This document discusses calcium metabolism in the human body. It states that calcium is the most abundant mineral in the body, found mainly in bones and teeth where it provides structural support. It also discusses calcium homeostasis, which is maintained by two homeostatic systems - one that regulates plasma calcium levels and another concerned with bone remodeling. Key factors involved in calcium homeostasis include parathyroid hormone (PTH), vitamin D, and calcitonin. The document outlines where calcium is stored, absorbed and excreted in the body and factors that influence these processes like dietary intake, kidney function, and bone turnover.

1. Ca
METABOLISM
by
Dr. Suman Kumar
DNB-orthopaedics
DDU hospital

2. GENERAL CONSIDERATION
 Ca, THE MOST ABUNDANT BODY-MINERAL
 PRESENT MAINLY IN BONES & TEETH GIVING
STRUCTURAL SUPPORT
 ALSO PRESENT IN ECF & INSIDE DIFFERENT
CELLS, NEEDED FOR MUSCLE
CONTRACTION, HORMONES & ENZYMES
SECRETION, HELPING NEURONS IN SENDING
MESSAGES, BLOOD-COAGULATION etc.
 CONSTANT NORMAL LEVEL FOR PROPER FUNCTION

3. HUMAN BODY COMPOSITON
IN ADULT HUMAN BODY 1-2 kg Ca
AVERAGE ADULT MAN-1300gm & WOMEN-
1000gm
≥ 99% IN SEKELETON AS HYDROXYAPATITE
[Ca10(PO4)6(OH)2] PROVIDING MECHANICAL
STABILITY
1% IN ECF & OTHER CELLS FOR DIFFERENT
FUNCTIONS

4. Ca IN BONE
BONES THE IMPORTANT STORAGE POINT FOR
CALCIUM
SKELETAL CALCIUM ACCRETION 1ST SIGNIFICANT
DURING 3RD TRIMESTER OF FETUS
ACCELERATES THROUGH CHILDHOOD &
ADOLESCENCE
PEAK IN EARLY ADULTHOOD ~30YR WHN PEAK BONE
MASS REACHED
PEAK BONE MASS- MAX AMOUNT OF BONE
ACHIEVED
DECLINES THEREAFTER @ ≤1-2%PER YR

5. Ca IN BONE
 Ca IN BONE AS HYDROXYAPATITE
[Ca10(PO4)6(OH)2] IN THE FORM OF CRYSTAL
LATTICE
 Na+, K+, Mg2+, & F-, ALSO ARE PRESENT IN THE
CRYSTAL LATTICE

6. Ca IN BONE
TWO TYPES OF Ca POOL IN BONE :-
1)READILY EXCHANGEABLE POOL-SMALLER
RESORVOIR (0.5-1% OF BONE Ca)
2)SLOWLY EXCHANGEABLE POOL-STABLE
TWO INDEPENDENT HOMEOSTSTIC SYSTEM:-
1ST SYSTEM REGULTES PLASMA CALCIUM
2NDCONCERNED WITH BONE REMODELING
TWO SYSTEM INTERACTING WITH EACH OTHER

7. 1ST HOMEOSTATIC SYSTEM
• IT REGULATES PLASMA CALCIUM
• 500mmol/d Ca MOVES IN & OUT OF READILY
EXCHANGEABLE POOL INTO PLASMA
• READILY EXCHANGEABLE POOL IN CHEMICAL
EQUILIBRIUM WITH ECF

8. 2ND HOMEOSTATIC SYSTEM
CONCERNED WITH BONE REMODELLING
CONSTANT INTERPLAY OF BONE RESORPTION
& DEPOSITION
MEDIATED BY COUPLED OSTEOBLASTIC &
OSTEOCLASTIC ACTIVITY
95% OF BONE FORMATION IN ADULT
Ca EXCHANGE BETWEEN PLASMA & STABLE
POOL @7.5mmol/d(250-500mg/d)

