Quiz 3: Bones Flashcards Preview

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Flashcards in Quiz 3: Bones Deck (17):
1

Terminology: Formation, Breakdown, Remodeling/Turnover

Osteogenesis: new bone formation
Resorption: absorption of old bone
Remodeling or Turnover: Reshaping –Depositing (formation) and absorbing (breakdown) bone to make new bone

2

Regulation of Ca, PO4 and Bone Metabolism

Three Hormones:
Parathyroid Hormone (PTH)
Vitamin D
Calcitonin

3

Bone Types

Cortical: primary type in long bones, Strong and rigid
Trabecular: primary type in axial skeleton like the vertebrae, Numerous cross-hairs, Strength and elasticity
Mixtures of the two: Femoral neck, Distal radius

4

Bone Assays

Calcium
Phosphate
Magnesium
Alkaline Phosphatase
PTH
Vitamin D
Calcitonin
Bone Markers

5

Bone Composition

- Mineral: Ca & PO4 in hydroxyapatite crystals
- Collagen fibers-- 25% hydroxyproline or proline
- Cells:
+ Osteoblasts: make new bone matrix
+ Osteocytes: regulatory functions
+ Osteoclasts: phagocytic cells that respond to PTH for resorption: contain enzymes to demineralize & digest bone

6

Bone Turnover Markers

Identify and Monitor Patients at Risk for significant bone loss
Monitor compliance of therapy
Monitor Progress of Anti-resorptive treatment (before bone density improves): Faster than bone scan, compliance, adjust medication levels

7

Patients at risk for bone loss

Post-menopausal women
Metabolic bone diseases
Renal diseases
Malnutrition
Chronic alcoholism
Low physical activity & immobility
Medications
Premenopausal amenorrhea
Hypogonadism
GNRH therapy (endometriosis)
Thyrotoxicosis
Hyperparathyroidism
VitaminD deficiency

8

2 Main Bone Markers

1. Resorption: C-Telopeptide (CTx)
2. Formation: Type 1 Procollagen C terminal Propeptide (P1CP)

9

Osteocalcin

1% of total protein in bone.
Synthesized by osteoblasts (cells that form bone)
Plasma levels reflect osteoblast activity

10

Osteocalcin Measurement and Levels

Immunoassay
Serum = male 3 - 13 ng/mL
female premenopausal 0.4 - 8.2 ng/mL, postmenopausal 1.5 - 11.0 ng/mL
Levels reflect bone formation

11

Osteoporosis

Primary: postmenopausal
Secondary : malnutrition, drugs, alcoholism, or metabolic disease
44 Million Americans at risk
Female: Male 4: 1
1.5 Million Fracture/year in US ($19 billion): Vertebral Compressions, Hip, Distal Forearm
40-50% lifetime risk for Caucasian Women

12

Osteomalacia (rickets in children)

Rickets: Children: Low Vitamin D
Adults: low Vit D, Ca, PO4, Impaired mineralization

13

Osteitis Fibrosa

Hyperparathyroidism (PTH elevated)
Renal failure

14

Osteoporosis Treatment

Treat Fracture
Modify preventable Risk factors: smoking, alcohol, risk of falls, walkers, bedrails, etc
Add dietary Ca and Vitamin D
Prevention for family members: Exercise, diet
Medications

15

Osteoporosis Medication

Slow Bone Loss (Reduces resorption): Bisphosphonates.
SERMS: selective estrogen receptor modulators
Hormones: Calcitonin, Estrogen
Bone Formation and Reduces resorption
Teriparatide (Forteo). This powerful drug, an analog of parathyroid hormone. It works by stimulating new bone growth

16

Paget's Disease

- Aggressive osteoclast-mediated bone resorption preceding imperfect osteoblast-mediated bone repair.
- Thickening and hypertrophy of long bones and deformity of flat bones
- Presents with bone softening, pain, fractures, bone deformity
- Detected by radiography and very elevated serum ALP. Ca usually normal.

17

Paget's Disease Treatment

Pharmacological treatment includes bisphosphonates (bind to and inhibit calcium) and calcitonin.
Additional drugs as required for pain and inflammation.