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MNE > Calcium Regulation > Flashcards

Calcium Regulation Flashcards

1
Q

Role of VITAMIN D

&

Vitamin D action on GI TRACT

A
  1. Calcium homeostasis: increase plasma Ca
  2. Synthesized sequentially in skin, liver, and kidneys
  3. Exerts effects directly on gastrointestinal tract
    - increases calcium absorption and to a lesser extent, phosphate
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2
Q

Vitamin D synthesis in skin depends on: (3)

A
  1. age (skin ineffecient >70yrs)
  2. Length of sun exposure
  3. UV strength exposure; latitude & season
  4. Ethnicity
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3
Q

Dietary sources of Vitamin D (4)

A
  1. Fatty fish
  2. Fish oils
  3. Dairy products, eggs
  4. Fortified milk, cereals, grains
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4
Q

25 hydroxyvitamin D

A
  1. storage form
  2. substrate dependent; not regulated
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5
Q

1-alpha hydroxylase

A
  1. Produces activated: 1,25 Vitamin D
  2. Stimulated by low calcium levels and low 25 hydroxyvitamin D
    - increased PTH
    - low phosphate
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6
Q

Vitamin D action on BONE

A
  1. Indirect action; improves bone health
  2. Deficiency causes decreased:
    - bone density
    - osteomalacia (soft bones)
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7
Q

Vitamin D action on KIDNEY

A
  1. Indrect action
  2. Deficiency: renal phosphate wasting due to increased PTH levels
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8
Q

Role of PARATHYROID HORMONE (PTH)

A
  1. Increase plasma calcium
  2. Synthesized in the parathyroid glands located in the neck
  3. Exerts effects directly on skeleton and kidneys
  4. Secreted by exocytosis in response to hypocalcemia
    - Calcium sensint receptor on cell membrane
    - As vitamin D decreases, only a small decrease in Ca is seen b/c of an increase in PTH to maintain levels
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9
Q

Parathyroid hormone action on BONE

A

Increases bone resorption by stimulating activity of osteoclasts (break down)

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10
Q

Parathyroid hormone action on KIDNEYS

A
  1. Increases renal calcium reabsorption
  2. Decreases renal phosphate reabsorption/increases secretion
  3. Promotes conversion of 25-hydroxyvitamin D –>

1,25-dihydroxyvitamin D

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11
Q

Parathyroid hormone actions on GI TRACT

A
  1. Indirect action
  2. Stimulates produciton of active form of Vit D —> increases absorption of calcium and to a lesser extend phosphate
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12
Q

Hyperparathyroidism

4 hormone levels

4 effects

A
  1. High calcium
  2. low phosphate
  3. normal 25; high 1,25
  4. HIGH PTH

Effects:

  1. Hypercalcemia
  2. hypophosphatemia
  3. osteoporosis
  4. nephrolithiasis (kidney stones)
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13
Q

Vitamin D toxicity

4 hormone levels

4 effects

A
  1. High calcium
  2. High phosphate
  3. HIGH 25; normal-high 1,25
  4. Low PTH

Effects:

  1. Hypercalcemia
  2. Hypercalciuria (nephrolithiasis, renal calcinosis, renal insufficiency)
  3. Hyperphosphatemia
  4. Inhibition of PTH secretion (reason why 1,25 vit D levels aren’t extremely high)
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14
Q

Hypoparathyroidism

4 hormone levels

2 effects

A
  1. Low calcium
  2. high phosphate
  3. normal 25; low 1,25
  4. LOW PTH

Effects:

  1. Hypocalcemia
    - paresthesias
    - muscle spasm
    - tetany
    - laryngospasm
    - seizures
  2. Hyperphosphatemia (due to lack of stimulation of secretion in kidneys)
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15
Q

Vitamin D deficiency

4 hormone levels

5 Effects

A
  1. Low calcium
  2. Low phosphate
  3. LOW 25; normal 1, 25
  4. High PTH

Effects:

Due to malabsorption

  1. Hypocalcemia
  2. Hypophosphatemia
  3. Myopathy: weakness, muscle pain
  4. Secondary hyperparathyroidism
  5. Inadequate bone mineralization
    - osteomalacia: not enough Ca to form correclty; excess osteoid
    - osteoporosis
    - Rickets: bowing of lower extremeties
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16
Q

Signs & Symptoms of Hypocalcemia: mild

A

Neuromuscular manifestations

  1. Circumoral numbness (tingling around mouth)
  2. Paresthesias hands and feet (cramping)
  3. Muscle cramps
17
Q

Signs & Symptoms of Hypocalcemia: severe

A

Neuromuscular manifestations

  1. QT prolongation; changes in EKG
  2. Chvostek’s sign: facial nerve outline-twitch in mouth, nerve, eye
  3. Carpopedal spasm: Trousseau’s sign (induce spasm or hand
  4. Laryngospasm (difficulty breathing)
  5. Tetany
  6. Focal or generalized seizures
18
Q

Symptoms of Hypercalcemia

A
  1. Fatigue
  2. Weakness
  3. Polydipsia
  4. Polyuria
  5. Nocturia
  6. Constipation
  7. Depression
  8. Headache
  9. Memory loss
  10. Arthralgias, myalgias
  11. Anorexia
  12. Nausea
  13. Heartburn
  14. Vomiting
19
Q

Signs of Hypercalcemia

A
  1. Hypercalcuria
  2. Nephrolithiasis
  3. Nephrocalcinosis
  4. Hematuria (from passage of stone)
  5. Renal insufficiency
  6. If due to excess PTH (decreased bone density and fracture)

MNE (16 decks)

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