Bones and Calcium Flashcards

1
Q

What is the principle reservoir for calcium and potassium?

A

Bone.

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2
Q

What is osteoporosis?

A

The breaking of bones due to calcium deficiency.

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3
Q

What is osteopenia?

A

Weakening of bones (not as bad as osteroporosis)

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4
Q

What is osteopetrosis?

A

The hardening of bones, causing them to become inflexible and brittle.

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5
Q

Why is the regulation of calcium important?

A
  1. Bone structure
  2. Excitability of cells
  3. Intracellular signalling
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6
Q

Where are the blood’s three sources of calcium/phosphate?

A

Bone, kidney, and heart.

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7
Q

What two hormones are most important in calcium regulation?

A

Vitamin D3 and PTH

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8
Q

What are the two cells in bone?

A

Osteoblasts and osteoclasts

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9
Q

What effect does D3/PTH have on bone?

A

Increases breakdown of matrix for bone resportion.

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10
Q

How are osteoclasts activated?

A

Secretion of RANK from osteoblasts after activation by PTH/D3 activates osteoclast production.

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11
Q

What is the net effect of PTH?

A

Bone: increase calcium/phosphate resorption into blood
Kidney: increase calcium absorption but increase phosphate excretion

Stimulates vitamin D processing in kidney

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12
Q

Why is phosphate excreted via PTH?

A

Calcium and phosphate form a precipitate.

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13
Q

How is vitamin D metabolized?

A
  1. Vitamin D3 converted to 25-OH-D3 in liver (by 25-hydroxenase)
  2. Forms either 1,25-OH-D3 or 24,25-OH-D3
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14
Q

When is 1,25-OH-D3 (CALCITRIOL) formed?

A

Low calcium, PTH

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15
Q

When is 24, 25-OH-D3 (SECALCIFEROL) formed?

A

High calcitriol, high calcium.

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16
Q

What is the net effect of D3?

A
  1. Kidney: increased calcium and phospate reabsorption
  2. Promotes bone resorption
  3. Promotes uptake of phosphate and calcium from gut.
17
Q

What are calcium levels sense by?

A

Calcium receptors in the parathyroid.

18
Q

What is hypocalcemia?

A

Low levels calcium.

19
Q

What are short term resolutions to hypocalcemia?

A

Calcium or D3 metabolites.

20
Q

What is the acute effect of hypocalemia?

A
  1. Hyperexcitability of cells, causing Trousseau’s sign. May lead to seizures and spasms if unresolved.
21
Q

What are long term dangers of hypocalemia?

A

Secondary hyperparathyroidism; increased PTH levels causing bone resorption and osteoporosis.

22
Q

What is typically the cause of secondary hyperparathyroidism?

A

Hypoparathyroidism, Vitamin D deficiency

23
Q

What is hypercalcemia?

A

High levels of calcium

24
Q

What are acute effects of hypercalcemia?

A

Loss of cellular excitability.

25
Q

What is the typical cause of hypercalcemia (long term)?

A

Primary hyperparathyroidism; overactivity via tumor.

26
Q

How is primary hyperparathyroidism treated?

A

Resection of the parathyroid and subsequent treatment via therapeutics: calcimimetics and bone protectants.

27
Q

What gender is osteoporosis most common in? Why?

A

Post-menopausal women due to lack of estrogen (which builds up bones)

28
Q

How is osteoporosis treated in post-menopausal females?

A

Hormone replacement, estrogen mimetics

29
Q

What are common causes of osteoporosis?

A

Glucocorticoid administration, hyperparathyroidism.

30
Q

What are bisphosphonates?

A

Inhibit osteoclasts by binding to bone matrix (contain phosphates, can bind to calcium) to kill osteoclasts and inhibit glucocorticoids.