This document summarizes calcium homeostasis and the roles of parathyroid hormone (PTH) and vitamin D in regulating calcium levels. PTH and vitamin D work to maintain calcium levels in the blood by increasing calcium absorption in the intestines and kidneys. PTH acts directly on bones to increase calcium levels by promoting bone resorption, while vitamin D works indirectly by stimulating the kidneys to produce calcitriol, which then increases calcium absorption in the intestines. Together, PTH and vitamin D are the key hormones that regulate calcium homeostasis.
9. Hormones and Calcium Homeostasis
▪ “Parathyroid hormone (PTH) and vitamin D are
the two hormones that play the dominant role
in the regulation of calcium homeostasis”
10
12. Parathyroid Hormone
▪ Has 84 amino acids – Secreted by Parathyroid glands
▪ The first 35 amino acids of PTH are biologically active
▪ Control of release of the hormone is by negative feedback by the
ionized calcium in serum
▪ The release of hormone is mediated by cyclic AMP
▪ The normal PTH level in serum is 10–60 ng/L
▪ Mechanism of Action of Parathyroid Hormone
▪ PTH activates adenylyl cyclase with consequent increase in
intracellular calcium concentration.
13
13. Actions of PTH
1) PTH and bones
▪ In the bone, PTH causes demineralization.
▪ The numbers of osteoclasts are also increased.
▪ Osteoclasts release lactate which solubilizes calcium.
2) PTH and kidney
▪ In kidney, PTH causes decreased renal excretion of calcium and
increased excretion of phosphates.
3) PTH and intestines:
PTH stimulates 1-hydroxylation of 25-hydroxycalciferol in kidney to
produce calcitriol. This indirectly increases calcium absorption.
14
15. VITAMIN D
Metabolic product of the cholesterol synthetic
pathway.
The tissues that are involved in the synthesis of
vitamin D are the skin, liver, and kidneys and the
tissues it affects are the gut, bone, and
parathyroids
16
18. ▪ Actions:
1)increase Ca absorption from intestine.
2) increase PO4 absorption from intestine.
3) increase renal reabsorption of Ca &PO4.
4) increase bone resorption from old bone &mineralize
new bone {net resorption} .
Overall effect : ↑ serum Ca & PO4 .
Vitamin D
19. Calcitonin
▪ A Polypeptide - secreted by the thyroid parafollicular or clear cells.
▪ Decreases serum calcium level.
▪ Inhibits resorption of bone (decreases the activity of osteoclasts
and increases that of osteoblasts)
▪ Calcitonin and PTH are directly antagonistic.
▪ PTH and Calcitonin together promote the bone growth and
remodeling.
▪ Kidneys – increase excretion of calcium and phosphorus.
22
20. 23
Comparison of action of three major factors affecting serum calcium
Vitamin D PTH Calcitonin
Blood calcium Increased Drastically
increased
Decreased
Main action Absorption
from gut
Demineralisation Opposes
Demineralisation
Calcium absorption from gut Increased Increased (indirect)
Bone resorption decreased Increased decreased
Deficiency manifestation Rickets Tetany --
Use in rickets drug of choice contraindicated theoretically
beneficial
Effect of excess Hypercalcemia
+
Hypercalcemia++ Hypocalcemia
22. Calcium in cells
Calcium is mainly extra-cellular, but also present in
intracellular compartment
Entry into cells:
▪ Calcium influx by Na/Ca exchange mechanism
▪ Entry of calcium into mitochondria by a calcium uniport
system
23. Exit out of cells
▪ By Na-Ca antiport system, which in turn is
dependent on the Na-H-ATPase pump, this is
called calcium pump
Other calcium channel
▪ Voltage operated channel, second messenger
operated channel
29. 32
Upon getting the Neural signal
Calcium released from sarcoplasmic reticulum
Calcium activates ATPase
Increases action of actin and myosin
Excitation –contraction coupling.
30. 33
▪ Trigger by interaction of calcium with Troponin C
▪ The Active Transport System utilizing calcium
binding protein is called calsequestrin
▪ Ca decreases neuromuscular irritability
▪ Deficiency-Tetany
33. SECOND MESSENGER
Calcium and cyclic AMP are second messenger of
different hormone
eg: Glucagon
Calcium is used as second messenger in systems
involving G proteins and Inositol triphophate.
36
35. COAGULATION:
• Factor IV (ca) – Blood coagulation cascade
• Prothrombin contain gamma carboxy glutamate
residues – Chelated by calcium during thrombin
formation
36. Myocardium
Calcium prolongs SYSTOLE
In hypercalcemia, cardiac arrest is seen in systole
This fact should be kept in mind before giving it
Intravenously (Should be given very slowly)
39
37. Bone and teeth
The bulk quantity of calcium is used for bone and
teeth formation
Bone also act as reservoir for calcium the body
Osteoblast- bone deposition
Osteoclast-demineralization
40
38. Calcium in blood
▪ Normal blood level:9 – 11mg/dl
▪ Ionized calcium :5mg/dl metabolically active.
▫ 1mg/dl complexed with
phosphate,bicarbonate,citrate.
▪ Protein bound calcium: 4mg/dl protein bound. Non
diffusible.
