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GI Block > Endo: Metabolic Bone Dz > Flashcards

Endo: Metabolic Bone Dz Flashcards

1
Q

What is the function of osteoclasts?

What is the function of osteoblasts?

A
  • Osteoclasts degrade bone using acid and collegenases
  • Obsteoblasts lay down osteoid (unmineralized bone)
    • Catalyze calcification if there is sufficient calcium and phosphorus
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2
Q

What are osteocytes?

Name 3 functions

A
  • Terminally differentiated osteoblasts embedded in bone matrix
  • Have mechanoreceptors that sense stress on bones
  • Secrete sclerostin and FGF-23
  • Orchestrate bone remodeling process
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3
Q

Describe the role of RANK (3)

A
  • Osteocytes secrete RANK-Ligand
  • RANK-L bind to RANK on osteoclasts to activate them
  • Osteoprotegrin binds and sequesters RANK-Ligand (preventing activation of osteoclasts)
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4
Q
A
  • RANK-L stimulates osteoclasts
  • Wnt/B-catenin stimulate osteoblasts
  • Sclerostin inhibits WNT/B-catenin pathway
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5
Q

Describe 2 ways of measuring the result of a bone density (DXA) scan.

A
  • T-Score: Bone Mineral Density compared to young, healthy Caucasian woman at their peak BMD
  • Z-score: BMD compared to age & gender matched controls
    • Useful in younger men and pre-menopausal women
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6
Q

Define osteoporosis

A

Impaired bone strength that predisposes it to fractures

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7
Q

Name 3 ways to diagnose Osteoporosis

A
  1. DEXA T-score of -2.5 or lower
  2. Fragility fracture
  3. Greater than 20% Major Osteopathic Fracture risk or greater than 3% hip fracture risk
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8
Q

What demogrpahic is at highest risk for osteoporosis?

Why does low BMI increase osteoporosis risk?

A
  • Highest risk: Caucasian women with positive family history and early menopause
  • Low BMI (less than 20) increases risk b/c there is less weight-dependence during every day activities
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9
Q

What are the 2 components of bone strength?

A
  1. Bone density (assessed with DEXA)
  2. Bone quality
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10
Q

Name one drug that causes significant bone resportion

A

Glucocorticoids

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11
Q

What is the effect of estrogen on bones?

What effect does menopause have?

A
  • Estrogen promotes osteoblast survival and apoptosis of osteoclasts (promotes overall bone strength)
  • Menopause = estrogen deficiency, increases osteoporosis risk
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12
Q

What are two common Ca supplements?

Which is preferable?

A
  • Calcium carbonate
    • Highest calcium, so generally preferred
  • Calcium citrate
    • Used if low gastric acid production (using PPI, H2 blocker)
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13
Q

Define Osteomalacia and Rickets

A
  • Impaired mineralization of osteoid (due to inadequate calcium or phosphate)
  • Osteomalacia = adult version
  • Rickets = kids version
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14
Q

What is the most common cause of osteomalacia/rickets?

Mechanism?

A

Vitamin D disorders

Low Vitamin D -> low serum Ca -> increased PTH -> decreased phosphate

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15
Q

What would be the values of Ca, Phos, PTH, and ALP in osteomalacia and rickets?

A
  • Low Ca, low Phosphate
  • Elevated PTH
  • Elevated ALP
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16
Q

What cells release FGF-23?

What is the function of FGF-23?

A
  • FGF-23 released by osteocytes
  • It increases phosphate excretion in urine and decreases phosphate absorption in gut (overall decreases serum phosphate)
17
Q

Is osteomalacia/rickets painful?

Is osteoporosis?

A
  • Osteomalacia/rickets often is painful
  • Osteoporosis is not painful
18
Q

Deformities of rickets? (3)

A
  • Bowing of legs
  • Widened wrists
  • Rachitic rosary
19
Q

Define Paget’s disease of bone.

Where does it occur?

A
  • Idiopathic condition of excessive and unregulated bone remodeling
  • Disease process is localized to one or a few sites
20
Q

Characteristics of the bone in Paget’s disease (3)

A
  • Increased osteoclast number and activity
  • Disorganized woven and lamellar bone
  • Hypervascular
21
Q

Paget’s symptoms (4)

A
  • Pain
  • Deformity
  • Fractures
  • Osteoarthritis (secondary to altered gait)
22
Q

3 potential complications of Paget’s disease of bone

A
  • CN compression (especially CN 8, causing deafness) or spinal cord compression
  • High output HF due to atriovenous shunts
  • Increased risk of osteogenic sarcoma
23
Q

Describe the clinical course of Paget’s disease

A
  1. Only osteoclast activity
  2. both osteoclast and osteoblast activity
  3. ONLY osteoblast activity (sclerosis)
24
Q

X-Rays in Paget’s disease? (3)

Bone scan in Paget’s? (1)

A
  • X Ray
    • Osteolytic lesion
    • Osteosclerotic lesions nearby
    • Thickened cortex and trabecula
  • Bone scan
    • Focal area of intense uptake
25
Q

Paget’s disease treatment (2)

A
  • Zoledronate (IV)
  • Oral bisphosphonate
26
Q

What does elevated bone alk phos indicate?

A

Increased osteoblast activity

27
Q

What would the Ca, Phos, ALP, and PTH be in Paget’s disease?

A
  • ALP is elevated
  • All else is normal

GI Block (77 decks)

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