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Musculoskeletal Physiopathology > Metabolic Disorders of Bone > Flashcards

Metabolic Disorders of Bone Flashcards

1
Q

What are some metabolic disorders of bone?

A
  • Osteoporosis
  • Vitamin D deficiency
  • Vitamin D toxicity
  • Vitamin C deficiency
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2
Q

When does the amount of bone in the body peak in life?

A

Around 25-35 years

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3
Q

What are some factors that influence higher bone mass/density peak?

A
  • Males have higher peak in mass
  • Ethnicity/genetics
  • Activity
  • Nutrition
  • Hormones
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4
Q

After 35(ish), there is a decline of bone density for both sexes
Who will decline first?

A

Females lose density about 10 earlier than males

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5
Q

What is the organic: inorganic ratio of bone in children?
How does this affect the structure and function of bones?

A

1:1
Lots of collagen, flexible/springy bones

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6
Q

What is the organic: inorganic ratio of bone in adults?
How does this affect the structure and function of bones?

A

1:4
Bones are hard, but have some give

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7
Q

What is the organic: inorganic ratio of bone in elderly (65+)?
How does this affect the structure and function of bones?

A

1:7
Bones lack collagen, no spring, more fragile

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8
Q

How does age affect our ability to make collagen?

A

Less able to make collagen as we age

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9
Q

What are some examples of decreased synthesis etiologies that decrease bone density?

A
  • Decreased osteoblastic function: organic to inorganic ratio is maintained
  • Decreased ability to make collagen with age, so less organic material to mineralize
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10
Q

The lack of ___ or ___ will decrease mineralization of osteoid

A

lack of Vitamin D or calcium

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11
Q

What conditions come of a lack of Vitamin D or calcium?

A

Osteomalacia, hyperparathyroidism

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12
Q

What shift in activity of bone cells will cause increased destruction of bone density?

A

Balance of osteoclastic to osteoblastic activity

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13
Q

What is osteoporosis?

A

Decreased bone mass with normal quality (normal organic:inorganic ratio) where bones weaken

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14
Q

What is osteomalacia?

A

Vitamin D deficiency
Decreased bone mass with increased organic:inorganic ratio; decreased mineralization of osteoid; bones soften and weaken

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15
Q

Primary osteoporosis involves a change in what balance?

A

Osteoblast:osteoclast balance

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16
Q

What is type 1 primary osteoporosis?

A

Post-menopausal osteoporosis

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17
Q

How can post-menopause lead to type 1 primary osteoporosis?

A

Estrogen drop increases osteoclast activity

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18
Q

What is type 2 primary osteoporosis?

A

Senile osteoporosis: age related loss of osteoblast function

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19
Q

Besides decreased estrogen post-menopause and age related factors, what are some contributors to primary osteoporosis?

A
  • Vitamin D
  • Calcium intake and absorption (calbindin)
  • Exercise
  • Smoking
  • Hypogonadism
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20
Q

In short, what is the function of estrogen in bone?

A

Major hormonal regulator of bone remodeling in both sexes

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21
Q

How does estrogen affect osteoclasts?

A

Blocks RANKL, suppressing osteoclastic activity

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22
Q

How does estrogen affect osteoblasts?

A

Inhibits osteoblast apoptosis and increases osteoblast lifespan

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23
Q

How does estrogen affect cytokines?

A

Decreases the production of bone-resorbing cytokines: IL-1, IL-6, TNF-a, and prostaglandins

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24
Q

How does hormone replacement therapy (HRT) affect bone for postmenopausal women with primary osteoporosis?

A
  • Increased circulating calcitriol (tries to increase calcium)
  • Increased calcium absorption
  • Slows loss of bone, does not contribute to rebuilding
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25
Q

What is the effect of biphosphonates for primary osteoporosis?

A
  • Decrease osteoclastic resorption, does not increase deposition
  • Reduces risk of fracture, especially vertebral
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26
Q

What hormone plays a similar role to estrogen in bone?

