2. Calcium Homeostasis

3. First, Let’s Take a Look at This
Diagram…… Homeostasis of Calcium

4. Where Do I Get My Calcium?
% 70 inorganic matrix composed of
Calcium Salts in Hydroxyapatite
Ca10(PO4)6(OH)2.
The skeleton is resevoir for the
minerals Calcium (and
phosphorous).
Resorption: the process of
dissolving bone and releasing its
minerals into the blood for other
uses. The OSTEOCLAST
secretes ACID PHOSPHATASE
or sometimes HCL to digest
bone matrix. Secreted by
lysosomes.

5. Resorption and Remodeling
Resorption
Osteoclasts do this
using HCL and ACID
PHOSPHATASE to
dissove bone matrix
Remodeling
Ostoblasts do this
Collagen fibers and
hydroxyapatite matrix

6. Its Role in Calcium
Homeostasis
VITAMIN D
TThe vitamin That Works
Like a hormone

7. How Does “D” Compare To
Hormones?
Vitamin D3 is not secreted by a classical endocrine
gland, the active form of the hormone is released
from the kidney and acts at distant sites or locally.
Each of the forms of vitamin D is hydrophobic, and is
transported in blood bound to carrier proteins.
Only a very remains in a free form in the circulation and
has a serum t1/2 of about 5 hours small proportion of
vitamin D

9. To Make Me D, Warm Me Up and
Hydroxylate Me..3X!

10. So..Exposure to Sun and Then, Fortified
Foods….Give Us the D We Need

11. How Does Vitamin D Facilitate Calcium
Absorption in the Intestines??

12. IN THE INTESTINE
It facilitates intestinal absorption of calcium,
as well as stimulates absorption of phosphate
and magnesium ions.
In the absence of vitamin D, dietary calcium is
not absorbed at all efficiently.
Vitamin D stimulates the expression of a
number of proteins involved in
transporting calcium from the lumen of the
intestine, across the epithelial cells and
into blood.

13. The vitamin D form, 1,25-
dihydroxcholecalciferol [1,25(OH)2D3],
1. stimulates the synthesis of the epithelial calcium
channels in the plasma membrane calcium pumps , and
2. induces the formation of the calbindins.

14. Vitamin D: Its Role is ABSORPTION of CALCIUM ,and
to a lesser extent, Phosphorous, from the Small
Intestine and Duodenum.

15. Once joined with ingested vitamin D,
facilitate increased serum calcium
levels .
Shows Expressed Calbindins and
How the facilitate transport of Calcium

16. Calcium Absorption Enhanced by Carrier
Protein Calbindin


17. Calcium absorption is transport across the
epithelial cell, which is greatly enhanced
by the carrier protein calbindin, the
synthesis of which is totally dependent on
vitamin D

18. Calcitriol Raises Blood
Calcium in 3 Ways:
1. Increases Ca++
absorption by the small
intestine.
2. Increases Calcium
(and Phosphate )
resorption from the
skeleton. It binds to
hematopoietic stem
cells and causes
differentiation of
osteoclasts.
3. Weakly promotes the
reabsorption of
Calcium ions by the
kidney cells (less
calcium excreted)

19. Let’s Look A Bit Closer at RANK L

20. But, I thought Vitamin D HELPED US
retain Calcium?
 Yes, It does. So, although there is some
proliferation of osteoclasts the
 NET RESULT IS:
CALCIUM ABSORPTION and
REMODELING….Outweighs
RESORPTION…. Because…

21. Vitamin D has also been shown to play an
important part in regulating the
proliferation and differentiation
of both types of bone
remodeling cells - those
responsible for bone
breakdown and those that
reform the bone anew…and
more.

