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Patho > Osteoporosis > Flashcards

Osteoporosis Flashcards

1
Q

What’s the difference between osteoporosis and osteoarthritis?

A

Osteoporosis is a metabolic bone disorder where there’s a reduction in bone mass (density) because of an imbalance in bone remodeling. There’s faster bone resorption as opposed to bone formation and bones then break more easily.

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2
Q

What’s a T score?

A

It’s a measurement of bone mineral density. -1 to -2.5 is osteopenia. anything greater than -2.5 is considered osteoporosis. It’s a radiographic test.

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3
Q

What is bone remodeling?

A

It’s the breaking down of bone (resorption) and the building of new bone (bone deposition)

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4
Q

What does an osteoclast do?

A

It breaks down bone. Contributes to bone resportion through acids, and enzymes.

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5
Q

What does an osteoblast do?

A

It’s an immature bone cell that build bone matrix and contributes to bone deposition.

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6
Q

What sort of bone cell carries RANKL?

A

An osteoblast

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7
Q

What controls osteoclasts?

A

Osteoblasts.

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8
Q

What is RANK and where is RANK found?

A

RANK is a receptor on the osteoclasts and their precursors. When RANKL plugs into RANK then it triggers the osteoclast to break down bone.

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9
Q

What does OPG stand for?

A

Osteoprotegrin

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10
Q

What is the function of OPG?

A

It protects against bone loss by plugging into RANK receptors and that inhibits osteoclast formation and activation.

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11
Q

What are the steps in bone remodeling?

A

An osteoclast breaks down bone (resorption), macrophages come along and clear the debris - that’s called reversal. Osteoblasts make bone (formation). Calcium and phosphate are added to the bone (mineralisation), and then quinessense.

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12
Q

Where does bone remodelling occur?

A

Along the free surface of central canals in compact bone or trabeculae in spongy bone.

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13
Q

What are osteocytes?

A

Mature bone that maintain bone matrix and health

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14
Q

What are osteoprogenitor cells?

A

Stem cells that divide and produce osteoclasts?

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15
Q

What is the extracellular matrix made up of?

A

Type I collagen fibres and calcium phosphate cells.

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16
Q

What’s the function of type I collagen fibres?

A

Provides tensile strength that resists pulling and twisting forces - like a cable.

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17
Q

What role do calcium and phosphate salts play in the extracellular bone matrix?

A

Calcium phosphate salts deposit around collagen fibres and provide rigidity which resists compressive forces.

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18
Q

Bendy bones (like in rickets) is due to what?

A

Impaired mineralization.

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19
Q

Fragile bones (like in osteogensis imperfecta) are due to what issue?

A

Collagen is defective.

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20
Q

What are 3 functions of bone remodeling?

A

1) Maintains the quality of bone
2) Provides access to skeletal mineral stores like calcium and phosphate.
3) Strengthens bone in areas of stress or #

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21
Q

Low levels of RANKL and high levels of OPG would promote or inhibit bone breakdown/resorption?

A

It would inhibit bone resorption.

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22
Q

High levels of RANKL and low levels of OPG would promote or inhibit bone break down/resorption?

A

It would promote resorption.

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23
Q

What are some factors that increases RANKL and decreases OPG?

A

Parathyroid hormone, calcitriol, glucocorticoids, PGE2, Interleukin 1

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24
Q

What are some factors that decrease RANK and increase OPG?

A

Estrogen.

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25
Q

Denosumab interferes with RANK/RANKL/OPG system to treat osteoporosis. What does it do?

A

Mimics OPG, blocks RANKL receptor.

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26
Q

When does peak bone mass start to decline?

A

Age 30. You lose about 0.5% each year.

27
Q

What factors contribute to weaker bone mass?

A

Poor nutrition, lack of exercise, smoking, drinking during adolescence

28
Q

What causes Type one (“post menopausal”) Osteoporosis?

A

Occurs in women between the ages of 50-70 due to loss of estrogen. Remember, estrogen increases OPG and decreases RANKL, so it inhibits osteoclast activity

29
Q

What happens to bones in menopause?

A

No increased OPG, and so RANKL is not inhibited.

30
Q

What are some good things about hormone replacement therapy?

A

Strengthens bones, lowers LDL cholesterol, raises HDL cholesterol, reduces menopausal symptoms like hot flashes.

31
Q

What are some bad things about hormone replacement therapy?

A

Increased risk of breast cancer, increased risk of uterine cancer, increased risk of blood clots.

32
Q

What is type 2, AKA age related/senile osteoporosis?

A

It’s bone loss due to aging and happens after the age of 70. Decreased capacity of cell division and synthesis of the bone matrix. Decreased activity of enzymes needed for vitamin D activation (alpha 1 hydroxylase)

33
Q

What’s the function of vitamin D??

A

Enhances uptake of calcium, maintains calcium balance in body.

34
Q

What sort of food has vitamin D?

A

eggs, liver, oily fish, fortified foods like milk and cereal, supplements

35
Q

Where can we get our major source of vitamin D?

A

Sunlight. There’s a vitamin D precursor made from cholesterol that’s stored in our skin. When UV light touches it, it converts it to vitamin D3.

36
Q

What role do the liver and kidneys play in making calcitriol?

