Calcium and Phosphate Metabolism Guide

Calcium and Phosphate metabolism
CONTENTS
 Introduction
 Distribution of in the body
 Functions
 Daily requirements
 Sources
o Absorption of Ca+ PO4
o Concept of Ca balance
o Factors controlling the absorption of Ca+ PO4
o Hormonal control of Ca metabolism
o Vit. D3
o PTH
o Calcitonin
o Excretion of Ca+ PO4
 Summary
1

Introduction
As dentists, it is vital for us to have a complete understanding of the general
metabolism of calcium and phosphorous as it is these minerals that help in the
formation and maintenance of the teeth and their supporting bony structure. 2 points
need to be kept in mind during the course of this discussion, (1)Ca++
metabolism is a
very complicated and controversial topic on which no definite conclusion has yet been
reached, which is acceptable by all researchers, (2) This topic deals with factors
affecting Ca++
metabolism in the body as a whole and it should not be assumed that all
these factors necessarily affect the teeth.
2

IMPORTANCE AND DISTRIBUTION OF Ca++
IN THE BODY
- The human body contains about 1kg of Ca++
of which 99% is in the skeleton and
remaining 1% in soft tissues and ECF (990gms) and (10gms).
of 990 gms in the skeleton
- 10 gms forms the readily
exchangeable Ca++
pool of bone
(MISCIBLE POOL)
- 980 gm  slow exchange of
Ca++
takes place (STABLE
POOL)
10.0-10.5mg/dl
NORMAL SERUM
CALCIUMLEVEL
Remaining in
soft tissues
Diffusible/ ultrafilterable form
5.5mg/dl
Non-diffusible / protein bound form
4.5mg/dl
Ionized Ca
5.0mg/dl
Bound to PO4,
HCO3, Citrate
0.5mg/dl
Bound to albumin
4.0mg/dl
Bound to
globulin
0.5mg/dl
3
10gms

FUNCTIONS OF CALCIUM
1. Contributes to hardness of bone and is a major component of teeth.
2. Stabilises the cell membrane and their permeability.
3. Maintenance of excitability of nerve and muscles.
4. Normal skeletal and cardiac muscle contraction.
5. Helps in the neurotransmitter release.
6. Secretion of granular material from exocrine and endocrine glands.
7. Hormone release and activity – discharge of non-adrenaline in the nerve terminal
cell.
8. Synthesis of nucleic acid and protein.
9. Blood coagulation – Ca++
is required for the conversion of many inactive enzymes
in the coagulation process.
DAILY REQUIREMENTS OF CALCIUM (WHO estimate)
6 months – 2 year = 0.5-0.6 g/day
1200 mg/day
16 years to adults = 0.5-0.6g/day
Pregnancy and lactation = 1.0-2gm/day
Children = 800mg/day
SOURCES OF CALCIUM AND PHOSPHOROUS
- Milk + milk products.
- Egg.
- Meat
- Fish
- Leafy vegetables
4

- Hard water
PHOSPHOROUS
DISTRIBUTION OF PHOSPHOROUS IN THE BODY
- The human body contains 500-600 gms of PO4
--
out of which 85% (425g) is in the
bone.
- Remaining phosphorous is present in the liver, pancreas and brain.
- Phosphorous is essential for the formation of teeth. Normal serum PO4
--
level is 2.5
– 4.5 mg/dl.
Serum inorganic form Organic phosphorous
3-4 mg/dl in adults remaining in the form of phospholipids &
glycerophosphates
5-6mg/dl in children
FUNCTIONS OF PHOSPHOROUS
1. Formation of bone and teeth. It is the essential constituent of all cells.
2. Important constituent of high energy phosphate compounds like ATP,
creatine phosphate, cyclic AMP, hexose phosphate, 2-3DPG,
phospholipids, nucleotides.
3. Helps in the regulation of glycolysis.
4. Phosphorylation of lipids and sugar i.e. absorption, transportation and
metabolism.
5. Urinary buffer, which regulates urinary pH.
5

