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MLAB 2401: Clinical Chemistry Keri Brophy -Martinez. Overview: Mineral and Bone Metabolism. Calcium Homeostasis . Organs involved Small intestine Skeleton Hydroxyapatite ( calcium+ phosphorus+ hydroxide) Kidneys Origin Diet Reservoir Bone. Forms of Calcium. Bound to albumin–45%

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mlab 2401 clinical chemistry keri brophy martinez

MLAB 2401: Clinical ChemistryKeri Brophy-Martinez

Overview:

Mineral and Bone Metabolism

calcium homeostasis
Calcium Homeostasis
  • Organs involved
    • Small intestine
    • Skeleton
      • Hydroxyapatite
        • ( calcium+ phosphorus+ hydroxide)
    • Kidneys
  • Origin
    • Diet
  • Reservoir
    • Bone
forms of calcium
Forms of Calcium
  • Bound to albumin–45%
    • Reversible process
    • Binding is pH dependent
  • Free “ionized”–50%
  • Complexes with anions -5%
ionized calcium
Ionized Calcium
  • Free calcium in blood
  • Tightly regulated
  • Biologically active form
  • Advantage
    • Not associated with proteins or anions
functions of calcium
Functions of Calcium
  • Nerve impulse transmission
  • Cofactor in certain enzymes
  • Coagulation of blood
  • Skeletal mineralization
  • Preservation of cell membrane integrity and permeability
regulation of calcium homeostasis
Regulation of Calcium Homeostasis
  • Parathyroid hormone- PTH
  • Vitamin D3
  • Calcitonin
parathyroid hormone pth
Parathyroid Hormone- PTH
  • Originates from the parathyroid gland
  • Secretion based on levels of free calcium
  • Activities/Roles
    • Stimulation of osteoclastic bone reabsorption and release of calcium and phosphate from bone
    • Stimulation of calcium reabsorption and inhibition of phosphate reabsorption from the renal tubules
    • Stimulation of renal production of 1,25(OH)2 vitamin D3, which increase intestinal absorption of calcium and phosphate
vitamin d 3 cholecalciferol
Vitamin D3/ Cholecalciferol
  • Synthesis occurs in skin, liver, kidneys
  • Affects gut, bone, and parathyroid
  • Actions/ Roles
    • Increases plasma calcium and phosphate concentration by increasing the absorption of calcium and phosphate from the gastrointestinal tract
    • Increases bone resorption and enhances the effects of PTH in the nephron to promote renal tubular calcium reabsorption
    • Stimulates osteoclasts to metabolize bone calcium
vitamin d where does it come from
Vitamin D: Where Does it Come From?
  • Sources of:
    • Diet
      • Animal tissues and products ( liver)
      • Irradiated milk
    • Sunlight
calcitonin
Calcitonin
  • Secreted by the thyroid gland
  • Secreted when blood calcium rises
  • Inhibits PTH and Vitamin D
  • Inhibits bone resorption, promotes bone formation
phosphorous
Phosphorous
  • Origin
    • Diet
    • Bone
    • Phosphate ion is distributed equally.
      • Intracellular
        • Component of macromolecules
      • Extracellular
  • Inverse relationship with Calcium
functions of phosphorous
Functions of Phosphorous
  • Component of bones & teeth
  • Essential part of cell membranes
  • Contributes to enzyme function
  • Storage and transfer of energy
  • Component of many compounds
phosphorous regulation
Phosphorous Regulation
  • Kidneys
    • Excrete or reabsorb
  • Other factors
    • PTH
      • Increases renal excretion
    • Vitamin D increases levels
      • Phosphate absorption in intestine
      • Phosphate reabsorption in kidneys
    • Growth Hormone, calcitonin, acid-base status
magnesium
Magnesium
  • 2nd most abundant intracellular cation
  • Location
    • 50-60% found in bone
    • 40-50% muscle & soft tissue
    • 1% in the RBC
  • Origin
    • Diet
      • Nuts, hard water, meat, green vegetables, fish, dry cereal
forms of magnesium
Forms of Magnesium
  • Free or ionized (~55%)
  • Bound to proteins (~30%)
  • Complexed with phosphate, citrate and other ions (~15%)
functions of magnesium
Functions of Magnesium
  • Important co-factor in reactions using ATP
    • Carbohydrate metabolism
    • Muscle contraction
    • Blood coagulation
  • Membrane stabilization
  • Nerve conduction
  • Maintenance of potassium
magnesium regulation
Magnesium Regulation
  • Primary regulatory factor
    • Amount of magnesium in the plasma
  • Regulatory control
    • Kidney
      • Excrete or reabsorb magnesium depending on condition
    • Parathyroid hormone
      • Increases renal reabsorption
      • Enhances absorption in intestines
references
References
  • Bishop, M., Fody, E., & Schoeff, l. (2010). Clinical Chemistry: Techniques, principles, Correlations. Baltimore: Wolters Kluwer Lippincott Williams & Wilkins.
  • http://rickets.stanford.edu/
  • http://scrink.com/blog/wellness/2009/02/vitamin-d-cold-flu-correlation.html
  • Sunheimer, R., & Graves, L. (2010). Clinical Laboratory Chemistry. Upper Saddle River: Pearson .