A

Androgen

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27
Q

Besides estrogen, what are some important hormones for bone?

A
  • Androgen
  • Parathyroid hormone (PTH)
  • Calcitonin
  • Thyroid hormone
  • Growth hormone
  • Glucocorticoids
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28
Q

Where does calcitonin come from in the body?

A

Thyroid gland

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29
Q

Where does growth hormone come from in the body?

A

Pituitary gland

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30
Q

Where do glucocorticoids come from in the body?

A

Adrenal glands

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31
Q

How does primary osteoporosis affect ESR (erythrocyte sedimentation rate)?

A

Increases/elevates

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32
Q

What does primary osteoporosis mean for calcium levels?

A

Low levels of calcium in bone

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33
Q

What does primary osteoporosis mean for phosphate levels?

A

Higher phosphate levels (low calcium)

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34
Q

How does primary osteoporosis affect alkaline phosphatase?

A

Increased/elevated

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35
Q

What are some exogenous causes of secondary osteoporosis?

A
  • Disuse
  • Endocrine and genetic abnormalities or malabsorption issues
  • Chronic corticosteroids
  • Multiple myeloma
  • Complex regional pain syndrome
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36
Q

How can disuse due to casting affect bone?

A

Secondary osteoporosis with radiographically visible bone loss in 7-10 days, peaks 2-3 months

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37
Q

What are some examples of endocrine and genetic abnormalities or malabsorption issues that lead to secondary osteoporosis?

A
  • Osteomalacia
  • Hyperparathyroidism
  • Cushing disease
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38
Q

How does chronic corticosteroid use, such as with prednisone, lead to secondary osteoporosis?

A

Inhibits osteoblastic activity, impairs calcium absorption

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39
Q

How does multiple myeloma lead to secondary osteoporosis?

A

Osteoblast inhibiting hormone released

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40
Q

What is the most significant clinical implication of osteoporosis?
How prevalent is this?

A

Increased fracture risk:
50% of women over 50 will have an osteoporotic fracture
20% of men over 50 will have a osteoporotic fracture

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41
Q

Which bones are most at risk for osteoporotic fracture?

A
  • Hip
  • Spine (compression fractures)
  • Distal radius
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42
Q

What is the frequency of osteoporotic fracture of the hip in elderly patients?

A

250,000-300,000 in the US per year

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43
Q

With osteoporosis, ___ are dead within a year

A

25%

44
Q

With osteoporosis, ___ are in a nursing home within a year

A

25%

45
Q

With osteoporosis, ___ have some degree of limitation
Only ___ of elderly with a hip fracture can walk unaided across a room in one year

A

50% have limitation
only 15% can walk within a year

46
Q

What are the fiscal implications of osteoporosis?

A

It is costly, more fractures will be more expensive

47
Q

What is the purpose of radiographs for osteoporosis?

A

Primarily, visualizing fractures, but also finding osteopenia
Poor for assessing bone density

48
Q

What imaging is used to quantify bone density?

A

Bone densitometry (dual energy X-ray absorptiometry (DEXA))

49
Q

What are the two readings of DEXA (bone densitometry)?

A
  • T-score
  • Z-score
50
Q

What does the T-score of DEXA indicate?

A
  • Bone density compared with 18-25 year old of same race and sex
  • Gives risk of fracture
51
Q

What does the Z-score of DEXA indicate?

A
  • Bone density compared with other people of same age, race, and sex
  • Useful for premenopausal evaluation of density
  • Useful for female athlete triad
52
Q

What is the female athlete triad?

A
  • Disordered eating (low energy)
  • Amenorrhea (menstrual dysfunction/absence)
  • Osteoporosis
53
Q

What T-score readings of DEXA are normal, osteopenia, and osteoporosis?

A

+1 to -1 considered normal
-1 to -2.5 osteopenia
-2.5 or less osteoporosis

54
Q

How does a DEXA T-score values influence fracture risk?

