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Metabolic Bone Disease Flashcards

1
Q

What are the actions of parathyroid hormone?

A
  1. Bone: increase resorption by osteoclasts, releasing calcium
  2. Kidney: increases calcium resorption
  3. Vitamin D: activates so increase gut absorption
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2
Q

What senses calcium levels?

A

The parathyroid glands, chief cell calcium sensing receptor

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3
Q

What regulates the activity of 1alpha hydroxylase?

A
  1. High PTH
  2. Low PO4
  3. Concentration of calcium
  4. Amount vitamin D
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4
Q

What signalling pathway activates osteoclasts activity?

A

RANK activation

Turned on by PTH, vitamin D, cortisol, cytokines

Turned off by estrogen

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5
Q

How is bone remodelled?

A

Removal of existing bone by osteoclasts
Laying down of new matrix by osteoblasts
Mineralization

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6
Q

What factors influence new bone matrix formation?

A

Increase: mechanical loading, fractures

Decrease: glucocorticoids, malnutrition, immobilization

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7
Q

What influences speed of bone mineralization?

A

Increase: nucleation site, alkaline phosphatase enzyme presence

Decrease: acid, lack of minerals

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8
Q

How does hypocalcemia present?

A
  1. Neuromuscular excitability: tetany, seizures, perioral numbness
  2. LARYNGOSPASM!
  3. Chronically can present with cataracts, growth abnomalities
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9
Q

What are the two signs of hypocalcemia?

A
  1. Chvostek’s sign: facial nerve excitability

2. Trousseau’s sign: hand clench

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10
Q

What are the typical causes of hypoparathyriodism?

A
  1. Post thyroid/ neck surgery
  2. Autoimmune: addison’s
  3. Radiation
  4. Infiltrative disease
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11
Q

What causes severe hyperphosphatemia?

A
  1. Tumor lysis

2. Rhabdomyolysis

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12
Q

Paget’s Disease of the bone

A
  1. Uncontrolled activity of osteoclasts leads to chaotic formation of new bone
  2. Axial skeleton
  3. Sx: bony pain, joint arthritis, bony deformity, pathological fracture
  4. Ix= x ray
  5. Tx= bisphosphonates
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13
Q

Why does hyperphosphatemia cause low calcium?

A

Causes calcium to precipitate out of solution

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14
Q

What are the signs and symptoms of hypercalcemia?

A 
Cognitive dysfunction/fatigue
Polyuria
Addominal pain
Asymptomatic 
Elderly: volume depletion
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15
Q

What is the management of severe hypercalcemia?

A
  1. Manage ABCs: volume resuscitate
  2. calciuresis with loop diuretics
  3. Bisphaosphanates definitive tx
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16
Q

Risk factors for bone loss

A 
Age greater than 50
Low estrogen or testosterone 
white
Glucocorticoid use
Smoking, alcohol
Weight loss
Genetics
Chronic inflammatory diseases
17
Q

Risk factors for fragility fracture

A 
Low bone mass
Prior fragility fracture
Family history
Age greater than 65 
Chronic glucocorticoid use
18
Q

How is fracture risk assessed?

A

Use CAROC or WHO FRAX scores, do not use DXA as sole diagnostic tool

19
Q

Cause of hypercalcemia with high PTH

A

Primary hyperparathyroid

20
Q

Cause hypercalcemia with low PTH

A
  1. Malignancy (myeloma or lung)
  2. Vitamin d overdose
  3. Granulotmatous disease
21
Q

Cause of hypocalcemia with low PTH

A

Primary hypoparathyroid

22
Q

Cause of hypocalcemia with high PTH?

A

Normal vitamin d: chronic renal disease, hyperphosphatemia, calcium sequestering
Very low vitamin d: malabsorption, short gut, GI disease

23
Q

Osteoporosis

A

Decreased bone mass with disrupted bone architecture (but normal mineralization) leading to fragility

24
Q

When to we investigate secondary causes of osteoporosis and what tests to we do?

A
  1. If unclear risk or low bone mass outside of menopause
  2. Ca and possibly PTH
  3. Alkaline phosphatase
  4. TSH (hypo?)
  5. Phosphate (hypo?)
  6. SPEP (MM)
  7. Testosterone (hypogonad)
25
When do we measure 25-vitamin D?
When investigating: 1. Malabsorptive states 2. Non menopausal 3. Abnormal calcium
26
What drugs can cause osteoporosis?
``` chemo aromatase inhibitors progesterone based OCP PPI?? Glucocorticoids ```
27
Bisphosphanates
1. Mechanism: Inhibit osteoclasts which increases bone hardness 2. Indications: osteoporosis (more beneficial at higher risk), hypercalcemia tx 3. Side effects: jaw necrosis, atypical femur fracture 4. Regime: Give for 3-5 years then stop
28
Denosumab
1. Mechanism: Anti-RANK-L antibody, prevents osteoclast activation 2. Indications: post menopausal women with high fracture risk
29
Raloxifene
1. Mechanism: Estrogen receptor modulator
30
Estrogen
1. Mechanism: acts on osteoclasts to inhibit | 2. Side effects: increased risk CVD, cancer, stroke
31
Teriparatide
1. Mechanism: PTH: decreases osteoblast loss, increases new bone formation and bone mass
32
Rickets
``` Decreased mineralization (osteomalacia) of bone Look for bowed/knock knees, frontal bossing ```
33
Primary causes of pediatric osteoporosis
Osteogenesis imperfecta LRP5 heterozygous mutation Idiopathic juvenile osteoporosis
34
Drugs and endocrine causes of high calcium
Drugs: thiazides, lithium, vitamin A Endo: hyperthyroid, pheochromocytoma Other: immobilization
35
First line treatment hypercalcemia?
Volume resuscitate: must be done before use diuretics for calciuresis
36
Drugs and endocrine causes of high calcium
Drugs: thiazides, lithium, vitamin A Endo: hyperthyroid, pheochromocytoma Other: immobilization
37
First line treatment hypercalcemia?
Volume resuscitate: must be done before use diuretics for calciuresis
38
Treatment for chronic hypocalcemia
``` Oral calcium supplements Calcitriol supplements (more if severely deficient) ``` Aim for at or below lower limit normal for calcium
39
Indications for hyperparathyroid surgery
``` Symptomatic hypercalcemia Very high serum calcium CNS impairment Younger than 50 Bone Disease Chronic kidney disease ```

Endocrine (12 decks)

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