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MLAB 2401: Clinical Chemistry Keri Brophy-Martinez Overview: Mineral and Bone Metabolism.

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Presentation on theme: "MLAB 2401: Clinical Chemistry Keri Brophy-Martinez Overview: Mineral and Bone Metabolism."— Presentation transcript:

1 MLAB 2401: Clinical Chemistry Keri Brophy-Martinez Overview: Mineral and Bone Metabolism

2 Calcium Homeostasis Organs involved ◦ Small intestine ◦ Skeleton  Hydroxyapatite  ( calcium+ phosphorus+ hydroxide) ◦ Kidneys Origin ◦ Diet Reservoir ◦ Bone

3 Forms of Calcium Bound to albumin–45% ◦ Reversible process ◦ Binding is pH dependent Free “ionized”–50% Complexes with anions -5%

4 Ionized Calcium Free calcium in blood Tightly regulated Biologically active form Advantage ◦ Not associated with proteins or anions

5 Functions of Calcium Nerve impulse transmission Cofactor in certain enzymes Coagulation of blood Skeletal mineralization Preservation of cell membrane integrity and permeability

6 Regulation of Calcium Homeostasis Parathyroid hormone- PTH Vitamin D 3 Calcitonin

7 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 D 3, which increase intestinal absorption of calcium and phosphate

8 Regulation of Calcium Homeostasis

9 Vitamin D 3 / 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

10 Vitamin D: Where Does it Come From? Sources of: ◦ Diet  Animal tissues and products ( liver)  Irradiated milk ◦ Sunlight


12 Calcitonin Secreted by the thyroid gland Secreted when blood calcium rises Inhibits PTH and Vitamin D Inhibits bone resorption, promotes bone formation

13 Phosphorous Origin ◦ Diet ◦ Bone ◦ Phosphate ion is distributed equally.  Intracellular  Component of macromolecules  Extracellular Inverse relationship with Calcium

14 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

15 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

16 Magnesium 2 nd 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

17 Forms of Magnesium Free or ionized (~55%) Bound to proteins (~30%) Complexed with phosphate, citrate and other ions (~15%)

18 Functions of Magnesium Important co-factor in reactions using ATP ◦ Carbohydrate metabolism ◦ Muscle contraction ◦ Blood coagulation Membrane stabilization Nerve conduction Maintenance of potassium

19 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

20 References Bishop, M., Fody, E., & Schoeff, l. (2010). Clinical Chemistry: Techniques, principles, Correlations. Baltimore: Wolters Kluwer Lippincott Williams & Wilkins. flu-correlation.html flu-correlation.html Sunheimer, R., & Graves, L. (2010). Clinical Laboratory Chemistry. Upper Saddle River: Pearson.

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