9. Ca IN ECF
TOTAL 1-2 gm Ca IN ECF
NORMAL [s.Ca ]=8.5-10.4mg/dL(2.1-
2.6mmol/L) IN ADULT
3 DISTINCT FORM OF Ca IN ECF-
a.IONIZED
b.COMPLEXED
c.PROTEIN BOUND

10. Ca IN ECF
PLASMA Ca:2 FORMS-
1.DIFFUSIBLE(60%)-CAN CROSS CELL-
MEMB; 2 TYPES-
a)IONIZED: Ca²⁺(50% OF TOTAL ECF Ca)
b)COMPLEXED TO
HCO3¯,CITRATE,PHOSPHATE etc.(10%)
2.NON-DIFFUSIBLE(40%)-PROTEIN
BOUND

11. Ca IN ECF
• ONLY IONIZED Ca²⁺ EXERTS BIOLOGICAL
EFFECTS
• DEGREE OF COMPLEX FORMATION DEPENDS
ON AMBIENT pH, *Ca²⁺+ & *COMPLEXING
IONS]
• AT HIGH pH, MORE ANIONS BIND TO Ca²⁺
→LOW *Ca²⁺+

12. Ca IN ECF
PRTEIN BOUND Ca- 90% BOUND TO
ALBUMIN-READILY REVERSIBLE
-10% WITH GREATER AFFINITY TO β-
GLOBULIN, α₂-GLOBULIN, α₁-GLOBULIN & γ-
GLOBULIN
-CHANGES IN pH→CHANGES IN [PROTEIN
BOUND Ca]
- ↑pH →↑PROTEIN-ANION & BINDS TO Ca²⁺
→↓*Ca²⁺+

13. Ca & PLASMA PROTEIN
 TOTAL [PLASMA Ca] CHANGES WITH CHANGE
IN [PLASMA PROTEIN]
 A CHANGE IN 1 gm/dL OF *ALBUMIN+→
CHANGE IN 0.8 mg/dL OF TOTAL Ca
 EACH 1 gm/dL ↓IN ALBUMIN →↑0.8mg/dL
OF TOTAL Ca
 1g/L ↓ IN ALBUMIN →↑0.02mmol/L OF s.Ca

14. CORRECTED Ca-LEVEL
• CORRECTED Ca-LEVEL(mg/dL)= measured
total Ca(mg/dL) + 0.8[4.0-s.Albumin
level(gm/dL)] where 4.0 is the average
s.Albumin level
• CORRECTED Ca-LEVEL(mmol/L)= )= measured
total Ca(mmol/L)+0.02[40-s.Albumin level(in
gm/L)]

15. DIETARY INTAKE OF Ca
• SOURCES-MILK & DAIRY
PRODUCTS, FISHES, LEAFY GREEN VEGETABLES
etc.
• Ca OF LEAFY GREEN VEGETABLES POORLY
ABSORBED-PRESENCE OF PHYTATES WHICH
COMPLEX WITH Ca

17. Male and Female Age Calcium (mg/day) Pregnancy & Lactation
0 to 6 months 210 N/A
7 to 12 months 270 N/A
1 to 3 years 500 N/A
5 to 8 years 800 N/A
9 to 13 years 1300 N/A
14 to 18 years 1300 1300
19 to 50 years 1000 1000
51+ years 1200 N/A

18. Ca-ABSORPTION IN INTESTINE
TWO TYPES :
ACTIVE-TRANSCELLULAR
PASSIVE-PARACELLULAR
 PASSIVE DIFFUSION-FACILITATED
-5% OF DAILY INTAKE
-COUNTERBALANCED BY DAILY
INTESTINAL Ca LOSS(MUCOSAL & BILLIARY
SECRETION,SLOUGHED CELLS) ~150mg/d

