Metabolic Bone Disease Flashcards
Bone remodeling
- osteoclasts: make resorption pits using enz/acid
- osteoblasts: fill pit back up with osteoid (bone specific collagen, high affinity for Ca phosphate crystal): calcifying osteoid: Ca x PO4 greater than 24
Osteoclasts have RANK, which binds RANK-L
lots of RANK L and not much OPG: bone resorption high (high OPG bone resorption low)
Sclerostin
prevents new bone formations
Promotion of osteoblasts (signaling)
Wnt
Frizzled/LRP5
B-catening
Osteoporosis
compromised bone strength, increased risk of fragility fractures
Types of fragility fractures and RFs
spine, most (only 1/3 cause pain)
hip
wrist
fragility fractures= osteoporosis
RFs: age falls low bone mass previous fractures
T score
SDs below peak bone mass
- 1-2.5 below peak bone mass: osteopenia
- 2.5 and further below: osteoporosis
abnormal bone remodeling
increased resorption or decreased formation: bone mass lost
Non modifiable RFs fro low bone mass
Age Race Gender Family History Early Menopause
Modifiable
Low Calcium Intake Low Vitamin D Intake Estrogen Deficiency Sedentary Lifestyle Cigarette Smoking Excess Alcohol (greater than 2/day) Excess Caffeine (greater than 2/day) Medications: Glucocorticoids, Excess Thyroid Hormone, Anticonvulsants Probable/Possible: Thiazolidinediones, SGLT2-I’s, SSRI’s, PPI’s
Osteoporosis Prevention and Tx
1000-1500 mg Ca/d
Vit D: 1000units/d
exercise: aerobic, resistance
falls: assess/prevent
Osteomalacia and rickets
impaired bone mineralization resulting in soft, weak bones
Osteomalacia: adults
rickets: kids
*inadequate ca x phosphate product for bone mineralization (should be above 24)
Phosphate disorders
Acquired Hypophosphatemia
Poor Oral Intake
Renal Phosphate Wasting
Congenital Hypophosphatemic Rickets
“Vitamin D Resistant Rickets”
Renal Phosphate Wasting
Impaired 1,25 (OH)2 Vitamin D Formation
Osteomalacia features, and readiology
pain
deformities
fractures
Radiology:
fractures
pseudofractures (Milkman’s Fractures; Looser’s Lines)
Rickets features and radiology
pain
deformities
muscle weakness
short stature
Radiology
bowing of long bones
flaring ends of long bones
-delayed epiphyseal calcification
Paget’s Disease of Bone
-an idiopathic bone condition characterized by excessive/unregulated bone resorption and formation
- genetic (familial aggregation; 18q linkage; mutation of osteoprotegerin gene; mut of sequestosome 1/P62 gene)
- chronic paramyxovirus infection
- viral disorder evidence (geographic variation; dog ownership; time trends; viral studies)