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Flashcards in Metabolic Bone Disease Deck (46):
1

How is bone formed?

- 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).

2

What are the 2 types of bone?

1. CORTICAL= mechanical and protective function.
- TRABECULAR= metabolic function.

3

What is the metabolic function of trabecular bone?

- to reserve ions (especially calcium and phosphate).

4

What is the macroscopic organization of bone?

- cortex= compact (cortical) bone (80-90% calcified).
- trabecular= cancellous (spongy) makes up the remainder.

5

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

- more (80%) compared to cortical bone's 20%, except in women after menopause.

6

What are the biochemical markers of bone formation?

- serum osteocalcin
- serum alk phos
- serum procollagen I extension peptides.

7

What are the biochemical markers of bone resorption?

- urinary N-telopeptide collagen crosslinks
- urinary deoxypyridinoline

8

What is the gold standard test for measuring osteoporosis?

- DEXA scan of vertebral spine or femoral neck

9

What is Osteomalacia?

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

10

What can cause of osteomalacia?

- vitamin D deficiency (most common)
- renal phosphate loss
- failure of intestinal absorption of calcium, phosphate or vitamin D.

11

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

- bowing of long bones
- widening of the epiphyses
- bone pain, tenderness, and muscle weakness.

12

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

- hypoplastic teeth
- caries producing pulpitis
- abscesses

13

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

- 1, 25-dihydroxy D3

14

To what type of fracture does osteoporosis lead most often?

- hip fractures
*be aware in post menopausal women.

15

Does osteoporosis cause more loss of trabecular or cortical bone?

- more trabecular, but also cortical.

16

What is Osteoporosis?

- reduction in TRABECULAR bone mass, resulting in porous bone with an increased risk for fracture.

17

What are the 2 major causes of bone loss?

1. age
2. estrogen deficiency (don't forget younger women with hysterectomy).

18

What demographic is most at risk for osteoporosis?

- Caucasian women or Asian.
- short stature, slender build, small bones.
- Family Hx
- smoking hx
- estrogen deficiency

19

Can certain disease or drugs cause osteoporosis?

- YES (corticosteroids, alcohol, heparin, thyroxine, cyclosporine...)

20

What is the most common type of metabolic bone disease?

- Osteoporosis

21

When do you reach your peak bone mass?

- age 30

22

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

- osteoPENIA

23

What type of exercise must pts with osteoporosis do?

- WEIGHT BEARING exercise

24

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

- within 5 years of menopause

25

How will pts with an osteoporosis fracture present grossly?

- kyphosis of the thoracic spine
- height loss
- wedge deformity on x-ray

26

What are the 2 types of osteoporosis?

1. postmenopausal (type 1)
2. senile (type 2)= old or aged

27

How does the DEXA scan measure bone density?

- 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

** What is the T-score?

- standard deviations above or below the mean of YOUNG ADULTS.
*the T-score is KEY.

29

** What is the Z-score?

- standard deviations above or below the mean age, gender, and race matched individuals.

30

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

- 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

** What is the WHO definition of osteoPENIA?

- bone mineral density is 1 to 2.5 standard deviations below peak bone mass.

32

** What is the WHO definition of osteoPOROSIS?

- 2.5 standard deviations below peak bone mass.

33

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

- bone density plus age, previous fracture, family hx of osteoporosis, steroid use, and smoking.

34

How do we prevent osteoporosis?

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

35

What drugs do we use for osteoporotic fracture prevention?

- HRT (controversial)
- raloxifene
- bisphosphonates (alendronate, risedronate)
- calcitonin
- PTH
- denosumab
- reclast (annually)

36

What are the potential risks of HRT?

- breast cancer?
- DVT and PE
- breast tenderness
- endometrial cancer with intact uterus (if unopposed)
- weight gain

37

What are some alternatives to HRT for osteoporosis?

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

38

How do the bisphosphonates work?

- interfere with cell signaling mechanisms to reduce the resorptive actions of mature osteoCLASTS.

39

What are some risks of bisphosphonates?

- osteonecrosis of the jaw
- atraumatic long bone fractures
- carcinoma of the esophagus

40

What is Denosumab? (DRUG OF CHOIC)

- monoclonal antibody directed against RANKL in osteoBLASTS, thus PREVENTING activation of osteoCLASTS.
*injection given every 6 months.

41

What are the side effects of denosumab?

- hypocalcemia
- increased risk of serious infections
- rashes
- osteonecrosis of the jaw

42

*** What is associated with PRIMARY hyperparathyroidism?

- MEN 1= 95% hyperplasia + pancreatic and pituitary tumors.
- MEN 2A= 50% hyperplasia + medullary thyroid cancer and pheochromocytoma.

43

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

- 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

What is most associated with secondary hyperparathyroidism?

- chronic kidney disease, causing increased phosphorous and decreased calcium, worsening hyperparathyroidism.

45

Is vitamin D3 or D2 better for supplementation?

- D3 at least 800 IU

46

What are the clinical manifestations of hyperparathyroidism?

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