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LIFESCI 3AA3 > TOPIC FIVE: BONE HEALTH > Flashcards

TOPIC FIVE: BONE HEALTH Flashcards

1
Q

Are hip fractures expensive

A

Yes! Cost $27 000 to treat

Big impact on healthcare services

Link between fractures, risk of death and healthcare services

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2
Q

Prevalence of osteoporosis in men and women

A

1/3 women
1/5 men

there is a role of estrogen

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3
Q

Is there an effect on QoL with osteoporosis?

A

Yes

After someone has experience a fracture, there is a decrease in physical function, there is a greater change in pain, there is a change in general health, vitality, social function, mental health

Seems to affect people for a number of different reasons

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4
Q

What is osteoporosis

A

Low bone mineral density and microarchitecture deterioration resulting in risk of fracture

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5
Q

What is more commonly used to diagnose osteoporosis - BMD or microarchitecture

A

BMD

The microarchitecture deterioration is harder to use to diagnose and is often less considered in osteoporosis

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6
Q

What is the structure of the inside of bone

A

There is a cortical shell and a bone that looks like honeycomb made up of trabeculae

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7
Q

What is trabeculae important for

A

Bone strength

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8
Q

What is there an imbalance of in osteoporosis

A

Bone resorption and bone formation

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9
Q

What is used along with BMD to diagnose these days

A

Used to just use BMD to diagnose osteoporosis but now also use risk factors to predict the risk of fracture

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10
Q

How many SD decrease in BMD is indicative of increased fracture risk

A

1 SD decrease in BMD in any site increases the risk of fracture

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11
Q

What are the most common site to test BMD

A

Wrist
Hip
Vertebrae

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12
Q

What are the main osteoporotic fractures

A

Vertebral fracture
Hip fracture
Wrist fracture
Proximal humerus fracture

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13
Q

What is the wrist fracture usually referred to as

A

The lucky break

Individuals with wrist fracture may go on to be assess for osteoporosis and are often treated which may prevent them from having a more detrimental fracture

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14
Q

What is DXA

A

Dual x-ray absorptiometry

Used to measure BMD

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15
Q

What is best at predicting fracture risk

Just clinical factors
Just BMD
Clinical factors + BMD

A

Clinical factors + BMD

Has the highest sensitivity to specificity

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16
Q

What is a T score

A

When someone gets a BMD test done, there results are presented as a T score

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17
Q

What does a positive T score mean

A

suggesting that the bone health is better than premenopausal bone density

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18
Q

What does a negative T score mean

A

suggesting that the bone health is worse than premenopausal bone density

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19
Q

What does a lower T score mean

A

A lower (more negative T score) puts the risk of fractures even higher

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20
Q

When do we achieve peak bone health

A

20s

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21
Q

What happens 5-7 years around menopause (%)

A

There is a steep loss of bone density (12%)