19. Ca-ABSORPTION IN INTESTINE
ACTIVE- IN DUODENUM & PROXIMAL
JEJUNUM
-1,25-(OH)₂D DEPENDENT
-20-70% OF DAILY INTAKE
3 STEPS- Ca ENTRY ACROSS MUCOSAL CELL
-DIFFUSION THROUGH CELL
-ACTIVE EXTRUSION ACROSS SEROSAL
MEMBRANE(ENERGY DEPENDENT)

21. Ca-ABSORPTION IN INTESTINE
• CALCITRIOL i.e. 1,25-(OH)₂D ENHANCES ALL 3
STEPS
• TRPV6 (transient recptor potential channel)IN
PROXIMAL BOWEL MEDIATES MUCOSAL
ENTRY OF Ca
• TRPV6 IS VIT-D DEPENDENT
• CALBINDIN-D9K ENHANCES EXTRUSION OF Ca
BY Ca-ATPase
• 1,25-(OH)₂D UPREGULATES BOTH CALBINDIN-
D9K & Ca-ATPase

23. Ca-ABSORPTION IN INTESTINE
LOW Ca-INTAKE→↑ed FRACTIONAL
ABSORPTION OF Ca DUE TO ACTIVATION OF
VIT-D
HIGH Ca INTAKE→ACTIVE TRANSPORT
MECHANISM SATURATED &1,25(OH)₂-D ↓ →
DECREASED Ca ABSORPTION

24. ROLE OF KIDNEY IN Ca
METABOLISM
 8-10 gm/d Ca FILTERED
 ≥98% REABSORBED-65%IN PCT & REST IN
cTAL & DT
 cTAL CELLS HAVE PARACELLIN-1
RESPONSIBLE FOR Ca ABSORPTION
 ↑ed s.Ca LEVEL INHIBITS PARACELLIN-1 &
Ca-ABSORPTION IN cTAL
 10% Ca ABSORBED IN DT BY
TRANSCELLULAR PROCESS

26. ROLE OF KIDNEY IN Ca
METABOLISM
 IN DCT Ca MOVES ACROSS CELL WITH HELP OF
CALBINDIN-D28K, Ca²⁺-ATPase
&Na⁺/Ca⁺EXCHANGERS
 ALL OF THESE PROCESS ↓CONTROL OF PTH
 KIDNEY IS ALSO THE SITE OF ACTIVATION OF
VIT-D ↓ INFLUENCE OF PTH

27. Ca HOMEOSTASIS

28. Ca HOMEOSTASIS
ECF Ca IS CONTROLLED BY CLASSICAL –VE
FEEDBACK SYSTEM
PTH ACTS ON BONE,KIDNEY & ON VIT-D
VIT-D ACTS ON BONE & INTESTINE
CALCITONIN ACTS OPPOSITE OF PTH
s. Ca LEVEL CONTROLS LEVEL OF
PTH,CALCITONIN

29. Ca HOMEOSTASIS
↓BONE RESORPTION SUPPRESS PTH
↑URINARY LOSS
↓1,25(OH)₂ D PRODUCTION
RISING BLOOD Ca²⁺
NORMAL BLOOD
Ca²⁺
FALLING BLOOD
Ca²⁺
↑ BONE RESORPTION
↓ URINARY LOSS STIMULATE PTH
↑ 1,25(OH)₂ D PRODUCTION

30. Ca HOMEOSTASIS

31. Ca HOMEOSTASIS
PTH & VIT-D ACTS ON OSTEOCLASTS -
MOBILIZES Ca TO PLASMA
VIT-D ACTS ON INTESTINAL CELLS –
INCREASES ABSORPTION OF Ca
PTH ACTS ON KIDNEY- MORE Ca
REABSORBED, ALSO MORE 1,25(OH)₂-D
FORMED→ MORE Ca ABSORBED IN INTESTINE

34. DISORDER OF Ca METABOLISM
• RICKETS
• OTEOMALACIA
• OSTEOPOROSIS
• HYPOCALCEMIA
• HYPERCALCEMIA

35. THANK YOU