1. Calcium & Inorganic phosphate

2. Calcium Physiological function : Bone mineralization Blood coagulation Important in muscle contraction Affecting enzyme activity Affecting hormone secretion

3. Regulation of Ca metabolism

4. Distribution of Ca 99% of calcium in the body is part of bone. 1% in the blood : - 45% circulates as free Ca ions - 40% bound to albumin - 15% bound to anions ► Both total calcium and ionized calcium measurements are available in many laboratories. ► Ionized calcium is usually a more sensitive and specific for calcium disorders.

7. Determination of Ca Specimen: serum or lithium heparin plasma Anticoagulants such as EDTA or oxalate bind Ca very tightly and interfere with its measurement Methods: ( For total Ca ) - Photometric Methods - Atomic Absorption spectrophotometric methods

8. Corrected [Ca] = measured [Ca] + 0.02 ˣ ( 40 – [albumin] ) Methods: ( for Free Ca ) Calcium ion-selective electrodes

9. Phosphate Physiological function : 80% of the total body phosphate is contained in bone. High-energy phosphate bond in ATP Essential element in - Phospholipid cell membranes - Nucleic acids - Phosphoproteins Phosphate is critical for activity for several important enzyme

10. Regulation: PTH lowers blood phosphate concentrations by Increasing renal excretion. Vitamin D acts to increase phosphate in the blood due to - Increase phosphate absorption in the intestine - Increase phosphate reabsorption in the kidney Clinical Application: - Hypophosphatemia - Hyperphosphatemia

11. Hypophosphatemia Hypophosphatemia is very common in hospitalized patients Infusion of dextrose solution Use of antacids that bind phosphate Alcohol withdrawal Hyperphosphatemia Renal failure : ↓ phosphate excretion Neonates are susceptible to hyperphosphatemia Increased breakdown of cells eg: - severe infections - neoplastic disorders

12. Determination of inorganic phosphorus Specimen: serum or lithium heparin plasma hemolysis should be avoided Methods: Formation of an ammonium phosphomolybdate complex - measured at 340 nm - can be reduced to form molybdenum blue (measured at 660 nm)