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22
Q

Other risk factors for decrease bone health

A

lack of exercise, poor nutrition, loss of testosterone

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23
Q

What is the T score used to diagnose osteoporosis

A

-2.5

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24
Q

What is the T score used to diagnose osteopenia

A

-2.5 to -1

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25
What is the issue with just using T scores to diagnose
People within the osteopenia and the normal range also fracture their bones so we can see using BMD only is not the best
26
What is the relationship between medication and fracture risk
There is a really big reduction in fracture risk with only a small amount in change in BMD Maybe the medication are helping something else
27
What are limitations to BMD
It is 2D (missing volumetric assessment) Does not tell us about cortical and trabecular bone architecture There can be artifacts that the bone scan picks up (could be osteophytes)
28
What are osteophytes
Abnormal bone growth that develops due to bone on bone contact Common in osteoarthritis and type 2 diabetes
29
What are the main components of bone and the %
40% proteins (T1 collagen) 60% mineral (hydroxyapatite which Ca is apart of) There is a balance between having enough protein and mineral in bone to allow to ben when you apply load Proteins allow bend Minerals allow hardness
30
What are structural bone qualities
Bone size, shape Cortical thickness and porosity Trabecular boen microarchitecture
31
What are mineral bone qualities
``` Crystallinity Osteon count Collagen cross-links Microdamage Mineralization ```
32
What is the rate of bone turnover
10% of your skeleton is completely turned over each year Every 10 years, you will have a new skeleton The process of resorption and formation takes 3-6 months
33
What are osteoblast
Build bone
34
What are osteoclasts
Break bone
35
Communication between osteoblasts and osteoclasts
When the osteoclasts go into absorb the bone, they communicate to the osteoblast to go in and add more osteoids to the bones The osteoid becomes mineralized and becomes bone
36
What are the four stages of bone remodelling
Resportion - reversal - formation - resting
37
Why does bone remodelling take place
To release Ca stored in bone if there is not enough in the diet 99% of Ca in our body is stored in bones and Ca is extremely important for many processes
38
What are mirocracks
Every time we but load on our bones, we are stimulating this process to take place - We create microcracks when we apply load which is a health process which stimulates resportion and formation of new bone
39
What cells do osteoclast originate from
Hematopoietic stem cells
40
What cells do osteoblast originate from
Mesenchymal stem cells
41
What do osteoclast secrete
Osteoclasts secrete HCl, Cathepsin K and MMP to break down the bones
42
What do osteoblasts secrete
Osteoblasts secrete osteocalcin, alkaline phosphatase osteoid, hydroxyapatite to build the bone
43
What are the pathways that trigger osteoblast activity
Runx2 is a transcription factor that stimulates osteoblast formation The Wnt formation also increases osteoblast proliferation from MSC Scleostin turns off osteoblast formation by downregulation of the Wnt pathways to prevent excessive bone formation
44
What are pathways that trigger osteoclasts
RANKL (receptor activator of nuclear factor kB ligand) turns on the activation of osteoclasts CSF (Colony stimulating factor) turns on the production of osteoclasts from the stem cells
45
What is Cleidocranial dysplasia
Mutation on Runx2 gene Hypoplasia of clavicles and bones in face Sunk in clavicles Not as much bone formation
46
What is Van Buchem disease
Mutation on SOST gene - This gene is the sclerostin encoding gene Hyperostosis of mandible, skull, ribs, long bones Excessive bone formation
47
Is there increased of decrease bone resorption after menopause
Increased When women lose estrogen, there is increase in bone resorption
48
What happens when women are prescribed estrogen or progesterone What is the mechanism
Women prescribed estrogen and progesterone have decrease fracture risk Estrogen decreases the production of RANKL and CSF
49
What do corticosteroids do to bone (mice and humans)
In the mice, there is more osteoblasts in the control group vs. the treatment with prednisolone • 86% reduction In the humans, there is decrease in BMD of the lumbar in the corticosteroid group
50
What is the mechanism behind corticosteroids and bone
Glucocorticoids inhibit the WNT pathway and therefore limit the production of osteoblasts that mature
51
What happens when we load out bones/do exercise
Every time we move our bodies, we have microcracks which promote bone growth When we move, we have fluid that flows through the canaliculi in the bones. The fluid stimulates osteoblasts to build bone Increasing pressure applied to the bone increase the amount of bone formed
52
What is the mechanism behind exercise and bone health
Fluid flows through the bone which stimulates osteoblasts When you flex muscles there is a release of growth hormone which stimulates osteoblasts
53
What is Wolffs law
When you load bone, it will get stronger
54
Is estrogen protective for bone health? How?
Yes | Limits bone resorption
55
Estrogen wrt osteoclast
Estrogen inhibits RANKL and CSF
56
What does Ca and vitamin D do in terms of osteoblasts
Stimulate formation of osteoblasts
57
What does glucocorticoids do wrt osteoblast
Inhibit the Wnt pathway
58
Do individuals with diabetes have higher or lower T scores
Higher! Individuals with diabetes seem to have better bone density (higher bone density)
59
Mechanism wrt diabetes and bone density
Obesity and type 2 diabetes often go together Obesity can cause increase leptin (hormone secrete from adipocytes) which stimulates osteoblast and decreased RANKL Hyperinsulinemia may develop from insulin medication, or high levels of blood glucose - insulin stimulates IGF (insulin like growth factor) which stimulates osteoblast cells
60
Do individuals with diabetes have a higher or lower fracture risk
Higher
61
Mechanism wrt to diabetes and higher fracture risk
Insulin is a marker for diabetes duration someone who has had diabetes for longer maybe they are more prone to falls due to the muscle impairments and neuropathy maybe the diabetes might affect bone quality?
62
What component of bone is greater in individuals with diabetes
Individuals with diabetes had more mineralized bones compared to those without diabetes The holes in the trabeculae were actually larger The increase in bone mineralization might be due to a suppression of bone turnover - more mineralized might make it more brittle
63
Does medication for osteoporosis work for patients with diabetes
No The risk of fracture is higher than those without diabetes

LIFESCI 3AA3 (6 decks)

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