22. Consider Calcium Itself

23. Got Milk?
Ages 19 -50 : need 1000 mg/ day in diet
Major Food Sources Include:
Dairy products Others: dark leafy greens
Sardines w/ bones
Fortified cereals
Most Tofu

24. Calcium Is Needed For:
Bone Matrix (70%
Ca0H in form of
Hydroxyapatite)
Muscle Contraction
Nerve Impulses
Blood Clotting
Cellular
Metabolism

25. Calcium Homeostasis
We need to maintain a calcium
blood level of 9-11 mg/ 100ml

26. What HOMEOSTASIS IS NOT
MAINTAINED? WHAT ARE THE
IMMEDIATE DANGERS?
Blood Calcium TOO LOW…We call this
TETANY: Inability for muscles to relax
( muscles tremer i.e carpopedal spasms
and larngospasms….shuts off air… and
can cause suffocation..
BLOOD CALCIUM TOO HIGH…..Its called
Hypercalcemia…sluggush nervous system.
And possible cardiac arrest.

27. Parathyroid Gland Anatomy
Four Parathyroid
glands are usually
found posterior to
the thyroid gland
Total weight of
parathyroid tissue is
about 150mg
Parathyroid hormone
(PTH) is made by
these glands

28. Low Blood Calcium
• Parathyroid gland releases parathyroid hormone
• Stimulates osteoclasts to resorb Ca++
• Blood calcium rises
• Promotes the final step of Calcitriol synthesis by
kidneys
Feedback Inhibition
High Blood Calcium
• Inhibits parathyroid gland

29. Calcitonin
Calcitonin is a peptide
hormone secreted by the
parafollicular or “C” cells of
the thyroid gland
It is synthesized as the
preprohormone & released in
response to high plasma
calcium
Calcitonin acts on bone
osteoclasts to reduce bone
resorption.
Net result of its action is a
decline in plasma calcium &
phosphate

30. Control of Calcium Homeostasis
The Role Calcitriol plays in
maintaining normal blood
calcium concentration.

31. Correction for
Hypocalcemia

32. Correction for
Hypercalcemia

33. Osteoblasts- cells that form
bone during both
ossification and
remodeling
Osteoclasts- Cells
responsible for bone
resorption.(FROM Blood)
Vitamin D- plays a key role
in regulating the
proliferation and
differentiation of both of
these cells

34. Reversing Things A Bit:
Can I Deplete My Calcium Storage
By Lifestyle?
IF SO…….HOW???

35. 35
Nutrition and OP
Aside from getting enough calcium and
Vitamin D, the single most important point
is . . .
Avoid dietary approaches that deplete
calcium!!
OP : stands for Osteoporosis

36. 36
Preventable Risks
Sedentary lifestyle (REMEMBER WOLF”S
LAW)
Insufficient calcium or vitamin D intake
Diet high in meat-based protein
Excessive caffeinated beverages if low calcium
intake
Cola drinks
Alcohol consumption,

37. REMEMBER
Stress causes …bone building
Lacking of use…..bone resorption
LET’s add to this…acididosis-like
condition in the blood…. ..BONE
RESORPTION!!!
Here’s where the excess protein, cola and
caffeine will come into play.

38. How Does Eating Too Much Meat
Cause Our Bones To Thin?

39. 39
How Does This Calcium Depletion
Occur?
When you take in more protein than you need,
your body cannot store extra protein
(animal protein is more dense than plant protein
so we get more protein than we need
It converts amino acids into organic acids that
acidify the bloodstream.
The kidneys neutralize the acidity by pushing
large amounts of calcium into the blood and then
out via urine.

40. COLA DRINKS…..BAD FOR
BONES
IN SEVERAL STUDIES IT HAS BEEN
SHOWN THAT:
Intake of cola, but not of other carbonated
softdrinks, is associated with low (BONE
MINERAL DENSITY) BMD in women.
Data is collected from Femoral Neck

41. What are the consequences of
INEFFICIENT CALCIUM early in life?

42. Rickets
The specific radiographic
features of rickets reflect
the failure of cartilage
calcification and
endochondral ossification
and therefore are best
seen in the metaphysis of
rapidly growing bones ).
The metaphyses are
widened, uneven,
concave, or cupped and
because of the delay in or
absence of calcification,
the metaphyses could
become partially or totally
invisible.

43. Later in Life….Osteoporosis and
Osteomalacia
Osteoporosis is the loss of bone density
Osteomalacia is lack of mineralization