Potassium Homeostasis

Overview (NEJM 2015;373:60)

  • Renal: K excretion regulated at distal nephron (CCD) by principal & α-intercalated cells
    • Distal Na delivery & urine flow: Na absorption → lumen electronegative → K secretion
    • Metabolic alkalemia and aldosterone: increase Na absorption and K secretion
    • nb, diurnal urinary K excretion (day > night), ∴ 24-h sample preferred over spot
  • Transcellular shifts: most common cause of acute ∆ in serum K (98% intracellular)
    • Acid-base disturbance: K+/H+ exchange across cell membranes
    • Insulin → stimulates Na-K ATPase → hypokalemia (mitigates postprandial ↑ K)
    • Catecholamines → te Na-K ATPase → hypokalemia; reversed by β-blockers