CONCEPT OF CALCIUM BALANCE
Daily Requirements Of Phosphorous = 1gm/day
This term is used to describe the amount of Ca++
either stored or lost by the body over a
specific period of time. This can be calculated by deducting the amount of Ca in the urine
from the Ca taken in the diet.
Ca in diet - Ca in fasces  Ca absorbed – Ca in urine
Ca lost / gained
e.g., If 1.0gm Ca is in the diet – 0.7 gm in fasces  0.3g absorbed. 0.1g net gain  0.2g
in urine
The Ca balance values are said to change with age.
 In a growing child, there is a Net gain for growing and mineralizing skeleton.
- In an aging adult, there is a Net loss as Ca from bone is lost too due to conditions
like osteoporosis. Hence, amount of Ca lost is greater than Ca in intake.
ABSORPTION OF CALCIUM AND PHOSPHOROUS
It is seen that almost all the food taken in three the diet is almost completely absorbed
in the gut whreas the amount of minerals absorbed is very negligible.
 This could be due to the various factors affecting the absorption of Ca++
and PO4
--
.
 The factors can be studied under:
Factors affecting mucosal cell Factors influencing Ca absorption in the gut
6

FACTORS INFLUENCING MUCOSAL CELLS
1. Vitamin D and Ca absorption
It is seen and proven that the active form of vitamin D or 1,25 DH CC (di-hydroxy
cholecalciferol) increases the absorption of Ca in the gut, kidney and bone.
This increase in absorption of Ca is directly related to the increased concentration
of Ca binding protein produced by increasing synthesis of mRNA.
1,25 DHCC
↓
Increases synthesis of mRNA
↓
Increases level of Ca binding protein CBP
↓
Increases Ca plasma level
2. Effect of dietary Ca intake and Ca need
 It is seen by means of experiments that the amount of Ca STORED in the body is a
factor which influences Ca absorption.
This factor can be better understood with the help of an example. e.g., Rottenson in 1938
used 2 groups of rats for his experiment
He fed 1st
group 2nd
group
0.15% Ca for 4 weeks 0.8% Ca for 4 weeks
4 weeks later he observed that
Stored - 190mg Ca was stored (↓) (↑↑) 570mg Ca was stored
7

Thus suggesting that greater the dietary intake of Ca, greater amount of Ca is stored.
In the 2nd
stage of experiment, both groups received 0.4% Ca for 5 weeks.
0.4% Ca 0.4% CA
5 weeks 5 weeks
5 weeks later ABSORBED AMOUNT
900 mg (↑↑) 600 mg (↓)
This suggested that the group with a low Ca store absorbed more Ca than the group with
the high Ca store. Thus, suggesting that the amount of Ca absorbed is directly dependent
on the amount of Ca present in the store. This kind of an adaptation mechanism is directly
under the control of formation of 1,25 DHCC.
3. Effect of pregnancy and growth
- During pregnancy, the amount of dietary Ca absorbed increases especially
in the later months of pregnancy. Half of the Ca absorbed during
pregnancy goes to the developing foetus and the remaining half is stored in
the mother’s skeleton as a reserve for lactation.
- 2 hormones are active during pregnancy
8

PLACENTAL LACTOGEN OESTROGEN
Increases Ca absorption Acts by increasing release of PTH
which increases Ca absorption indirectly.
Hence, in later stages of pregnancy
increased PTH levels are reported.
Growth Period
- During growth of children, the growth hormone levels are high. This acts
by increasing Ca absorption and reducing amount of endogenous Ca
excretion.
Parathyroid hormone
- Is one of the main hormones controlling Ca absorption. It mainly acts by
controlling the formation of 1,25 DHCC which it active form of vit. D
which is responsible for increased Ca absorption.
CALCIUM : PHOSPHOROUS RATIO  An increase in the plasma Ca level causes a
corresponding ↓ in absorption of phosphorous and vice-versa. The product of Ca and
inorganic phosphate of the blood is always constant (ratio is 2 Ca : 1 PO4).
9

II  FACTORS INFLUENCING AVAILABILITY OF CALCIUM IN THE GUT
1. pH of the intestine
• It is seen that the acids of the gastric juices dissolve most of the
Ca salts and inorganic phosphate in the diet hence allowing greater amount of Ca
available for absorption.
• In the lower part of the small intestine, the pH is said to be
more alkaline, thus causing Ca salts to undergo precipitation. Hence Ca absorption
occurs only in the upper part of the small intestine where the pH is acidic.
In patients wth achlorhydria/gastrectomy, less Ca absorption takes place.
2. Amount of dietary Ca and PO4
As discussed before, as the levels of dietary Ca and PO4 is increased, the amount
of Ca and PO4 absorbed also increases but only upto certain limit beyond which
no more absorption takes place.
This is because the active transport system in the mucosal cells can deal with only
a certain load of Ca. Once this load is exceeded, the remaining Ca is either
excreted or passively diffuses in the lower part of the gut.
This a homoestatic mechanism for preventing excessive concentration of Ca in the
blood or tissue which could have a hazardous effect.
3. Phytic acid and phytates
Are found in foods like – Oat meal
Whole wheat
Cereals
10

