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Metabolic Bone Disease
Dewhan Lecture
17
Pathology
Professional
01/18/2011

Additional Pathology Flashcards

 


 

Cards

Term




Osteoporosis

Definition

- bone disease characterized by compromised bone strength predisposing to an increased risk of fracture.

 

Bone strength is determined by bone density (peak bone mass and amount of bone loss) and bone quality (architecture, turnover, damage and mineralization).


Because we do not have an easy way to test bone strength, we test bone mineral density as a surrogate method.

Term




Osteopenia And Osteomalacia

Definition

Osteopenia- low bone density/mass (matrix) manifested as   radiolucency of bone.

 

Osteomalacia- progressive loss of calcium and phosphorus from bones with normal bone matrix resulting in increased bone fragility and risk of fracture.

Term




Epidemiology

Definition

Post menopausal osteoporosis affects:

4 – 6 million postmenopausal white women.

13 – 17 million more have hip osteopenia and are       at risk for hip fracture.

 

Primarily affects white and Asians, however a significant, but lower risk still exists for black women.

 

About half of white women over age 50 are expected

to fracture in their remaining lifetime.

Term




 

Mechanisms of Steroid Induced Osteoporosis

Definition

Bone loss occurs within the 6-12 months of start of drug 2o:

   ↑   osteoclast activity

    ↑  urinary Ca excretion

↓  osteoblast activity (shortened lifespan)

↓  GI Calcium absorption

 ↓ estrogen and testosterone levels  

Term




Bone Loss

Definition

Around age 30:
Formation unable to keep up with resorption
Resorption cavities are left unfilled
Resorption/Formation imbalance leads to bone loss

Term




Bone Remodeling

Definition

A – Osteoclastic bone resorption

B – Recruitment of Osteoblasts to form Matrix

C – Matrix mineralization to form sturdy bone

Term




Methods of evaluating BMD

Definition

-Radiographs

 

-Single photon absorptiometry-  radius or heel

 

-Quantitative Cat Scan- lumbar spine

 

-Calcaneal ultrasound

 

-Dual Energy X-ray Absorptiometry (DXA)- gold standard low radiation exposure and takes 20 minutes

Term




DXA Interpretation

 

Definition

Z-score defines how the bone mineral density (BMD) compares   to age matched controls. 

 

 

A z-score of < -2.0 is interpreted as “below the   expected range for age”.

 

A z-score of > -2.0 is interpreted as “within the   expected range for age”.


As a result, the only reason to order a DXA in premenopausal   women and men < 50 years old, is either to establish a   baseline BMD prior to treatment or to assess their   response to therapy.


At least 2 different locations must be tested:

  spine (2 consecutive vertebral bodies)

  right hip (total hip or femoral neck or trochanter)

  left hip (total hip or femoral neck or trochanter)

  nondominant midshaft radius (known as 33%   (esp. if a cortical bone disorder such as   hyperparathyroidism)

Lowest T score defines the condition.

 

 

Term




General approach to treating the

 

Osteoporotic patient

Definition

1.  Risk profile modification- such as tobacco and ETOH

 

2.  Fall risk assessment

 

3.  Weight bearing physical activity-

  improve muscle strength, mobility,

  functional status and stabilize bone mass

 

4.  Assure adequate Calcium and Vitamin D intake

Term




When to Treat with Medications

Definition

T score < -2.5

 

T score < -1.5 with risk factors for low bone mass


 

Prior fragility (low trauma) fracture

Term




Selective Estrogen Receptor Modulators (SERMs) Advantages/Disadvantages

 

Definition

Potential Advantages

May reduce cholesterol

 

May protect bone

May reduce breast CA

May reduce uterine CA

May maintain pelvic muscles

May reduce Alzheimer’s disease

 

Potential Disadvantages

May exacerbate hot flushes

May increase DVT
(esp. if bedridden)

 

 

Term




Calcitonin

Definition

Only used for Osteoporosis treatment not prevention

 

Special value because of analgesic effects in patients with back pain from acute fracture

 

 Side effects:

  nasal dryness, rhinitis and allergy to salmon calcitonin

Term




                      Bisphosphonates

Definition

Alendronate (Fosamax) Ibandronate (Boniva) Risedronate (Actonel)

Zoledronic Acid (Reclast)

 

Poorly absorbed from GI tract:

  

1.  Must be taken on empty stomach with 6-8 oz H2O,

  

2.  30 minutes before consuming anything and

  

3.  Must remain upright for at least 30 minutes to

  decrease risk of esophagitis.


Weekly, monthly and yearly dosing improves patient compliance.

 

Avoid in patients with significant GERD (reflux disease) or renal   dysfunction.

 

? Osteonecrosis of the jaw.

Term




Estrogen Replacement Therapy Pros

Definition

PROS

 

  Decreases rate of bone loss after menopause

 

  Maintains/increases BMD

 

  Relieves postmenopausal symptoms

 

  May prevent Alzheimer’s disease

Term




Estrogen Replacement Therapy Cons

Definition

  CONS


Troublesome side effects:

 

irregular bleeding,

 

fluid retention,

             

mastalgia,

 

headache,

 

mood swings  


Possible increased risk of breast cancer with long-term use

 

Must be taken with progestin to avoid risk of endometrial   hyperplasia/cancer

 

Deep venous thrombosis (may be eliminated by  transdermal estradiol)

 

Favorable effects on lipoprotein profile; but does not   appear to protect against CVD

Term




Osteomalacia and Rickets

Definition

Presentation: nonspecific or vague bone pain, may be malnourished
Imaging Studies: radiographs show widened physis
Looser’s transformation zones also known as pseudofractures are lines of radiolucency that represent stress fractures with unmineralized osteoid
Laboratory Studies: low or normal serum calcium, phosphorus or vitamin D, increased alkaline phosphatase

Definitive diagnosis by bone biopsy

Term




Paget’s Disease

Definition

Osteitis Deformans is a condition of abnormally increased and disorganized bone remodeling
Not systemic, but within bones
Viral infection of osteoclasts in genetic susceptible individuals may be cause
Rapid resorption-rapid bone formation leads to mosaic of disorganized immature (woven) bone
May be painful, malignant, may fracture
Femur, tibia, pelvis and skull

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