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Medicine year 2 semester 2 > Case 25- calcium and old age > Flashcards

Case 25- calcium and old age Flashcards

1
Q

Bone formation and reabsorption- during life

A

1) During growth- rate of bone formation > resorption and skeletal mass increases
2) Once adult bone mass achieved. Rate of Formation = Resorption, maintain bone mass
3) From 30+ years- rate of resorption begins to > formation, bone mass slowly decreases
4) Bone formation and resorption occurs mainly in trabecular bone

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2
Q

Bone formation and reabsorption- Ca+2

A

1) 99% body Ca2+ in bone
most in hydroxyapatite crystals -Ca10(PO4)6(OH)2
2) Very little Ca2+ (<1%) can be released from bone
3) However, bone is the major reservoir of Ca2+ in the body
4) Bone- dynamic tissue
continually being formed and reabsorbed, remodeling, 10-15% of total adult bone mass turns over each year

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3
Q

The four cell types present in bone

A

1) Osteoprogenitor cells- stem cells, can differentiate into other bone cell types
2) Osteoblasts- synthesise the organic bone matrix (osteoid)
3) Osteocytes- inactive (mature) osteoblasts, become trapped in mineralised bone
4) Osteoclasts- erode mineralised bone and remodel, found on the surface of the sites of bone resorption

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4
Q

The interaction between bone cell types

A

Osteoprogenitors- differentiate into osteoblasts
Osteoblasts- synthesise and mineralise collagen to form osteoid. Inactivated to form osteocytes
Osteocytes- inactive osteoblasts- trapped within bone. Regulate activity of osteolasts
Osteoclasts- enzymatic resorption of bone in remodelling, are the differentiated blood monocytes

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5
Q

Osteobasts and osteocytes- growth:

A

Hormones act on osteoblasts, which in turn regulate osteoclastic activity

Osteoblasts produce osteoid component of mineralised bone matrix

As matrix is laid down osteoblasts become trapped within bone – osteocytes in lacunae

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6
Q

Osteoclasts- remodelling

A

1) During bone development, woven bone is eroded by osteoclasts activity and remodelled
2) Osteoclasts secrete= H+ and Cl- ions to create an acidic environment for solubilising the bone matrix. Cathepsin K protease into the subosteoclastic compartment to degrade collagen and proteins
3) The process is stimulated by the parathyroid hormone (PTH) and inhibited by calcitonin

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7
Q

Physiological actions of calcium

A

Calcium salts in bone- structural integrity of the skeleton

Calcium ions in extracellular and intracellular fluids

1) neurotransmitter release at synapse
2) blood coagulation
3) hormonal secretion
4) enzymatic regulation
5) muscle contraction

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7
Q

Physiological actions of calcium

A

Calcium salts in bone- structural integrity of the skeleton

Calcium ions in extracellular and intracellular fluids

1) neurotransmitter release at synapse
2) blood coagulation
3) hormonal secretion
4) enzymatic regulation
5) muscle contraction

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8
Q

Distribution of calcium in the body

A

Total body calcium (1-1.3 kg)
Bone- 99%
Body fluids- 1%, the majority is in intracellular fluid but some is in the plasma and interstitial fluid

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9
Q

Calcium levels are tightly regulated

A

For example:
1) If extracellular Ca2+ falls below normal
increased permeability of neuronal membranes to Na+, nervous system becomes progressively more excitable
2) Hyper excitability causes tetanic contractions
Hypocalcaemic tetany
3) Trousseau sign with hypocalcaemia- obstetric hand/carpopedal spasam

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10
Q

Calcium levels- A characteristic posture when the sphygmomanometer cuff is inflated above the systolic blood pressure

A

1) Wait 3 minutes
2) Flexion of wrist
3) Hyperextension of fingers and thumb

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11
Q

Organs involved with calcium homeostasis

A

1) Intestine- absorption/secretion
2) Kidney- filtration/reabsorption
3) Bone- formation/resorption

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12
Q

Calcium homeostasis (daily balance)

A 
Diet- 1000mg
Faecal excretion- 800mg
Urinary excretion- 200mg (2% of filtered load)
Bone cellular fluid- 1000mg
Rapidly exchangeable pool- 4000mg
Bone formation- 500mg
Bone resorption- 500mg
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13
Q

Intestinal calcium absorption

A

If concentration of calcium higher in lumen than in blood, can move into blood passively
But calcium often lower in blood so needs to be actively transported across basolateral wall of epithelium into blood