They are considered to be anti-calcifying factors as they combine with the Ca of
the diet thereby forming insoluble salts of Ca which are not absorbable. Hence, if
these phytates are taken in a diet, where the Ca intake is low or vit. D intake is low, it
is seen that severity of the deficiency disease worsens.
The effect of phytates is said to be quantitative and can be neutralized by adding
sufficient extra Ca to the diet.
4. Effect of Oxalates
Oxalates is another substance present in certain foods like spinach and rhubarb
leaves. These oxalates precipitate significant amounts of Ca from the diet or from
the digestive juices thereby decreasing the amount of Ca available for absorption.
Hence, it may be noticed that after eating spinach, a certain roughness can be
experienced on the surface of the teeth which is due to the precipitation and
deposition of Ca oxalate crystals (Ca from the saliva) on the teeth.
5. Effect of fat
Fat combines with Ca forming insoluble Ca soaps which decreases Ca absorption
but increases the availability of phosphorous for absorption.
Fat combines with Ca and liberates PO4 for absorption. Hence, excess fats hinders
Ca absorption but favour phosphorous absorption.
6. Effects of proteins and Aminoacids
It is seen that a considerable increase in the Ca absorption occurs with a high
protein diet.
11

Proteins and Amino acids effect Ca in 2 ways:
Proteins form soluble complexes thus
allowing Ca to remain in a form which is
easily absorbable
Protein metabolism leads to formation of
certain acids that encourages the removal
of Ca from the skeleton. Hence, urinary Ca
level increase with a richer protein diet
Hence a high protein diet may be
considered as a possible factor for
osteoporosis.
But under such conditions, the increased
absorption is of no value as this absorbed
phosphorous cannot be retained without
Ca. Hence the excess phosphorous is
quickly excreted.
7. Effect of carbohydrates
It is seen that certain carbohydrates like lactose create an acidic pH in the gut by
favouring growth of acid producing organisms. This acidic environment of gut
favours Ca absorption.
 Contradictory studies show that an increased level of Ca is seen in the body not by
increase in Ca absorbed but by decrease in Ca excreted in urine.
8. Bile salts favours Ca and phosphorous absorption as it dissolves fats thereby allowing
greater amounts of Ca+ phosphorous to be available for absorption.
12

HORMONAL CONTROL OF CALCIUM METABOLISM
 A complex set of interlocking mechanisms takes place in order to allow man to
survive major dietary Ca intake fluctuations. These mechanisms are mainly controlled by
the endocrine systems.
Three main hormones acting at 3 different sites are responsible for Ca
metabolism.
1. Vit. D3 Bone.
2. Parathormone Kidney
3. Calcitonin Intestine
1) Vit. D3 is a steroid derivative
Vit. D3 – cutaneous synthesis – important in Ca metabolism.
Vit. D2 – Ergocalciferol
Dietary source is fish, milk and eggs.
• Vit. D is also known as cholecalciferol.
• Besides dietary intake, cutaneous synthesis of vit.D. is another
important source of Vit. D in the body.
• Present within the inner layers of the epidermis, lies an enzyme
known as 7-dehydrocholesterol. UV Rays PRE VITAMIN D3
IN LIVER
Taken to kidney
Pre Vit. D3 IN LIVER 25, OH cholecalciferol (main circulating subs, but it is
relatively inactive as it is bound to  globulin.
13
Bound Binding protein (DBP) to
Vit. D and taken to liver

25-OH-CC
Undergoes
Hydroxylation by
1--hydroxylase enzyme whose
formation is under the control of PTH
1,25,
Dihydroxycholecalciferol or
calcitriol (active form of
Vit. D3 which is considered
to be a horomone)
- Daily requirements of vit. D  400 I.U.
Action of Vit. D.
Vit. D. acts on the intestine, kidney and bone thereby bringing about an increase in the Ca
absorbed. The active form of vit. D which is produced in the kidney has its action on
many tissues away from the site of its production. Hence 1,25DHCC is often known as a
hormone.
Acts mainly by increasing the synthesis of mRNA which directly increases the
concentration of (CBP) Ca binding protein mainly in the tissues of the intestinal mucosa.
The CBP thereby binds with increased amount of Ca and allows increased Ca to be
absorbed.
1. Action on the intestinal
1,25 DHCC increases the synthesis of CBP in the intestinal epithelium thereby
increasing the transportation of Ca from the intestinal lumen to the epithelium.
Hence, the amount of Ca absorbed is directly proportional to the amount of CBP
present in the mucosal cells.
2. Action the kidney
1,25 DHCC increases the amount of Ca absorbed from the renal tubules.
14

