Bone Physiology

Question 1

hypocalcemia

Answer 1

hyperexcitablity

Question 2

hypercalcemia

Answer 2

depressed activity

Question 3

what triggers as result of low calcium

Answer 3

PTH secretion

Question 4

four functions of PTH

Answer 4

• increased bone resorption
• increased kidney reabsorption
• block phosphate reabsorption
• stimulate conversion 25OH VitD to 1,25OH VitD

Question 5

why is P excretion help with Ca absorption

Answer 5

if their levels rise together
-they will precipitate out

if want calcium up we need P down

Question 6

role of 1,25OH VitD

Answer 6

• calcium reabsorption of gut
• stimulate P reabsorption
• allows mineralzation
• shuts off its own synthesis (negative feedback)

Question 7

what happens in a loop

Answer 7

absorption and mineralization

Question 8

where is 25OH Vit D converted to 1,25OH Vit D

Answer 8

kidney

Question 9

insufficient 1,25 Vit D levels lead to what?

Answer 9

poor mineralization and impaired calcium absorption

Question 10

calcitriol

Answer 10

1,25OH VitD

Question 11

calcitonin

Answer 11

tumor marker

Question 12

FGF23 absence?

Answer 12

hyper-P and hyper-Ca

Question 13

markers for bone formation

Answer 13

alkaline phosphatase
osteocalcin
procollagen peptides (PINP/PICP)

Question 14

markers of bone resorption

Answer 14

urinary hydroxyproline
NTX/CTX or N-telopeptides/C-telopeptides
pryidinoline
deoxypyridinoline

Question 15

scurvy

Answer 15

Vit C deficinency (ascorbic acid)

• cannot crosslink collagen
• fragile bones

Question 16

bone growth during childhood

Answer 16

growth of cartilage > endochondral bone formation

Question 17

increase in bone width?

Answer 17

periosteal apposition

Question 18

bone modeling

Answer 18

net bone formation

-two processes uncoupled

Question 19

remodeling

Answer 19

coupled process where resorption followed by bone formation

no net gain in bone

Question 20

osteoblast activity

Answer 20

lay down collagen and noncollagen proteins

Question 21

mineralization of bone?

Answer 21

delayed a few days to allow cross linking

Question 22

released by osteoblasts during bone formation?

Answer 22

osteocalcin and alkaline phosphatase

Question 23

signal for osteoclast activity?

Answer 23

PTH > osteoblasts > activate osteoclasts

Question 24

calcitonin receptor?

Answer 24

inhibitory for osteoclasts

Question 25

PTH on osteoblasts?

Answer 25

causes release of M-CSF | -differentiation to osteoclast progenitors of hematopoietic stem cells

Question 26

osteoblast affect on osteoclasts?

Answer 26

RANK-L by osteoblasts binds RANK on osteoclasts - triggers activity

Question 27

OPG

Answer 27

osteoprotegerin -inhibits bone resorption of osteoclast soluble receptor for RANK-L

Question 28

Vitamin D

Answer 28

necessary for mineralzation of bone

Question 29

PTH

Answer 29

signals osteoblasts to activate osteoclasts (resorption)

Question 30

calcitonin

Answer 30

inhibits bone resorption (osteoclasts)

Question 31

hormones increasing bone formation?

Answer 31

growth hormone thyroid hormone insulin gonadal hormones

Question 32

hormones increasing bone resorption?

Answer 32

glucocorticoids - suppress GI absorption - induce osteoclastogenesis - deplete osteoblasts

Question 33

prostaglandins

Answer 33

stimulate bone resorption

Question 34

DEXA scan and T scores?

Answer 34

can measure bone density >-1 normal -1 to -2.5 osteopenia <-2.5 osteoporosis

Question 35

bone biopsy

Answer 35

give architectural structure

Question 36

risk factors for osteoporosis? - modifiable - nonmodifiable

Answer 36

modifiable - age - race - gender - menopause - build - family Hx nonmodifiable - Ca intake - Vit D intake - estrogen deficiency - sedentary - smoking - alcohol - caffeine - meds

Question 37

two drugs for osteoporosis?

Answer 37

antiresorptive and anabolic

Question 38

antiresorptive drugs?

Answer 38

bisphosphonates

Question 39

anabolic drugs?

Answer 39

intermittent PTH

Question 40

osteomalacia

Answer 40

aka rickets disorders in mineralization -deficiency in Vit D

Question 41

Pagets disease

Answer 41

excessive osteoblast activity | -treatment - bisphosphonates

Question 42

extremely elevated alkaline phosphatase?

Answer 42

sclerotic phase of pagets

Question 43

osteogenesis imperfecta

Answer 43

brittle bone disease weakening of bone due to mutations in collagen leading to fractures and deformity

Question 44

OI type I

Answer 44

most common autosomal dominant -one allele of alpha-1 procollagen is missing

Question 45

OI type II

Answer 45

more rare point mutation of COL1A1 -extreme bone fragility and death

Question 46

osteopetrosis

Answer 46

marble bone disease defective osteoclastic resorption

Question 47

prolia

Answer 47

denosumab monoclonal antibody for RANK-L blocks bone resorption

Question 48

benefit to combining antiresorptive and anabolic?

Answer 48

no

Question 49

how to inhibit bone formation?

Answer 49

inhibit bone resorption by using bisphosphonates