41
43. “ Painful Bones, Renal Stones, Abdominal Groans,
Psychic Moans and Neuro-Psychiatric over-tones”
46
Clinical Features
44. Management of hypercalcemia
‰
▪ Adequate hydration,
Furosemide IV to promote calcium excretion
Steroids, if there is calcitriol excess
Definitive treatment for the underlying disorder
47
45. Causes of Hypocalcemia
1. Deficiency of vitamin D
▪ Decreased exposure to sunlight
▪ Malabsorption, dietary deficiency
▪ Hepatic diseases
▪ Decreased renal synthesis of calcitriol
▪ Nephrotic syndrome (binding protein lost)
▪ Anticonvulsant therapy
2. Deficiency of parathyroid
▪ Hypoparathyroidism (primary, secondary)
3. Increased calcitonin
▪ Medullary carcinoma of thyroid
49
48. Treatment of Hypocalcemia
52
1. Oral calcium, with vitamin D supplementation
2. Underlying cause should be treated
3. Tetany needs IV calcium (usually 10 mL 10% calcium
gluconate over 10 minutes, followed by slow IV infusion).
IV calcium should be given only very slowly
57. Function
1. Formation of bone and teeth
2. Production of high energy phosphate
compounds such as ATP, CTP, GTP
3. Synthesis of nucleoside coenzymes such
as NAD and NADP
4. DNA and RNA synthesis, (phosphodiester
linkages)
64
58. 65
4. Formation of phosphate esters, such as glucose-
6-phosphate
5. Formation of phospho proteins, e.g. Casein
6. Activation of enzymes by phosphorylation
8. Phosphate buffer system in blood. The ratio of
Na2HPO4: NaH2PO4 in blood is 4:1 at pH of 7.4
60. 67
Factor favouring absorption Factor inhibiting absorption
Bile salts
Acidity
Calcium absorption of phosphorus is
optimum when dietary Ca : p ratio is
between 1:2 and 2:1
Cholecalciferol (active vit D) enhance
absorption
Parathyroid hormone stimulate
synthesis of active vit D (indirectly)
High calcium – phosphate ratio
phytates (form insoluble
calcium salt)
Alkalinity
Magnesium and aluminium
(form insoluble salt)
Parathyroid hormone
61. Excretion
▪ Through urine (2/3rd of ingested phosphorous) and
through stool( unabsorbed)
▪ Normally 0.6 g/d is excreted through urine
68
Factor decreasing excretion Factor increasing excretion
Cholecalciferol- increase
reabsorption of phosphorous
by renal tubule
Low plasma phosphorous level
Parathyroid hormone-
decrease renal
reabsorption
69. IN TWO OR THREE COLUMNS
Yellow
Is the color of gold,
butter and ripe lemons.
In the spectrum of
visible light, yellow is
found between green
and orange.
Blue
Is the colour of the
clear sky and the deep
sea. It is located
between violet and
green on the optical
spectrum.
Red
Is the color of blood,
and because of this it
has historically been
associated with
sacrifice, danger and
courage.
76
70. A PICTURE IS WORTH
A THOUSAND WORDS
A complex idea can be conveyed with
just a single still image, namely making
it possible to absorb large amounts of
data quickly.
77
78. LET’S REVIEW SOME CONCEPTS
Yellow
Is the color of gold, butter and
ripe lemons. In the spectrum of
visible light, yellow is found
between green and orange.
Blue
Is the colour of the clear sky
and the deep sea. It is located
between violet and green on
the optical spectrum.
Red
Is the color of blood, and
because of this it has
historically been associated
with sacrifice, danger and
courage.
Yellow
Is the color of gold, butter and
ripe lemons. In the spectrum of
visible light, yellow is found
between green and orange.
Blue
Is the colour of the clear sky
and the deep sea. It is located
between violet and green on
the optical spectrum.
Red
Is the color of blood, and
because of this it has
historically been associated
with sacrifice, danger and
courage.
85
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3000
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1000
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92
87. TIMELINE
94
DEC
NOV
OCT
SEP
AUG
JUL
JUN
MAY
APR
MAR
FEB
JAN
Blue is the colour of
the clear sky and the
deep sea
Red is the colour of
danger and courage
Black is the color of
ebony and of outer
space
Yellow is the color of
gold, butter and ripe
lemons
White is the color of
milk and fresh snow
Blue is the colour of
the clear sky and the
deep sea
Yellow is the color of
gold, butter and ripe
lemons
White is the color of
milk and fresh snow
Blue is the colour of
the clear sky and the
deep sea
Red is the colour of
danger and courage
Black is the color of
ebony and of outer
space
Yellow is the color
of gold, butter and
ripe lemons
88. ROADMAP
95
1 3 5
6
4
2
Blue is the colour of the
clear sky and the deep sea
Red is the colour of danger
and courage
Black is the color of ebony
and of outer space
Yellow is the color of gold,
butter and ripe lemons
White is the color of milk
and fresh snow
Blue is the colour of the
clear sky and the deep sea
90. SWOT ANALYSIS
97
STRENGTHS
Blue is the colour of the clear
sky and the deep sea
WEAKNESSES
Yellow is the color of gold,
butter and ripe lemons
Black is the color of ebony
and of outer space
OPPORTUNITIES
White is the color of milk and
fresh snow
THREATS
91. BUSINESS MODEL CANVAS
98
Key Activities
Insert your content
Key Resources
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Value Propositions
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Customer Relationships
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Channels
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Customer Segments
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Key Partners
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Cost Structure
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Revenue Streams
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93. TEAM PRESENTATION
100
Imani Jackson
JOB TITLE
Blue is the colour of the clear
sky and the deep sea
Marcos Galán
JOB TITLE
Blue is the colour of the clear
sky and the deep sea
Ixchel Valdía
JOB TITLE
Blue is the colour of the clear
sky and the deep sea
Nils Årud
JOB TITLE
Blue is the colour of the clear
sky and the deep sea
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