3. Action on the bone
Before studying the action of vit. D on the bone we must understand the term
Osteocytic Membrane System.
As we all know, the cells of the bone are the:
Osteocytes
Osteoblasts
Osteoclasts
The osteocytes / resting bone cells are present within the bone.
The osteoblasts / bone forming cells are found in the endosteum lining the bone.
The osteocytes and the osteoclasts communicate with each other via the long
cytoplasmic processes. Hence, the osteoblasts present outside the bone and
osteocytes present within the bone form a system of interconnected cells that
spread all over the bone suface.
This extensive system is known as osteocytic membrane system (OCM).
This system separates the bone from the E.C.F. Bone fluid is present between
bone and OCM).
Action
Vit. D. / 1,25 DHCC is said to mediate the pump that actively transports Ca from
within the OCM to the ECF thereby raising plasma Ca levels.
Deficiency of vit. D in the body either due to a deficient diet or due to insufficient
solar exposure results in disorders known as Rickets in younger children or
Osteomalacia in adults.
15

Rickets - Delayed eruption
- Malallignment of teeth
REGULATION OR CONTROL OF SYNTHESIS OF 1,25 DHCC OR FEED BACK
MECHANISM
The synthesis of active vit. D3 or 1,25DHCC is said to be tightly and directly regulated
by the parathyroid hormone. Hence, an increase in the dietary Ca results in increased
levels of 25 (OH) CC viz., the inactive form. Any fall in the plasma Ca levels cause
release of PTH. This PTH activates enzyme 1- - hydroxylase which then converts vit.
D3 to active 1,25 DHCC.
Increases synthesis of CBP hence, there is an increase in Ca absorbed. During pregnancy,
hormones like placental lactogen and oestrogen also have an effect on 1- -hydroxylase
2) PARATHYROID HORMONE (PTH)
PTH is secreted by the parathyroid glands which acts located on the posterior surface of
the thyroid gland. They are 4 in number.
PTH acts mainly on 2 sites i.e. a) bone
b) kidney
It acts by a cAMP mechanism to increase Ca levels and decrease in organic phosphate
levels in the plasma.
a) Action on the bone Fast phase
Slow phase
16

i) Fast phase
Within few minutes of injection of a large dose of PTH, the plasma Ca levels is
said to increase.
Mechanism
PTH mainly acts by increasing the permeability of osteocytic membrane system to Ca so
that Ca from the bone fluid diffuses into the osteocytes and osteoblasts from where vit. D
mediated active transport transfers the Ca from within the OMS to the ECF thereby
increasing the plasma Ca levels.
Any decrease in the concentration of Ca within the bone fluid leads to dissolution of Ca
salts from the nearby bones without affecting the bone matrix (indirectly activates
osteoclastic activity or bone resorption).
ii) Slow phase
Several days of increased PTH activity is required to demonstrate the slow
phase.
PTH acts by
Activating the bone resorbing cells /
osteoclasts
Forming new osteoclasts from the
osteoprogenitor cells
Osteoclasts are multinucleated giant cells which produces resorption of bone
surfaces in contact with them. The osteoclasts send out long finger-like-projections
17

towards the bone. These finger like projections release a. PROTEOLYTIC ENZYMES
which digests the organic matrix.
b. ACIDS like citric / lactic acid which dissolves the bone minerals.
The Ca and PO4 released are poured into the ECF.
b) Action on kidney (↑↑Ca++
)
- Increases the resorption of Ca from the distal tubules (↓↓ PO4
– –
).
- Decreases the resorption of PO4 from PCT thereby causing phosphaturia and
hypophosphatameia.
- Increases the synthesis of 1--hydroxylase which is responsible for the active
form of Vit. D which increases Ca absorption.
REGULATION OF PTH SECRETION
The plasma Ca levels are said to have a direct influence on the PTH secretion.
Any fall in the Ca levels causes a release of the PTH which brings back the level
to normal. Similarly increase in plasma Ca level inhibits the secretion of PTH.
3.CALCITONIN
Is secreted by the parafollicular cells by the thyroid glands. Mainly acts to
maintain the integrity of the bone.
Actions
It mainly acts by decreasing the permeability of OMS to Ca thereby increasing the
amount of Ca deposited in the readily EXCHANGEABLE CALCIUM POOL OF BONE.
18