A

-2 = 4x more likely
-3 = 8x more likely
-4 = 16x more likely
(exponents of 2)

55
Q

What is Dowager’s Hump?

A

Osteoporotic hyperkyphosis leading to multiple compression fractures

56
Q

Where does a Colles fracture occur?

A

Distal radius

57
Q

What are four treatments for osteoporosis?

A
  • Fall prevention
  • Exercise
  • Diet
  • Drug/supplement therapy (HRT, calcitonin, bisphosphonates)
58
Q

Can a chiropractor treat an osteoporotic patient?

A

Yes, can treat osteoporotic patients, but cannot directly treat osteoporosis

59
Q

What are two vitamin D disorders?

A
  • Hypovitaminosis D
  • Hypervitaminosis D
60
Q

What are two results of hypovitaminosis D?

A
  • Osteomalacia
  • Rickets
61
Q

What is osteomalacia?
What age group does it usually affect?

A

Decreased calcium absorption in the gut, inadequate mineralization of osteoid
Found in adults

62
Q

What is rickets?
What age group does it usually affect?

A

Children/individuals with open growth plates
Inadequate cartilage and bone formation at the growth plate

63
Q

What are some ways to acquire vitamin D deficiency?

A
  • Inadequate sun
  • Inadequate dietary intake
  • Decreased absorption
64
Q

What are some ways to inherit vitamin D deficiency?

A
  • Vitamin D-dependent rickets type I
  • Vitamin D-dependent rickets type II
65
Q

How does vitamin D-dependent rickets type I cause deficiency?

A

Defective hydroxylation of metabolites in liver or kidney

66
Q

How does vitamin D-depending rickets type II cause deficiency?

A

End organ insensitivity to vitamin D

67
Q

What are some etiologies of vitamin D deficiency that aren’t acquired or inherited?

A
  • Tumor related osteomalacia (multiple endocrine neoplasia)
  • Chronic renal disease
  • Cirrhosis
  • Anticonvulsant medications
68
Q

How does decreased calbindin production affect absorption in the GI?

A

Decreased absorption of calcium and phosphate

69
Q

If plasma levels of calcium decrease, what secretion increases in response?

A

PTH secretion increases

70
Q

Decreased calcitriol (active vitamin D) means less ___ retrieved from bone

A

less calcium

71
Q

In the kidney, ___ is excreted in urine and ___ is mostly retained

A

phosphate is excreted in urine and calcium is mostly retained

72
Q

Long term, vitamin D deficiency will result in ___ in phosphate and ___ in calcium levels

A

dramatic decrease in phosphate and modest decrease in calcium levels

73
Q

What is the net effect of vitamin D deficiency on bone?
Why?

A

Decrease in bone mineralization
Excessive osteoid accumulates and is not well mineralized due to low levels of calcium and phosphate

74
Q

What is the diagnostic profile shared between acquired vitamin D deficiency and vitamin D-dependent rickets type I?

A
  • Slightly reduced plasma calcium
  • Greatly reduced plasma phosphate
  • Elevated levels of PTH
  • Increased alkaline phosphatase
75
Q

What is the treatment for the diagnostic profile of acquired or vitamin D-dependent rickets type I?

A

Megadosing vitamin D (Rx grade) or provide end stage metabolites

76
Q

With osteomalacia, there is a relative ___ in organic and ___ in inorganic bone constituents

A

increase in organic and decrease in inorganic

77
Q

Which vitamin D deficiency has marked, generalized osteopenia due to defective of mineralization of bone in adults?

A

Osteomalacia

78
Q

The following describes the clinical manifestations of what disease?

  • No symptoms early
  • Eventually, dull, aching bone pain
  • Lower back, pelvis, hips, legs, ribs pain
  • Pain may be worse at night or weight bearing
  • Muscle weakness
  • Patient adopts a waddling gait due to decreased muscle tone and leg weakness
A

Osteomalacia (a vitamin D deficiency)

79
Q

What are some radiographic findings of osteomalacia?

