, and may eventually require dialysis or a transplant.