It prevents the formation of new osteoclasts from osteoprogenitor cells thereby
preventing bony resorption.
REGULATION OF SECRETION OF CALCITONIN
The release of calcitonin is regulated by the plasma calcium levels. A rise in the
plasma Ca level above 9mg% stimulates the release of calcitonin.
Hence, plasma Ca levels controls the direction of PTH and calcitonin.
In adults, role of calcitonin is very minor and normal Ca level is maintained
chiefly by PTH.
Calcitonin plays a major role in pregnancy. It protects the bones of the mother
from excessive loss of Ca as during pregnancy PTH and 1,25DHCC levels are
high.
EXCRETION OF CALCIUM AND PHOSPHOROUS
Ca is said to be excreted both in the faeces and in the urine. About 90% of the
total amount of Ca is excreted in the faeces.
Ca of the urine is excreted as calcium chloride (CaCl2) and (CaPO4)  10%
remaining.
The approximate daily turnover rates of Ca in an adult are as follows:
Intake 1000mg
Intestinal absorption 350mg
Secretion in GIT juice 250mg
Net absorption over secretion 100mg
19

Loss in the faeces 100mg
Excretion in the urine 100mg
BUFFER ACTION OF PHOSPHOROUS IN BLOOD
2 varieties of phosphates are present in the blood
Alkaline Acidic
H2PO4 HPO4
Concentration is about Concentration is about
1.05m mol/lit 0.26 m mol/lit
In the plasma they are in a ratio of alkaline 4 : 1 acidic.
Where pH of extra-cellular fluid becomes more acidic there is a relative increase in
H2PO4
–
and HPO4
– –
and the opposite happen when fluid is alkaline. The average total
quantity of inorganic phosphorous ranges between normal limits of 3-4mg/dl in adults
and 4-5mg/dl in children.
IMPAIREMENTS IN BLOOD CALCIUM
I] Hypercalcemia
Increased level of Ca in the blood.
Symptoms
- Tiredeness
- Loss of appetite.
- Nausea, vomitting.
- Constipation.
- Polyuria.
- Dehydration.
20

- Loss of muscle tone.
- Decreased excitability of muscles and nerves.
Conditions in which it occurs
- Hyperparathyroidism.
- Acute osteoporosis.
- Vit. D intoxication.
- Thyrotoxicosis.
II] Pathologic calcifications of soft tissues
3 theories have been forwarded for the mechanism of calcification
a) Nucleation theory
Ca is deposited both inside and outside the cells (in mitochondria) which later
coalesce together to form calcified tissues.
This proposes that organic matrix components facilitate precipitation by acting as
heterogenous nucleating agents like collagen, phospholipids which act on specific
phosphorylating sites.
b) Booster theory
This theory proposes the existence of a mechanism to boost the local Ca and PO4
ion product to a point where precipitation occurs.
c) Matrix vesicles
Small round vesicular extracellular matrix vesicles about 100nm in diameter are
involved in the initiation of calcification. They are probably arrived from cell
processes originating from the plasma membrane.
21

i) Dystrophic calcification
- Precipitation of Ca in degenerating and dead tissues occur.
- Common sites are - Blood vessels
- Kidneys
ii) Metastatic calcification
- Due to excess Ca in the circulating blood, they are deposited in previously
undamaged tissue
- Usually occurs in – Hyper vitaminosis D
Hyperparathyroidism
Destructive lesions of the bones.
- Common sites are - Blood vessels
- Kidney
iii) Calcinosis
- Is calcification occurring in / under skin and can be associated with scleroderma.
III] Hypocalcemia
- Decreased levels of Ca in the blood (below 4mg is lethal).
Symptoms
- Tetany (Carpopedal spasm).
a) Chvotek’s sign
- Contraction of ipsilateral facial muscles elicited by tapping over the facial nerve at
the angle of the jaw.
22

