Minerals- CA Mg & P

8/3/2019 Minerals- CA Mg & P

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D R . C Y R I L J A C O BK U R I A N


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Sources

Milk

Egg, fish, vegetables

Cereals

Daily requirements

Adult : 500mg/dayChildren : 1200mg/day

Pregnancy and lactation : 1500mg/day

Calcium


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Occurs in the first and second part of

duodenum

Absorption requires a carrier protein, helpedby Calcium dependent ATPase

Factors increasing absorption Vitamin D which induces synthesis of the carrier protein

Calbindin in the intestinal epithelial cells Parathyroid hormone increases calcium transport from

intestinal cells

Acidity favors calcium absorption

Amino acids, especially lysine and arginine

Absorption of Calcium


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Factors decreasing Calcium absorption Phytic acid present in cereals

Oxalates present in some leafy vegetables

In malabsorption syndromes causing steatorrhoea, fattyacid is not absorbed, causing formation of insoluble saltsof fatty acid

High phosphate content will cause precipitation ascalcium phosphate


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1. Activation of enzymes

2. Contraction of muscle fibres3. Transmission of nerve impulses

4. Calcium- calmodulin complex regulatesmicrofilament mediated processes such as

degranulation of secretary vesicles,endocytosis, cell motility etc.

Functions of Calcium


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5. Secretion of hormones such as insulin,parathyroid hormone etc. from the

endocrine cells.6. Calcium and cAMP are second messengers

of different hormones. E.g. glucagon

7. Permeability of serum through capillaries isdecreased by calcium

8. Calcium is known as factor IV in bloodcoagulation cascade

Functions of Calcium


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9. In myocardium, calcium prolongs systole

10. Bulk of calcium is used for bone and teethformation


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Normal blood level of calcium is 9-11mg/dl

Blood levels of Calcium


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Factors Regulating Blood Calcium

Levels


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Effects on Vitamin D Parathormone Calcitonin

Blood

Calcium

Increased Much increased Decreased

Intestine Increased Increased (indirectly)

Bone Increasesbone formation Demineralization Opposesdemineralizaton

Kidney Increased calcium

reabsorption and

increased phosphateexcretion

Increased

phosphate

excretion

Deficiency

manifestation

Rickets Tetany


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Other factors affecting serum calcium include Phosphorus

Serum proteins

Acid and alkali

Renal threshold, etc.


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Blood calcium more than 11mg/dlMajor cause is hyperparathyroidism caused

by a parathyroid adenoma or an ectopicparathormone secreting tumor.Clinical signs include osteoporosis, punched

out areas on X-ray, pathological fractures,

polyuria, bilateral recurrent renal calculi,ectopic calcification in arterial walls, muscletissues etc., anorexia, muscle wealness andshort QT interval on ECG.

Hypercalcemia


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Serum calcium


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X-linked dominant condition

Although PTH level is normal, there is

abnormal end organ response to PTH.This leads to hypocalcemia and

hyperphosphatemia

Shortening of 4th and 5th metacarpal and

metatarsal bones may be associated

Pseudohypoparathyroid

ism


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Defective H production in the renal tubules

Kidney cannot lower urinary pH below 5

Excess urinary loss of bicarbonate, sodium,potassium, calcium, magnesium andphosphates. Serum calcium and bicarbonate

levels are lowered.Bone changes are similar to rickets, so often

called Renal Rickets.

Renal Tubular Acidosis+


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Glucosuria and aminoaciduria are associated withhypercalciuria and hyperphosphturia. Consequently,

serum calcium levels are lowered.

Fanconi's Syndrome


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Mainly an intracellular ion

Functions of phosphate ions are:1. Formation of bones and teeth

2. Production of high energy phosphate compounds likeATP,GTP,CTP,creatine phosphate etc.

3. Synthesis of nucleside co-enzymes likesuch as NAD

and NADP4. DNA and RNA synthesis ,where phosphodiester

linkages form the backbone of the structure

Phosphorus


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5. Formation of phosphate esters likeglucose-6-phosphate, phosphoproteins

and phospholipids6. Activation of enzymes

7. Phosphate buffer system in blood

Serum phosphate level is 3-4mg/dl innormal adults and 5-6mg/dl in children

Requirement is 500mg/day

Surces include milk, cereals, nuts and meat


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Mainly an intracellular ion

Requirement

400mg/day Men300mg/day Women

Sources

Cereals, beans, leafy vegetables and fish

Normal serum magnesium level is 1.8 - 2.2mg/dl

Magnesium


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Functions of Magnesium: Activator of enzymes

Lowers neuromuscular irritability Improves glucose tolerance

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Minerals- CA Mg & P