Describe the endocrine functions of the kidney.

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College Answer

It was expected that candidates would discuss the major hormones produced (or activated) by the kidney. These included erythropoeitin, renin and calcitriol. Good answers included the following: the area where the hormone is produced or modified; stimuli for release; factors which inhibit release; and the subsequent actions / effects. Marks were not awarded for hormones that act on the kidney


  • Hormones which are secreted by the kidney
    • Erythropoietin
      • Secreted from modified cortical fibroblasts
      • Stimulated by hypoxia and angiotensin II
      • Inhibited by inflammatory cytokines
      • Effect is increase in the rate of red cell production and maturation
    • Renin
      • Secreted from juxtaglomerular cells
      • Stimulated by hypotension, sympathetic activation and decreased renal salt delivery
      • Inhibited by angiotension II and normalised blood pressure/volume
      • Effect is to activate RAAS, producing vasoconstriction and salt/water retention
    • Thrombopoietin
      • Secreted from the proximal convoluted tubule
      • Stimulated by thrombocytopenia and inflammatory cytokines
      • Inhibited by itself (negative feedback loop)
      • Effect is to stimulate megacaryocytes and increase platelet production
    • Urodilatin
      • Secreted from DCT cells, directly into the tubule
      • Stimulated (probably) by increased sodium delivery
      • Inhibited (presumably) by decreased sodium delivery
      • The effect to increase sodium reabsorption in the collecting duct
  • Hormones which are modified by the kidney
    • Calcitriol (active form of Vitamin D)
      • Modified in the proximal tubule
      • Increased  conversion is stimulated by hypocalcemia, PTH and low vitamin D levels
      • Conversion is inhibited by hypercalcemia, low PTH and high vitamin D levels
      • Physiological role is to increase calcium levels by increasing renal/GI absorption and enhancing osteoclast activity
  • Hormones which are cleared or metabolised by the kidney
    • Insulin
      • 90% cleared by the kidney (proximal tubule)
    • Gastrin
      • 30% cleared by the kidney (probably also proximal tubule)
    • Other hormones:
      • PTH
      • Vasopressin
      • Oxytocin
      • TSH
      • Growth hormone
      • Luteinising hormone


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