Osteoporosis

Question 1

What are the different types of bone cells?

Answer 1

osteoclasts
osteoblasts
osteocytes
osteogenic cells

Question 2

What is the function of osteocytes?

Answer 2

maintain mineral concentration of matrix

Question 3

What is the function of osteoblasts?

Answer 3

bone formation

Question 4

What is the function of osteoclasts?

Answer 4

bone resorption

Question 5

What is the function of osteogenic cells?

Answer 5

develop into osteoblasts

Question 6

Describe normal adult bone.

Answer 6

composed of concentric rings of osteocytes with their dark nuclei in lacunae and thin processes called canaliculi
each osteon has a central haversian canal with vascular supply that reaches osteocytes via canaliculi
as the bone remodels over time, osteons appear with variable size and orientation
most of the bone is composed of hydroxyapatite crystal
-hydrated calcium phosphate
bony lamellae appear as white lines, arranged in parallel
cellular marrow present between the trabeculae
osteocytes lie in small lacunae connected by canals

Question 7

What controls the metabolism of bone?

Answer 7

serum calcium
vitamin D
PTH

Question 8

What does trabeculae form?

Answer 8

complex three-dimensional structure that provides strength without the weight of solid bone

Question 9

What occurs to bone with age?

Answer 9

imbalance in bone remodeling phases is observed with an increased bone resorption and a decrease in bone formation
leads to trabecular and cortical alterations:
-reduction in trabecular number
-decreased trabecular thickness
-increased trabecular spacing
-cortical thinning
-expansion of bone marrow cavity
INCREASED RISK OF FRACTURES

Question 10

What is osteoporosis?

Answer 10

multifactorial disease characterized by absolute reduction of total bone mass
-bone density is significantly reduced

Question 11

What percentage of hip fractures are caused by osteoporosis?

Answer 11

70-90%

Question 12

What is the standard criterion for the diagnosis of osteoporosis in postmenopausal women and older men?

Answer 12

T-score of < -2.5 at the lumbar spine, femur neck, or total hip by bone mineral density testing

Question 13

What is the T score of osteopenia?

Answer 13

T score -1 to -2.5

Question 14

What are the risk factors for primary osteoporosis?

Answer 14

low initial bone mass (small frame)
ethnicity
bad dietary habits, smoking
hormones
age-related changes in metabolism

Question 15

What are the two groups of osteoporosis?

Answer 15

primary: cause unknown; most common
secondary: related to another disease affecting otherwise normal bone; rare

Question 16

What are the many causes of secondary osteoporosis?

Answer 16

autoimmune: inflammatory factors affecting bone
-RA, lupus, MS, ankylosing spondylitis
digestive and GI disorders: decreased nutrient absorption
-Celiac, IBD, weight loss surgery
medical procedures:
-gastrectomy, GI bypass
cancer: invades bone
-breast or prostate
hematologic/blood disorders: blood cancers
-leukemia, lymphoma, sickle cell
neurologic disorders: mobility change affects turnover
-stroke, Parkinsons, MS, spinal cord injury
blood and marrow disorders:
-thalassemia
mental illness: nutrition/activity
-depression, eating disorders
endocrine/hormonal disorders:
-diabetes, hyperthyroid, Cushing, premature menopause
other diseases and conditions:
-AIDS, COPD, female athlete triad, CKD

Question 17

What is the female athlete triad?

Answer 17

loss of menstrual periods, eating disorder, and excessive exercise

Question 18

What is the pathogenesis of osteoporosis?

Answer 18

more bone cells being resorbed than being deposited
this imbalance results in progressive loss of bone density and a thinning of bone tissue
osteoporotic bones are more porous=vulnerable to fracture

Question 19

What are the consequences of osteoporosis?

Answer 19

compression fractures
radial fractures
break then fall
loss of height
stooped posture

Question 20

How do bisphosphonates work?

Answer 20

bind to bone
slow down the bone resorbing action of osteoclasts and promote osteoclast apoptosis

Question 21

What are the bisphosphonates used in Canada?

Answer 21

alendronate
etidronate
risedronate
zoledronic acid

Question 22

What are the adverse effects of bisphosphonates?

Answer 22

esophageal irritation (stay upright after administration)
osteonecrosis of the jaw

Question 23

How does denosumab work?

Answer 23

human monoclonal antibody that prevents RANKL-RANK interaction and thereby inhibits osteoclast formation
-Brand name: Prolia
-injected SQ q6mo

Question 24

What is the role of hormone therapy in osteoporosis?

Answer 24

estrogen +/- progesterone to increase density
SERMs: non-hormonal but act like estrogen
-Raloxifene

Question 25

What is the effect of estrogen on osteocytes?

Answer 25

decreased apoptosis
=decreased activation of bone remodeling

Question 26

What is the effect of estrogen on osteoblasts?

Answer 26

decreased apoptosis
decreased oxidative stress
decreased NF-kB activity
=maintenance of bone formation

Question 27

What is the effect of estrogen, T cells, and osteoblasts on osteoclasts?

Answer 27

increased apoptosis
decreased RANKL-induced differentiation
=decreased bone resorption

Question 28

What is the role of calcitonin? Is it effective in the treatment of osteoporosis?

Answer 28

inhibits bone resorption by osteoclasts and promotes bone formation by osteoblasts
not very effective, used when other treatments not tolerated

Question 29

What is the role of PTH? What is its role in therapy of osteoporosis?

Answer 29

activates osteoblasts
Teriparatide injection SQ daily, up to 2 yrs
-severe osteoporosis
-short term PTH has anabolic effect on bone by acting on
osteoblasts
-used with zoledronic acid

Question 30

What is sclerostin?

Answer 30

secreted by osteoblasts and inhibits maturation of osteoblasts
may be elevated in some inflammatory conditions

Question 31

What is the name of the sclerostin inhibitor?

Answer 31

romosumab