Calcium In The Body: Distribution, Normal Levels, And Hormonal Control

Calcium In The Body: Distribution, Normal Levels, And Hormonal Control

Write an essay on distribution, normal level and hormonal control of plasma calcium and phosphorous.
Answer:

1. Calcium:

Distribution:

• Calcium is present in three forms.
  • Ionized or diffusible calcium- 50%.
    • It is found freely in the plasma.
    • It is essential for vital functions.
  • Non-ionized or non-diffusible calcium- 8-10%.
    • Present as calcium bicarbonate.
    • Calcium bound to albumin – 40-42%.

Normal level:

• Normal serum calcium is 9-11 mg/dl.

Hormonal control:

• Calcium concentration is regulated by the action of following hormones.
  • Vitamin D.
    • It increases serum calcium level by.
    • Increasing Ca2⁺ from the small intestine
    • Stimulates osteoclasts to mobilize Ca2⁺ into ECF from bones.
    • Increases reabsorption of Ca2⁺ from renal tubules.
  • Parathormone (PTH).
    • Increases plasma Ca2⁺ by promoting bone resorption.
    • Increases reabsorption of Ca2⁺ from renal tubules and decreases its excretion
    • Increases calcium absorption from gut.
    • Decreases the amount of Ca2⁺ secreted in the milk.
  • Calcitonin:
    • Inhibit osteoclasts activity.
    • Inhibits intestinal absorption of Ca2⁺

2. Phosphorous:

• Distribution:
  • 80-85% – In skeleton
  • 15-20% – In intracellular phosphate pool.
• Value:
  • In adults 2.5-4 mg/dl.
  • In children – 5-6 mg/dl.
• Hormonal control:
  • Phosphate level is regulated by
• Vitamin D:
  • Increases PO₄^3- absorption from GIT.
  • Has osteolytic activity on bones.
  • Increases reabsorption of phosphate ions from renal tubules.
• Parathorome – PTH:
  • Decreases PO₄^3- level by its osteoclastic activity.
  • Decreases renal reabsorption of PO₄^3- and increases its excretion.
  • Increases PO₄^3- absorption from GIT.