Aside from regulating extracellular fluid volume, electrolyte concentrations, and acid-base balance, the kidney has also a secretory functions. Its secretions are very important in the formation of red blood cells and regulating blood pressure. The following are the hormones produced by the kidney:
Erythropoietin. Along with vitamin B12, it estimulates the bone marrow to produce red blood cells.
Renin. It is an enzyme which increases blood pressure, activating angiotensin, which a vasoconstrictor plasma protein that also estimulates the adrenal cortex.
Relaxin. It makes a woman's pelvic ligaments relax and the cervix dilate during childbirth.
Thrombopoietin. It induces the megakaryocytes to produce platelets.