Calcium homeostasis

  1. Largest store of bodily calcium?
    Contained within the skeleton
  2. Calcium levels are primarily controlled by? & small roles?
    Parathyroid hormone (PTH), vitamin D and calcitonin.

    Both growth hormone and thyroxine also play a small role in calcium metabolism.
  3. Actions of PTH? (7)
    • ncrease calcium levels and decrease phosphate levels
    • - Increases bone resorption
    • - Immediate action on osteoblasts to increase ca2+ in extracellular fluid
    • - Osteoblasts produce a protein signaling molecule that activate osteoclasts which cause bone resorption
    • - Increases renal tubular reabsorption of calcium
    • - Increases synthesis of 1,25(OH)2D (active form of vitamin D) in the kidney which increases bowel absorption of Ca2+
    • - Decreases renal phosphate reabsorption
  4. Active form of vit D?
  5. Actions of 1,25-dihydroxycholecalciferol ((the active form of vitamin D)?
    • - Increases plasma calcium and plasma phosphate
    • - Increases renal tubular reabsorption and gut absorption of calcium
    • - Increases osteoclastic activity at high levels and osteoblasts at low levels
    • - Increases renal phosphate reabsorption
  6. Calcitonin actions?
    • - Secreted by C cells of thyroid
    • - Inhibits intestinal calcium absorption
    • - Inhibits osteoclast activity
    • - Inhibits renal tubular absorption of calcium
Card Set
Calcium homeostasis
Calcium homeostasis