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BIOM2010 > Endocrine Control of Calcium and Bones > Flashcards

Endocrine Control of Calcium and Bones Flashcards

1
Q

State 4 important functions of calcium in the body

A
  1. nerve muscle excitability
  2. fusion of and secretion from storage vessels
  3. muscle contraction
  4. intracellular second messenger
  5. structural - skeleton/bone remodelling
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2
Q

Where is the majority of the calcium stored in the body? And what is it called?

A

99% found in bones and teeth - hydroxyapatite

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3
Q

What is the total concentration of Ca in ECF? How much is biologically active?

A

~2.5mM, and approximately half is ‘free’

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4
Q

Is calcium well absorbed by the body? Why/why not?

A

No, as it it highly charged

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5
Q

Name the three types of cells involved in the formation and resorption of bone

A

Osteoblasts
Osteocytes
Osteoclasts

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6
Q

Which type of bone cell monitors the bone matrix and has an essential role in exchanging the Ca between ECF and bone?

A

Osteocytes

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7
Q

What is the function of osteoblasts?

A

synthesise and secrete collagen and promote the deposition of CaPO4 crystals

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8
Q

What is the function of osteoclasts?

A

promote bone resorption

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9
Q

What is the purpose of the cortical and spongy bone?

A

Cortical = hard bone, mineralised for strength, 80%

Spongy =. trabecular bine, metabolically more active, big surface area, 20%

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10
Q

Is the dissolution of bone a fast or slow process?

A

Slow

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11
Q

How can calcium be quickly exchanged from bone into plasma?

A

Membrane bound Ca pump (hormonal control)

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12
Q

Explain a primary signal for bone resorption.

A

Expression of RANKL on osteoblasts and its interaction with RANK on osteoclast progenitors

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13
Q

What is RANK? Which cell is it present on?

A

receptor activator of nuclear factor kappa B (osteoclast progenitor cells)

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14
Q

What is RANKL? And which cell is it present on?

A

RANK ligand (osteoblasts)

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15
Q

Name the three hormones which regulate Ca metabolism and bone

A

Parathyroid hormone
Vitamin D3
Calcitonin

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16
Q

Which hormone is secreted by the chief cells of the parathyroid gland? And what is its overall action?

A

Parathyroid hormone

increase Ca2+ and decrease PO4 in plasma

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17
Q

What are the actions of the parathyroid hormone in the short term and long term?

A

Short term: stimulate Ca pump in osteocytes

Long term: stimulate osteoclasts and inhibit osteoblasts

18
Q

Explain the role of the kidney with regards to PTH

A

Decrease Ca loss by increasing tubular reabsorption of Ca2+ and decreasing tubular reabsorption of PO4

19
Q

What is the role of the GIT with regards to PTH?

A

Stimulates activation of Vitamin D3

20
Q

Which hormone involved in Ca metabolism is known as a pro-hormone?

A

Vitamin D

21
Q

Vitamin D can come from plants and animals, what are the respective terms for each?

A

Pro Vitamin D3 - 7-dehydro cholesterol

Pro Vitamin D2 - ergosterol

22
Q

What role does the sun have to play in the activation of Vitamin D?

A

The UV rays transform the vitamin d in skin (which is originally from diet) into its active form.

23
Q

Is the processing of Vitamin D in the liver regulated? What is the metabolite formed?

A

Not regulated

Calcifediol

24
Q

Is processing of Vitamin D is the kidneys regulated? What is the metabolic formed?

A

Highly regulated

Calcitriol

25
Q

What are the three main biological actions of Calcitriol in the blood?

A

Cell differentiation
Activation of osteoblasts
Calcium and phosphate homeostasis

26
Q

What is the overall MOA of Vitamin D3?

A

increase the amount of Ca in plasma

27
Q

Which hormone os produced in the thyroid gland in the c cells?

A

Calcitonin

28
Q

What is the overall MOA of calcitonin?

A

decrease Ca2+ in the plasma and increase PO4 in plasma (i.e., inhibits bone resorption

29
Q

Hyperparathyroidism is a disease of Ca metabolism. It involves which hormone and what is the direct consequence?

A

PTH hyper secretion which results in hypercalceamia

30
Q

What is the primary cause of hyperparathyroidism?

A

adenoma (cancer of parathyroid gland)

31
Q

What are the two secondary causes of hyperparathyroidism?

A

chronic renal failure

Nutritional

32
Q

What controls PTH release?

A

Plasma Ca2+ levels

33
Q

What are some of the effects of hyperparathyroidism?

A

Osteoporosis
Increased Ca2+ excretion (issues with kidney)
Decreased excitability of nerves and muscles - this seems unusual bc calcium is involved in excitation

34
Q

What is the main cause of hypoparathyroidism? And what can it lead to?

A

primary destruction of the parathyroid/thyroid gland (immune mediated or post-surgical), hypocalcaemia

35
Q

List three other causes of hypocalcaemia

A

pregnancy, lack of vitamin D, change in blood pH

36
Q

Hypocalcaemia is a serious condition - in what way can it cause death?

A

Increased neuromuscular excitability, death due to asphyxiation

37
Q

What is the MOA of the drug Calcitriol?

A

Increases Ca uptake from diet –> mobilises Ca from bones

38
Q

List three bisphosphonates that are used in the treatment of osteoporosis.

A

Risedronate, Alendronate, Zoledronate

39
Q

What is the MOA of the bisphosphonates?

A

Inhibit the activity of osteoclasts (effects can last months to years)

40
Q

Which SERM is used in osteoporosis? What is it MOA? Who are you more likely to treat with this drug?

A

Raloxefine, stimulate osteoblast activity, inhibit osteoclast activity. Women

41
Q

Why are women susceptible to osteoporosis?

A

Menopause = decrease in estrogen whereas the testosterone in men is converted to oestrogen in the bone

42
Q

What is the MOA of Denosumab?

A

inhibits RANKL, therefore decreases bone resorption

BIOM2010 (4 decks)

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