A
  • Generalized osteopenia
  • Pseudofractures
  • Corticomedullary indistinction
  • Reversible, no/minimal deformity
80
Q

What are four causes of pseudofractures?

A

PROF:

  • Pagets
  • Rickets
  • Osteomalacia
  • Fibrous dysplasia
81
Q

What are the pseudofractures found in osteomalacia?

A

Unmineralized osteoid seam

82
Q

With rickets, there is lack of control over…

A

endplate growth

83
Q

With rickets, decreased ___ and ___ contribute to lack of control over endplate growth

A

decreased cartilage formation and osteoid mineralization

84
Q

Which disease presents with the following radiographic findings?

  • Generalized osteopenia
  • Widened growth plates
  • Bowing of weight bearing bones, ribs
  • Pseudofractures
  • Discontinuities due to buckling, tearing of bone
A

Rickets (a vitamin D deficiency) is

85
Q

What are the functional effects of rickets on lower extremities?

A
  • Hypotonia
  • Waddling gait
86
Q

Hypervitaminosis D is also known as…

A

vitamin D toxicity

87
Q

Excessive sensitivity to vitamin D can lead to what disease?

A

Sarcoidosis (collections of granulomas)

88
Q

What are the following clincal manifestations of?

  • Hypercalcemia
  • Increased urinary calcium excretion
  • Nephrolithiasis
  • Nephrocalcinosis
  • Metastatic calcifications
A

Hypervitaminosis D

89
Q

How does calcium affect the nervous system with hypercalcemia?

A

Calcium is a nervous system depressant

90
Q

Given that calcium is a nervous system depressant, what are some symptoms of hypercalcemia?

A
  • Dulled mentation
  • Headaches
  • Muscle weakness
  • Hyporeflexia
  • Lethargy
  • Anorexia
  • Constipation
  • Generalized musculoskeletal pain
91
Q

Hypervitaminosis D will have lab results of increased ___ and decreased ___

A

increased serum and urinary calcium levels and decreased PTH

92
Q

What is a treatment for hypervitaminosis D?

A

Stop vitamin D and calcium supplementation and wait

93
Q

Hypovitaminosis C is also known as…

A

scurvy

94
Q

Vitamin C is an important cofactor in the hydroxylation of ___ and ___

A

prolyl and lysyl residues in collagen

95
Q

What is the stabilizing helical structure of collagen?

A

Hydroxyproline and hydroxylysine

96
Q

What are the cross-linking tropocollagen fibers that create optimal molecular structure for collagen?

A

Hydroxyproline and hydroxylysine

97
Q

Collagen lacks ___ strength

A

tensile strength

98
Q

Historically, who was exceptionally vulnerable to scurvy?

A

Sailors

99
Q

What modern populations would be most at risk for scurvy?

A

People prone to malnutrition; babies, children, and older people

100
Q

The following are clinical manifestations of what disease?

  • Vessel fragility and increased hemorrhage
  • Subperiosteal bleeding
  • Petechial hemorrhages, ecchymoses and purpura after mild trauma
  • Swollen bleeding gums; alveolar resorption and tooth loss
A

Scurvy (hypovitaminosis C)

101
Q

The following are clinical manifestations of what disease?

  • Impaired bone growth
  • Joint and muscle pain
  • Delayed or impaired wound healing
A

Scurvy (hypovitaminosis C)

102
Q

The following are radiographic findings in what disease?

  • Generalized osteopenia
  • White line of Frankel
  • Wimberger’s ring
A

Scurvy (hypovitaminosis C)

103
Q

The following are radiographic findings in what disease?

  • Pelkin’s spurs
  • Trummerfeld zone
  • Subperiosteal hemorrhage
A

Scurvy (hypovitaminosis C)

104
Q

What is the effect of estrogen on osteoclast activity?

A

Inhibits osteoclast activity during bone remodeling

105
Q

Hypervitaminosis D is primarily a result of…

A

over supplementation

Musculoskeletal Physiopathology (13 decks)

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