calcium_1

calcium_1

plasma calcium
1. hormonal regulation
  1. calcitriol or 1,25 DHCC
    1. increase blood Ca level
    2. calcification, mineralization and remodeling of bone
  2. PTH
    1. increase serum Ca level
      1. sites of action
        bone
        Anmerkungen:
        decalcification of bone (by osteoclast)
        kidney
        Anmerkungen:
        reabsorption by renal tubules (most rapid action)
        intestine
        Anmerkungen:
        synthesis of calcitriol
  3. Calcitonin
    Anmerkungen:
    - opposite of PTH
    1. decrease blood Ca level
2. normal levels of
  1. bound Ca= 4-5 mg\dl
  2. ionized Ca= 5 mg\dl (active Ca)
  3. total Ca=9-11mg\dl
absorption in GI track
1. inhibiting factors
  1. high content of dietary fiber
  2. high pH in intestinal lumen
  3. free fatty acids
  4. Dietary Phosphate
  5. phytate & oxalate
2. promoting factors
  1. lysine & Arginine increased Ca absorption
  2. lactose
  3. low PH in intestinal lumen favors Ca absorption
  4. PTH
  5. Vit D (active form Calcitriol
Diatary requirments
1. adult woman
  1. 1500mg\ day
    1. postmenopausal
    2. during pregnancy & lactation
2. adult man
  1. 800 mg\day
biochemical functions
1. secretory process
2. release of hormone
3. activation of enzymes
4. membrane integrity & permeability
5. nerve impulse transmission
6. blood coagulation
7. muscle contraction
8. development of bone and teeth
diseased state
1. Hypercalcemia
  1. hyperparathyroidism
  2. Increased Alkaline Phosphatase activity
  3. Increased urinary excretion of Ca & P
  4. Formation of urinary calculi
  5. Serum Ca level increased
2. Hypocalcemia
  1. serum Ca below 7 mg/dl => TETANY
  2. Hypoparathyroidism
    1. surgical removal of parathyroid gland
    2. autoimmune disease
  3. it's a life threatening condition
3. Rickets
  1. Defective calcification of bone
  2. Serum Ca or P may be low or normal
  3. Increased activity of Alkaline Phosphatase is characteristic feature of Rickets
  4. due to Low level of Vit D in body
    Anmerkungen:
    - due to dietary deficiency of Ca and P.
4. Osteoporesis
  1. Demineralization of bone
    1. loss of bone mass
  2. Elderly people over age of sixty
    1. predominantly in postmenopausal women
  3. frequent bone fracture in elderly
  4. Occurs due
    1. less ability of formation of Calcitriol from Vit D in elderly
    2. Deficiency of sex hormone in postmenopausal women

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