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Endocrinology > Metabolic Bone Disease > Flashcards

Metabolic Bone Disease Flashcards

1
Q

How is bone formed?

A
  • osteocytes (bone cells) are embedded in an organic matrix of collagen fibers and noncollagenous protein.
  • binding of calcium phosphate in the form of hydroxyapatite crystals.
  • constantly renewed (resorption and replacement).
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2
Q

What are the 2 types of bone?

A
  1. CORTICAL= mechanical and protective function.

- TRABECULAR= metabolic function.

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3
Q

What is the metabolic function of trabecular bone?

A
  • to reserve ions (especially calcium and phosphate).
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4
Q

What is the macroscopic organization of bone?

A
  • cortex= compact (cortical) bone (80-90% calcified).

- trabecular= cancellous (spongy) makes up the remainder.

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5
Q

Does trabecular (cancellous/spongy) bone remodel more or less than cortical bone?

A
  • more (80%) compared to cortical bone’s 20%, except in women after menopause.
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6
Q

What are the biochemical markers of bone formation?

A
  • serum osteocalcin
  • serum alk phos
  • serum procollagen I extension peptides.
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7
Q

What are the biochemical markers of bone resorption?

A
  • urinary N-telopeptide collagen crosslinks

- urinary deoxypyridinoline

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8
Q

What is the gold standard test for measuring osteoporosis?

A
  • DEXA scan of vertebral spine or femoral neck
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9
Q

What is Osteomalacia?

A
  • inadequate mineralization of bone matrix, due to low calcium-phosphate product (hypocalcemia, hypophosphatemia or both).
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10
Q

What can cause of osteomalacia?

A
  • vitamin D deficiency (most common)
  • renal phosphate loss
  • failure of intestinal absorption of calcium, phosphate or vitamin D.
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11
Q

What will you see in Osteomalacia (adults)/Rickets (children)?

A
  • bowing of long bones
  • widening of the epiphyses
  • bone pain, tenderness, and muscle weakness.
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12
Q

What will teeth look like in vitamin-D resistant Rickets?

A
  • hypoplastic teeth
  • caries producing pulpitis
  • abscesses
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13
Q

If a pt has Rickets due to lack of 1-hydroxylase in the kidney, how do you treat?

A
  • 1, 25-dihydroxy D3
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14
Q

To what type of fracture does osteoporosis lead most often?

A
  • hip fractures

* be aware in post menopausal women.

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15
Q

Does osteoporosis cause more loss of trabecular or cortical bone?

A
  • more trabecular, but also cortical.
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16
Q

What is Osteoporosis?

A
  • reduction in TRABECULAR bone mass, resulting in porous bone with an increased risk for fracture.
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17
Q

What are the 2 major causes of bone loss?

A
  1. age

2. estrogen deficiency (don’t forget younger women with hysterectomy).

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18
Q

What demographic is most at risk for osteoporosis?

A
  • Caucasian women or Asian.
  • short stature, slender build, small bones.
  • Family Hx
  • smoking hx
  • estrogen deficiency
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19
Q

Can certain disease or drugs cause osteoporosis?

A
  • YES (corticosteroids, alcohol, heparin, thyroxine, cyclosporine…)
20
Q

What is the most common type of metabolic bone disease?

A
  • Osteoporosis
21
Q

When do you reach your peak bone mass?

A
  • age 30
22
Q

What does 1 standard deviation below normal indicate on a DEXA scan?

A
  • osteoPENIA
23
Q

What type of exercise must pts with osteoporosis do?

A
  • WEIGHT BEARING exercise
24
Q

In what stage of a woman’s life can she lose 1/3 of her bone mass?

A
  • within 5 years of menopause
25
Q

How will pts with an osteoporosis fracture present grossly?

A
  • kyphosis of the thoracic spine
  • height loss
  • wedge deformity on x-ray
26
Q

What are the 2 types of osteoporosis?

A
  1. postmenopausal (type 1)

2. senile (type 2)= old or aged

27
Q

How does the DEXA scan measure bone density?

