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DR. LAXMIKANTA DR. LAXMIKANTA SAYSAY
Metabolism of Calcium, Phosphate & Vit. D
Parathyroid gland
&Calcitonin
CALCIUM CALCIUM METABOLISMMETABOLISM
Distribution of Ca in Distribution of Ca in ECFECF
FUNCTIONS OF CALCIUMFUNCTIONS OF CALCIUM1. Calcium Homeostasis2. Promotes Neuromuscular
excitation-contraction coupling3. Blood Coagulation4. Membrane integrity & stabilization
of cell Membrane5. Release of Neurotransmitters from
synaptic vesicles6. Secretion from endocrine gland7. Synthesis of Nucleic acids &
proteins8. Activation of enzymes
Adult Man 800 mg/dayWomen, pregnant, lactation & post-menopause
1500 mg/day
Children (1-18Yrs) 800-1200 mg/day
Infants ( < 1Yr) 300-500 mg/day
Dietary requirements
Dietary SourcesMilk & Milk products
Beans, Leafy vegetables, Fish, Cabbage, Egg Yolk
CALCIUM BALANCECALCIUM BALANCE
PHOSPHOROUS PHOSPHOROUS METABOLISMMETABOLISM
FUNCTIONSFUNCTIONS1. Development of bone & teeth2. Structural Part of : i. High energy transfer - ATP, GTP ii. Co-factors – NAD, NADP, TPP iii. Second Messenger – cAMP, inositol
triphosphate iv. Nucleic acids (DNA & RNA)
3. Activation of enzymes by phosphorylation4. Role in Carbohydrate metabolism5.Phosphate buffer sysytem –pH regulation6.Balances intracellular anions
PHOSPHOROUS BALANCEPHOSPHOROUS BALANCE
Vitamin D Vitamin D
CHOLESTEROL CHOLECALCIFEROL
A
C D
B
SYNTHESISSYNTHESIS
REGULATION OF SECRETION OF Vit. REGULATION OF SECRETION OF Vit. DD
Other sites of Calcitriol Other sites of Calcitriol synthesissynthesis
Placenta Keratinocytes Macrophages
Mechanism of ActionMechanism of Action
ACTIONS OF Vit. DACTIONS OF Vit. D
Intestinal Ca absorptionIntestinal phosphate absorption
Renal excretion of Ca and phosphate
Action on bone
Applied AspectApplied Aspect
Rickets and OsteomalaciaVit. D resistance ricketsOsteoporosis
RicketsRicketsClinical FeaturesA. Bone defect1. Craniotabes2. Widening of wrist3. Collapse of Chest Wall4. Rickety Rosary5. Frontal bossing & posterior flattening
of skull6. Harrison’s Sulcus7. Bowing of Legs or Knock-knee8. Kyphosis & Pelvic deformities
B. General Features 1. Respiratory & G.I. infections 2. Developmental milestone Delay
C. Tetany & ConvulsionsD. Biochemical Changes Low plasma Calcium & PhosphateSerum alkaline phosphatase levels HighPlasma Calcitriol low & absentMangementVit. D 25-125 µgm (1000-5000 IU)/day 6-
8 wks
OsteomalaciaOsteomalaciaAmount of mineral accretion in bone per Amount of mineral accretion in bone per
unit of bone matrix is deficientunit of bone matrix is deficientFemalesFemales - Multiple pregnancies,
Lactation, Some time in Puberty
Clinical ManifestationClinical Manifestation i. Long bone - soft, painful, deformed &
terdernessii. Fractures occurs easilyiii. Proximal Myopathyiv. S.Ca2+ low, S. inorganic phosphate low,
S.alkaline phosphatase high
OsteoporosisOsteoporosis
Decrease in all constituents of Bone
Decrease in bone mass with preservation of normal ratio of mineral to matrix
Age >40yrs
Postmenopausal women
Parathyroid Parathyroid HormoneHormone
ANATOMYANATOMY
SYNTHESISSYNTHESIS
MECHANISM OF ACTION MECHANISM OF ACTION
Feedback MechanismFeedback Mechanism
ACTIONSACTIONS1. Effect on calcium & phosphate concentration in ECF
2. Absorption of calcium and phosphate from bone
3. Excretion of calcium and phosphate by kidney
4. Intestinal absorption of calcium and phosphate
5. Action on other ions
Applied Applied
HypoparathyroidismHyperparathyroidismPseudohypoparathyroidism
Hypoparathyroidism Hypoparathyroidism
Cause – ThyroidectomyChvostek′ s sign Trousseau′s sign
HYPERPARATHYROIDISMHYPERPARATHYROIDISM
PTHrPPTHrP140 aminoacidsEncoded by chromosome -12Site of synthesis – uterus , enamel ,
brain , Keratinocytes , smooth muscle
Action1.Growth and development of
cartilage in utero2.Transport of Ca in placenta3.Skeletal development4.Inhibit excitatory damage to
developing neuron
CALCITONINCALCITONINPolypeptide with 32 aminoacidSecreted from Clear cells (C – Cells) Clear cells (C – Cells)
or parafollicular cells of Thyroid gland
Also known as ThyrocalcitoninThyrocalcitonin
Normal Secretion is 0.5 mg/dayHalf Life 15 min.MW – 3000Normal Plasma Level – 0.2 ngm/ml
SECRETIONSECRETION
Stimulators1.Plasma Ca2.β- adrenergic agonist3.Dopamine4.Estrogen5.Gastrin6.CCK – PZ7.Glucagon8.Secretin
ACTIONACTIONBoneBone i. Inhibit osteoclastic activity ii. Inhibit active transport of Ca from bone to
ECFiii. Increase alkaline phosphatase synthesis
from osteoblast
KidneyKidney i. Synthesis of 1,25 DHCCii. Na+, Ca2+, Cl -, PO4 excretioniii. Excretion of Hydroxyproline derived from
bone
Cont.Cont.GITGIT i. Secretion of Water & Electrolyte ii. Gastric Motility & Acid secretionIii. Jejunal absorption of Ca2+ &Phosphate
Physiological significancePhysiological significance i. Active in Young individuals ii. Promote Ca2+ storageiii. Protection against Post prandial
hypercalcemiaiv. Protection of Mother during pregnancy
Calcium HomeostasisCalcium Homeostasis↓ Plasma Ca
↑ PTH secretion from parathyroid gland
↑ Plasma PTH
KIDNEY↑ Ca reabsorption ↑ 1,25 DHCC
Bone↑ Resorption
↓ Urinary excretion of Ca
↑ plasma 1, 25 DHCC
↑ Release of Ca into plasma
↑ Ca absorption in intestine
Restoration of plasma Ca towards normal
THANK YOUTHANK YOU