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Peshawar Medical College NWFP Pakistan Phosphorus Peshawar Medical College NWFP Pakistan Learning Objectives • Dietary sources • Daily Requirements • Metabolism • Important functions and • Deficiency diseases Peshawar Medical College NWFP Pakistan Phosphorous P At. No. 15 Atomic Mass: 30.77 Peshawar Medical College NWFP Pakistan PHOSPHORUS Peshawar Medical College NWFP Pakistan Dietary Source • Present in all foods, Dietary deficiency is therefore unknown. • Distribution is similar to Ca++ . Adequate, intake of one ensures that of the other. • Best sources (Milk and milk products) • Lean meat is also a good source. Peshawar Medical College NWFP Pakistan Recommended Dietary Allowance Infants Children Up to 6 months 240 mg 6 m – 1.0 year 360 mg 1–3 800 mg 4–6 800 mg 7 – 10 800 mg Peshawar Medical College NWFP Pakistan Recommended Dietary Allowance Adults (Male/Females) 11 – 14 1200 mg 15 – 18 1200 mg 19 – 22 800 mg 23 – 50 800 mg 51+ 800 mg Pregnant and lactating women should take an additional 400 mg. Peshawar Medical College NWFP Pakistan Absorption and Metabolism • Normally about 70% of dietary P is absorbed (For calcium 10 – 30%) • Mid jejunum is the main site of absorption for free PO4 . • In ileum absorption occurs via active process. Peshawar Medical College NWFP Pakistan Absorption and Metabolism • Most of phosphorus in food is in combined form, absorption requires splitting off of PO4 by intestinal enzymes (Phosphatases) • is hydrolyzed in GIT by Pancreatic & intestinal enzymes. Peshawar Medical College NWFP Pakistan Absorption and Metabolism • Inorganic phosphorus is released and absorbed • Its absorption decreases during period of increased utilization of carbohydrate Peshawar Medical College NWFP Pakistan Factors affecting absorption • Similar to Calcium like: • Enhancement by Vit D and • Inhibition by binding agents i.e. Iron and Aluminium. • Ca : P ratio in diet. • Excess of one causes, an increased excretion of other. Peshawar Medical College NWFP Pakistan Ratio of P : Ca • Ideal 1 : 1 , Specially during the period of rapid growth (childhood), pregnancy and lactation. • Ratio in other age groups if different, have no serious adverse effect Peshawar Medical College NWFP Pakistan In Infants • Care should be exercised as kidneys can’t handle high phosphate load. • For Prevention of hypocalcemic tetany Ca : P ratio be 1.5 : 1 • Ratio should be reduced to 1:1 by age 1 yr Peshawar Medical College NWFP Pakistan Distribution • Phosphorus accounts for about 1% of TBW. • ¼th of total body mineral matter • 80 – 90% joined with Ca++ in bones and teeth (Ratio 2:1) as a component of calcium phosphate and is being constantly deposited and liberated from bone structure. • 10 – 20% present in all cells as phosphate ion (PO=4) Peshawar Medical College NWFP Pakistan Functions • Component of many compounds involved in many metabolic reactions. • Sugar – PO4 linkage in DNA and RNA • Phospholipids Transport of fat in blood • Phospholipids cell membrane control transport of substances into and out of cell Peshawar Medical College NWFP Pakistan Functions • Phosphorylation • Necessary for glucose absorption from intestine • Glucose uptake by individual cells • Resorption of glucose by kidney Peshawar Medical College NWFP Pakistan Functions • Monosaccharides are Phosphorylated several times during metabolic break down to yield energy. • Involved in storage and release of Energy through high energy phosphate bond of ATP and ADP. Peshawar Medical College NWFP Pakistan Functions • Essential part of body’s delicate buffer system • Many B vitamins becomes active only when combine with phosphate. Peshawar Medical College NWFP Pakistan Hypo-Phosphatemia a. Diminished Supply: • Starvation • Malnutrition • Vit D – Deficiency b. Increased excretion / loss • Hyperparathyroidism • Hyper thyroidism • Renal defects Peshawar Medical College NWFP Pakistan Hypo-Phosphatemia c.Intracellular shift of phosphorus • Glucose induced • Insulin induced • Respiratory alkalosis d.Electrolytes administration • Hypercalcaemia • Hypomagnesimia Peshawar Medical College NWFP Pakistan Hyper-Phosphatemia 1. Endocrine disease – Increased growth hormones (acromegaly) – Hypo parathyroidism low calcium – Pseudo hypo parathyroidism 2. Renal Diseases • Chronic renal insufficiency • Acute renal failure Peshawar Medical College NWFP Pakistan Hyper-Phosphatemia 3. Catabolic states • Stress or injury • Chemotherapy for malignant disease 4. Excess intake or Absorption • Laxatives or Enemas containing phosphate • Hyper vitaminosis – D Peshawar Medical College NWFP Pakistan Excretion • Phosphate level is regulated by urinary excretion • 2 mg / dl is the renal thresh hold • 500 mg / day is excreted in urine Peshawar Medical College NWFP Pakistan Excretion • General factors affecting intestinal absorption • Plasma concentration and Hydrolysis of PO4 esters by phosphatases in the kidney. • Decrease Ca++ intake will increase urinary PO4 excretion Peshawar Medical College NWFP Pakistan Clinical Importance Peshawar Medical College NWFP Pakistan