A
  • abosolute value (g/cm2) for patient
  • comparison to sex and age-matched reference values (Z-score).
  • comparison to premonopausal mean peak reference values (T-score or young adult Z-score).
28
Q

** What is the T-score?

A
  • standard deviations above or below the mean of YOUNG ADULTS.
  • the T-score is KEY.
29
Q

** What is the Z-score?

A
  • standard deviations above or below the mean age, gender, and race matched individuals.
30
Q

** What are the T-SCORE criteria for assessing disease severity of osteoporosis? (TEST QUESTION)

A
  • normal= greater or equal to -1.0
  • osteopenia (low bone mass)= between -1.0 to -2.5
  • osteoporosis= less or equal to -2.5
  • severe osteoporosis= less than -2.5 with fracture.
31
Q

** What is the WHO definition of osteoPENIA?

A
  • bone mineral density is 1 to 2.5 standard deviations below peak bone mass.
32
Q

** What is the WHO definition of osteoPOROSIS?

A
  • 2.5 standard deviations below peak bone mass.
33
Q

*** What does the new risk assessment of osteoporosis (FRAX) include?

A
  • bone density plus age, previous fracture, family hx of osteoporosis, steroid use, and smoking.
34
Q

How do we prevent osteoporosis?

A
  • appropriate calcium and vitamin D intake in diet.
  • lifestyle= weight bearing exercise
  • HRT beginning in perimenopause
  • analgesics for pain as needed.
35
Q

What drugs do we use for osteoporotic fracture prevention?

A
  • HRT (controversial)
  • raloxifene
  • bisphosphonates (alendronate, risedronate)
  • calcitonin
  • PTH
  • denosumab
  • reclast (annually)
36
Q

What are the potential risks of HRT?

A
  • breast cancer?
  • DVT and PE
  • breast tenderness
  • endometrial cancer with intact uterus (if unopposed)
  • weight gain
37
Q

What are some alternatives to HRT for osteoporosis?

A
  • mixed estrogen agonist/antagonist

- SERM (selective estrogen receptor modulators)= tamoxifen (1st gen) or raloxifene (2nd gen).

38
Q

How do the bisphosphonates work?

A
  • interfere with cell signaling mechanisms to reduce the resorptive actions of mature osteoCLASTS.
39
Q

What are some risks of bisphosphonates?

A
  • osteonecrosis of the jaw
  • atraumatic long bone fractures
  • carcinoma of the esophagus
40
Q

What is Denosumab? (DRUG OF CHOIC)

A
  • monoclonal antibody directed against RANKL in osteoBLASTS, thus PREVENTING activation of osteoCLASTS.
  • injection given every 6 months.
41
Q

What are the side effects of denosumab?

A
  • hypocalcemia
  • increased risk of serious infections
  • rashes
  • osteonecrosis of the jaw
42
Q

*** What is associated with PRIMARY hyperparathyroidism?

A
  • MEN 1= 95% hyperplasia + pancreatic and pituitary tumors.

- MEN 2A= 50% hyperplasia + medullary thyroid cancer and pheochromocytoma.

43
Q

*** What labs will you see with primary hyperparathyroidism?

A
  • high serum calcium and chloride
  • high serum PTH and alk phos
  • low serum phosphorous and HCO3-
  • high urine calcium
  • high urine phosphorous
  • high urine cAMP
44
Q

What is most associated with secondary hyperparathyroidism?

A
  • chronic kidney disease, causing increased phosphorous and decreased calcium, worsening hyperparathyroidism.
45
Q

Is vitamin D3 or D2 better for supplementation?

A
  • D3 at least 800 IU
46
Q

What are the clinical manifestations of hyperparathyroidism?

A
  • usually asymptomatic.
  • may see vertebral compression fractures with minimal stress (sneezing, bending).
  • back pain that radiates laterally.
  • dorsal kyphosis/cervical lordi

Endocrinology (18 decks)

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