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14
Q

Function of calcium in the bone

A

Strengthens bone- structural

Integrity of skeleton

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15
Q

Enzyme which stimulates and inhibits bone resorption

A

Stimulates- PTH

Inhibits- Calcitonin

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16
Q

Cathepsin K protease

A

Enzyme secreted by osteoclasts which decrease collagen and protein

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17
Q

How is calcium transported in the blood

A

Most calcium is actively transported into the duodenum and jejunum epithelial cells from the lumen and then goes to the blood across the basolateral membrane

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18
Q

How is calcium moved from epithelial cells into the blood

A

Calbindin mops up calcium in the cell which helps to maintain concentration gradient
Calcium moves from epithelial cells into blood across basolateral membrane - calcium ATPase and Na/Ca exchanger

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19
Q

Calbindin

A

A vitamin K-dependent transport protein

Binds to calcium in cytosol of cells which means lower concentration so more can move into the cell by active transport

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20
Q

Kidneys in calcium homeostasis

A

Reabsorption of calcium- only 1% is lost in the urine
60% active transport in proximal tubule
30% passive diffusion in the loop of Henle
9% active transport in distal tubule

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21
Q

Regulating Ca+2 concentration

A

Non-hormonal= rapidly exchangeable pool (surface of skeleton) fast, but limited capacity
Hormonal=
1) Parathyroid hormone (PTH)
2) 1,25 dihydroxycholecalciferol (1,25 DHCC/ Calcitriol)
(cholecalciferol = vitamin D3)
3) Calcitonin

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22
Q

Parathyroid hormone (PTH)

A

1) Synthesised and secreted by the parathyroid glands; lie posterior to the thyroid glands
2) Chief cells= PTH synthesis
3) PTH is translated as a pre-prohormone (115 aa)
4) Following cleavage you have a biologically active peptide of 84 aa

23
Q

PTH function

A

1) To increase plasma (Ca+2)- Hypercalcaemic
2) The stimulus of PTH secretion is a decrease in plasma [Ca+2]
3) Secretion of PTH is inversely related to [Ca+2]

24
Q

PTH action on bone

A

1) Directly on bone to stimulate Ca2+ resorption- increase in osteoclast number, increase in osteoclast activity
2) Directly on bone to decrease collagen synthesis by osteoblasts (i.e. decrease bone formation)

25
Q

PTH action on the kidneys

A

1) Directly to stimulate Ca2+ reabsorption in the distal tubule
2) Directly to stimulate the activity of 1alpha-hydroxylase, which catalyzes the formation of 1,25 DHCC from Vitamin D

26
Q

PTH action on the intestine

A

1) Has no direct effect

2) Acts indirectly by stimulating 1,25 DHCC synthesis- stimulates calcium absorption

27
Q

1,25- dihydroxycholecalciferol

A

The active form of vitamin D

Needs help from 1-α hydroxylase to convert vitamin D3 to 1,25 DHCC

28
Q

Role of 1,25 DHCC

A

Stimulates calcium absorption and increases plasma calcium concentration
How it works- Greater expression of calbindin so helps to sequester larger amounts of Ca - increases capacity of epithelial cell to pull Ca out of lumen so increased concentration in epithelial cells to be actively transported into the blood

29
Q

Role of 1,25 DHCC

A

Stimulates calcium absorption and increases plasma calcium concentration
How it works- Greater expression of calbindin so helps to sequester larger amounts of Ca - increases capacity of epithelial cell to pull Ca out of lumen so increased concentration in epithelial cells to be actively transported into the blood

30
Q

MOA of 1,25 DHCC

A

Kidney- Increases tubular reabsorption of calcium, relatively minor effect
Bone- promotes action of PTH, relatively minor. Net effect=resorption
Intestine- main action is on the intestine, increases calcium reabsorption

31
Q

Calcitonin

A

Synthesised and secreted by parafollicular C cells of the thyroid
Major stimulus of calcitonin secretion increases plasma calcium levels
Calcitonin is a physiological antagonist to PTH with regard to calcium homeostasis

32
Q

Main target of calcitonin

A

Bone

  • mainly osteoclast
  • inhibits osteoclast motility and cell shape
  • inactivates cell
  • major effect is a rapid decrease in calcium inhibition of bone resorption
  • inhibits bone removal, promotes bone formation
33
Q

Effect of calcitonin

A

Kidney- decrease tubular reabsorption of calcium (weak effect)
Intestine- no effect

34
Q

Role of calcitonin in human calcium homeostasis

A

Very minor role
Chronic excess does not produce hypocalcaemia
Removal of parafollicular cells does not cause hypercalcaemia
May be more important in bone remodelling than in calcium homeostasis

35
Q

PACism: life expectancy and multimorbidity

A

• In 2015 life expectancy at 65 was +18.6 (men), +21.1 (women) – most
of these years are spent with 1 or 2 diseases
• By 2035 life expectancy at 65 will be higher, but with more time spent
with MLTCs (2+ diseases)

