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Endocrine > Metabolic Bone Disease > Flashcards

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
Q

When do we measure 25-vitamin D?

A

When investigating:

  1. Malabsorptive states
  2. Non menopausal
  3. Abnormal calcium
26
Q

What drugs can cause osteoporosis?

A 
chemo
aromatase inhibitors
progesterone based OCP
PPI??
Glucocorticoids
27
Q

Bisphosphanates

A
  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
Q

Denosumab

A
  1. Mechanism: Anti-RANK-L antibody, prevents osteoclast activation
  2. Indications: post menopausal women with high fracture risk
29
Q

Raloxifene

A
  1. Mechanism: Estrogen receptor modulator
30
Q

Estrogen

A
  1. Mechanism: acts on osteoclasts to inhibit

2. Side effects: increased risk CVD, cancer, stroke

31
Q

Teriparatide

A
  1. Mechanism: PTH: decreases osteoblast loss, increases new bone formation and bone mass
32
Q

Rickets

A 
Decreased mineralization (osteomalacia) of bone
Look for bowed/knock knees, frontal bossing
33
Q

Primary causes of pediatric osteoporosis

A

Osteogenesis imperfecta
LRP5 heterozygous mutation
Idiopathic juvenile osteoporosis

34
Q

Drugs and endocrine causes of high calcium

A

Drugs: thiazides, lithium, vitamin A
Endo: hyperthyroid, pheochromocytoma
Other: immobilization

35
Q

First line treatment hypercalcemia?

A

Volume resuscitate: must be done before use diuretics for calciuresis

36
Q

Drugs and endocrine causes of high calcium

A

Drugs: thiazides, lithium, vitamin A
Endo: hyperthyroid, pheochromocytoma
Other: immobilization

37
Q

First line treatment hypercalcemia?

A

Volume resuscitate: must be done before use diuretics for calciuresis

38
Q

Treatment for chronic hypocalcemia

A 
Oral calcium supplements
Calcitriol supplements (more if severely deficient)

Aim for at or below lower limit normal for calcium

39
Q

Indications for hyperparathyroid surgery

A 
Symptomatic hypercalcemia
Very high serum calcium
CNS impairment
Younger than 50
Bone Disease
Chronic kidney disease

Endocrine (12 decks)

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