article- -4. Endocrine Functions of the Kidneys • Functions of Cells and Human
"The kidneys secrete a variety of hormones, including erythropoietin, calcitriol, and renin. Erythropoietin is released in response to hypoxia (low levels of oxygen at tissue level) in the renal circulation. It stimulates erythropoiesis (production of red blood cells) in the bone marrow. In addition to synthesis , the kidneys also contribute to the degradation of certain hormones – such as insulin (forms insulinase – cleaves insulin) or parathyroid hormone."
source: fblt.cz/en/skripta/vii-vylucovaci-soustava-a.../4-endokrinni-funkce-ledvin/