36
Q

PACSim support needs

A

Between 2015 and 2035 absolute numbers of people 65+ will
increase by 48.6%
• Numbers of people 65+ living independently will increase 61%

37
Q

Older people and health globally

A 
• Overall life expectancy increasing 
faster than healthy life expectancy
• Increase in chronic non-communicable diseases (NCDs)
• Scope for prevention eg treatment 
of hypertension 
• Social and economic benefit
• Traditional care systems may not 
meet needs for NCDs eg dementia
38
Q

Attitudes and culture- Ageing

A

1) Attitudes improving but ongoing evidence of ageism and negative stereotyping, including in healthcare
2) This is seen in Workplace discrimination, Gender-based abuse and a Lack of prioritisation in policy

39
Q

Changing healthcare needs of the elderly

A 
• Changing “frontline” 
presentations (GP, A and E)
• Lack of guidelines and 
infrastructure appropriate 
for multimorbidity
40
Q

Elderly- Changing frontline presentations

A 
• Numbers of older people 
presenting to A and E are rising 
disproportionately to increases 
in the population
• Older people are likely to 
spend longer in A and E and are 
more likely to be admitted
41
Q

Elderly- system challenges

A 
• NHS historically set up to deal with 
single system conditions (eg cardio or
GI or respiratory) rather than 
multimorbidity
• Research and guidelines based on 
single conditions in younger 
populations (OP excluded)
• Lack of guidance and evidence base in 
relation to OP with complex 
pathologies
• Lack of service integration
42
Q

Policies aiming to improve healthcare OP

A

1) Kings fund (2014)

2) NHS long term plan (2018)

43
Q

Kings fund

A 
King’s Fund (2014) – evidence 
synthesis:
• Shift from high cost reactive care to 
preventative and supportive care
• Continuity of care (eg GP)
• Prevention through lifestyle change
• Comprehensive Geriatric 
Assessment (CGA)
• Successful interventions
44
Q

Comprehensive Geriatric assessment (CGA)

A

• Moves forward from the biopsychosocial
model
• Person-centred
• An approach to managing MLTCs
• Requires the complementary skills of the
MDT to make a truly holistic assessment
• Different settings e.g. emergency care,
community, day hospital
Established evidence bases, results in a reduced- Length of stay, Costs, Admission to longterm care, Post-operative complications

45
Q

NHS long term plan (2018)

A

1) New service model- community based MDT teams
2) Social prescribing
3) ‘Same day’ emergency care/CGA
4) Integration of health and social care
5) Prioritise prevention- smoking, alcohol, air pollution, inequalities, screening

46
Q

Ageing and ethics

A

1) Consent and capacity
2) End of life care and resuscitation
3) When to investigate and when to pallitate (risk/benefit balance)

47
Q

Ageing and clinical research

A

1) Research is most often condition or systems based
2) Older people are often excluded from trials
3) Lack of evidence in relation to multi-morbidity (at any age)
4) Disproportionate concern about risk

48
Q

Frailty

A 
A medical syndrome with multiple
causes and contributors that is 
characterized by diminished strength, 
endurance, and reduced physiologic 
function that increases an individual’s 
vulnerability for developing increased 
dependency and/or death
48
Q

Frailty

A 
A medical syndrome with multiple
causes and contributors that is 
characterized by diminished strength, 
endurance, and reduced physiologic 
function that increases an individual’s 
vulnerability for developing increased 
dependency and/or death
49
Q

Examples of frailty

A

Neurology- slower reaction time
Cardiovascular- heart valve calcification
Psychiatry- loss of neurons and brain mass

50
Q

Why measure frailty

A

1) Identification of older people ‘at risk;
2) Planning services, support and recources- Immediate, long term
3) Intervention to prevent morbidity/mortality- Physical activity, dietary supplementation, reduction of polypharmacy
4) Improves quality of life

51
Q

How can we measure frailty

A

2 main academic models:

1) Frailty phenotype (Fried)- rule based ‘objective’
2) Frailty index (Rockwood)- deficit model ‘subjective’

52
Q

How can we measure frailty

A 
Choice depends on context (eg):
• Rockwood Clinical Frailty Score 
(CFS)
• Gait speed/TUG
• Self-report eg PRISMA-7
53
Q

How should we care for older people with frailty and MLTCs?

A 
Holistic, integrated approach 
(person, pathology, environment)
Person-centred care:
• Dignity respect and compassion
• Care co-ordination and transition
• Personalised (not standardised by 
disease)
• Enabling (not disabling)
Multidisciplinary>CGA

Medicine year 2 semester 2 (47 decks)

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