A

Liver and kidney enzymes convert D3 to calcitriol.

37
Q

Your patient doesn’t have enough vitamin D, how does this affect their calcium and parathyroid hormone?

A

When vitamin D is low, blood calcium levels fall and PTH is released to stimulate bone resorption (breakdown) and kidneys reabsorb calcium, and the kidneys excrete phosphate.

38
Q

What is secondary osteoporosis?

A

When there’s an underlying disease or deficiency or drug that affects bone remodelling.

39
Q

What are some examples of conditions that cause secondary osteoporosis? THINK HANG LAMP

A

Hormone factors
Alcohol and smoking
Nutrition
Genetics

Low peak bone mass
Age
Medications
Physical factors

40
Q

What causes prolonged calcium deficiency?

A

Not enough dietary intake (like due to poor nutrition, eating disorders) and impaired absorption (like a lot of caffeine >4 cups/day, celiac dx, malabsorption syndromes and the elderly.

41
Q

How does your parathyroid respond to decreased calcium in the blood?

A

Pumps out more parathyroid hormone.

42
Q

What other nutrients help sythesize osteoid in bones?

A

Proteins and vitamin C

43
Q

What genetic conditions could affect peak bone mass?

A

Conditions that affect Estrogen receptors, type 1 collagen, OPG, or RANKL. Also if someone has a thin build, or is caucasian/asian.

44
Q

What stimulates osteoblast activity?

A

Stress applied to bone like from walking or weight training.

45
Q

What contributes to “disuse osteoporosis”?

A

Inactivity due to bed rest, paralysis, arthritis, sedentary lifestyle.

46
Q

Why would elite female endurance athletes be at risk of osteoporosis?

A

You need to have a certain amount of body fat to produce estrogen and to stimulate OGP and inhibit RANKL, and these athletes wouldn’t have enough body fat to produce sufficient estrogen.

47
Q

What is leptin?

A

It’s an adipokine released from fat cells that regulates the appetite and metabolism. If you are fasting, you will have decreased leptin and so your appetite will increase and you will have decreased energy expenditure. If you are eating a bunch, you will have increased leptin, and decreased appetite and increased energy expenditure.

48
Q

Other than controlling appetite and metabolism, what else does leptin do?

A

It increases the secretion of GnRH which affects LH and FSH. If there’s not enough leptin, then it causes you to become amenorrheic. If someone has no period for 6-12 months then they’re at risk for osteoporosis.

49
Q

How would hyperthyroidism affect bone resorption and risk of osteoporosis?

A

It would increase bone turn over so it would increase risk of osteoporosis and increase resorption. Example: grave’s dx, thyroid adenoma, high dose thyroid meds.

50
Q

How would hyperparathyroidism affect osteoporosis?

A

It would increase risk, by increasing resorption Example: benign parathyroid tumor, or ectopic production by a malignant tumour

51
Q

How would androgens affect risk of osteoporosis?

A

Decreased androgens would increase the risk of osteoporosis in men. Conditions like pituitary adenoma, or conditions affecting the testes.

52
Q

How would cortisol increase osteoporosis?

A

Increase the risk of osteoporosis because it would affect the collagen of the bone. Ex: pituitary adenoma, adrenal adenoma, ACTH production by a lung tumour.

53
Q

What medication most commonly causes medication induced osteoporosis? (causes increased RANKL, and decreased OPG)

A

Corticosteroids

54
Q

Why might diuretics cause osteoporosis?

A

You may lose calcium in the urine, decreased calcium means decreased calcium to your bones and demineralization of bone

55
Q

Why might breast cancer drugs cause osteoporosis?

A

Some drugs like aromatase inhibitors inhibit estrogen production which is needed to inhibit RANKL and increase OPG.

56
Q

What type of bone is affected faster by osteoporosis - spongy or compact?

A

Spongy because of increased surface area.

57
Q

Can someone tell that they have osteoporosis?

A

Not until there’s a fracture.

58
Q

What are some common areas to get pathologic #?

A

Vertebrae, hip (neck of the femur), and wrist

59
Q

Your patient has trouble breathing, heart burn and their ribs can touch their pelvic bones all related to osteoporosis, what are these symptoms of?

A

Thoracic vertebrae fractures.

60
Q

Your elderly pt has noticed a change in her appetite recently. She said she’s constantly feeling bloated, it doesn’t take much to make her full and she’s frequently constipated. What could be causing these symptoms?

A

Lumbar Fractures.

61
Q

When would we order a bone marrow density test?

A

If the pt is older than 65 years, or at moderate risk for a fracture within 10 years. There’s an online fracture risk calculator.

62
Q

Would an X-Ray or CT scan be appropriate?

A

Yes both tests can diagnose osteoporosis

63
Q

At what point could osteoporosis show up on an xray? How much of the bone would need to be missing?

A

1/3

64
Q

What is some good advice to give someone if they want counselling on how to avoid osteoporosis?

A

Reduce smoking, etoh and certain meds, diet rich in vit d and protein and calcium, regular exercise (wt bearing and muscle strengthening, Fall prevention strategies, and pharmacologic therapy like drugs that block bone resorption and those that stimulate bone formation.

Patho (12 decks)

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