b) Trosseau sign
- Spasms of the muscles of the upper extremity that causes flexion of wrists and
thumb and extension of fingers.
- This is elicited by occluding the circulation of fingers for a few minutes.
c) Erbs sign
- Is hyperexcitability of muscles to electrical stimulation.
- This occurs in cases of – - Insufficient Ca in the diet.
- Hypoparathyroidism.
- Insufficient vit. D in the diet.
- Increase in calcitonin levels.
IV. VIT D. DEFICIENCY
 ↓↓ Ca++
level
Rickets Osteomalacia
- In children.
- Mainly affected the long bones in
the body, ribs.
- Occurs due to failure in
mineralization, due to lack of Ca level,
the cartilaginous form of bone is said to
persist.
- In adults.
- Mainly affects the flat bones in the
body.
- Especially seen in post and
menopausal women who have a
decreased dietary Ca intake and
decreased exposure to the sun resulting
in increased removal of Ca from the
bone causing softening of the skeleton
and its distortion.
- The cartilage continuous to grow -
23

and proliferate thus resulting in
localized areas of cartilage proliferation
(rickety rosary, beaded bone formation)
- The weight of the body on the
uncalcified long bones result in the
bowing of legs – knock kness.
Dental
- Development of abnormality in
enamel and dentin.
- Delayed eruption of teeth.
- Mal-alignment of teeth.
- Higher caries index.
- Wider predentine zone.
- Increased amount of inter-globular
dentin.
Dental Findings
- Severe periodontitis
Treatment: Treatment:
Supply adequate amount of Ca and
phosphate in diet and administration of
large amounts of Vit. D.
V. PARATHYROID HORMONE
24

a) Hyperparathyroidism
- Increases levels of PTH due to an adenoma of the parathyroid glands.
C/F:
- Pathologic fracture of bones due to increased mobilization of Ca from bone
resulting in osteitis fibrosa cystica.
- Large punched out cystic area of bone.
o Joint stiffness.
o Urinary tract stones.
o Muscle weakness.
o Thirst.
o Polyuria
o Anorexia.
o Weight loss.
Dental findings
- Malocclusion seen due to definite drifting of teeth causing spacing (this occurs as
a result of increased loss of Ca from the bone, there is an absolute attempt to new
bone formation and repair resulting in spacing).
Radiographically
- Areas of radiolucency seen in bone.
- Loss of lamina dura present.
25

Treatment
- Removal of cause.
b) Hypoparathyroidism
- Seen to develop due to excision of the parathyroid glands.
- This is characterized by a fall in the serum Ca levels and an increase in the serum
inorganic phosphate levels.
C/F:
- Similar to hypocalcemia.
- Tingling and numbness in the fingers, face and toes.
- Extreme cases – cramps in the hands and feel which is very painful.
- Carpopedal spasm.
- Spasm of muscles of respiration resulting in the dread of suffocation.
- Signs of tetany present.
- In infants, symptoms of tetany may be confused for epilepsy, though there is no
loss of consciousness.
Dental Findings
- Aplasia / hypoplasia of teeth seen when hypoparathyroidism develops before teeth
formation.
c) Parathyroid poisoning
26

- In rare cases, the PO4 level of body fluids rise rapidly when the kidneys cannot
excrete rapidly. Ca and PO4 get supersaturated and lead to metastatic deposition in
lungs, alveoli, kidneys, thyroid gland, gastric mucosa etc.
- Elevation of blood Ca levels before 17 mg/dl along with concurrent elevation of
PO4
– –
death can occur in few days.
Osteoporosis
- In adults (old age) due to decreased bone matrix rather than poor bone
calcification.
Summary
Ca and PO4 are important minerals that are required in minimal amounts for basic
activities in the body like the normal ionic Ca levels in the plasma is required for proper
bone mineralization and maintenance of cell membrane integrity. The plasma Ca levels
need to be regulated within a very narrow range because of its marked effect on
neuromuscular and cardiac excitability.
Three hormones which are – PTH
- Calcitonin
- Vit. D
Play important role in maintaining Ca and PO4 levels to a normal.
27

References and Suggested Reading
1. The Physiology and Biochemistry of Mouth – Jenkins
2. Applied Physiology – Sampson Wright
3. Textbook of Medical Physiology – Sheerwood
4. Review of Medical Physiology – Ganong
5. Physiology- Bern & Levy
6. Textbook of Medical Physiology- Guyton Hall
7. Textbook of Internal Medicine – Harrisson
8. Textbook of Medicine – Davidson
28

Calcium and Phosphate Metabolism Guide

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Calcium and Phosphate Metabolism Guide