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Endocrinology > Calcium > Flashcards

Calcium Flashcards

1
Q

What percent of calcium is free? What percent is bound to proteins?

A

50% free, 50% bound

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2
Q

As pH decreases, there is (more/less) bound calcium or __________.

A

less
hypercalcemia

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3
Q

As pH increases, there is (more/less) bound calcium or ____________.

A

more
hypocalcemia

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4
Q

As pH increases, the total calcium amount is the same but calcium replaces some of what molecule?

A

H+

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5
Q

Calcium and what other molecule maintain relatively constant free concentrations since they are inversely proportional?

A

phosphate (phosphorus)

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6
Q

PTH will (increase/decrease) calcium and (increase/decrease) phosphate.

A

increase
decrease

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7
Q

(T/F) More calcium is lost than is rebuilt in the adult.

A

False - equal amount

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8
Q

How is calcium obtained for rebuilding of bone?

A

through diet –> GI tract –> ECF –> kidneys (reabsorbed) –> bone

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9
Q

What 3 major hormones control calcium levels?

A

PTH
calcitonin
calcitriol (vitamin D3)

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10
Q

What is the source of parathyroid hormone (PTH)?

A

chief cells in parathyroid gland

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11
Q

What is the source of calcitonin?

A

parafollicular cells (C cells) in thyroid gland

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12
Q

What is the source of calcitriol?

A

skin, activated in kidney

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13
Q

What are the 3 major targets for calcium control?

A
  1. GI tract
  2. kidneys
  3. bone
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14
Q

Two actions of PTH in bone

A

up calcium resorption (stim osteoclasts)
up phosphate resorption (but less than Ca)

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15
Q

In the kidney, PTH acts to (increase/decrease) calcium reabsorption, (increase/decrease) phosphate reabsorption, and (increase/decrease) bicarbonate reabsorption.

A

increase
decrease
decrease

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16
Q

______ converts vitamin D to its active form in what organ?

A

PTH
kidney

17
Q

As PTH increases the circulating calcium, it is absorbed the intestines and the calcium increase (stimulates/inhibits) production of PTH via (positive/negative) feedback.

A

inhibits
negative

18
Q

(T/F) High enough calcium levels will stop PTH production.

A

False - never completely stops

19
Q

Vitamin D is a _______ which can be obtained through UV light of skin as (D2/D3) or by food as (D2/D3).

A

steroid
D3
D2

20
Q

Vitamin D begins as a steroid, is converted to ________ in the liver and then a ________ in the kidney.

A

secosteroid
hormone

21
Q

In the GI tract, vitamin D (increases/decreases) calcium absorption and (increases/decreases) phosphate absorption.

A

increases
increases

22
Q

How does vitamin D increase calcium absorption in the GI tract?

A

activates calcium channel proteins

23
Q

What action does vitamin D have on bone?

A

increases osteoclasts –> calcium resorption

24
Q

What action does vitamin D have on the kidney?

A

increases calcium reabsorption

25
Q

List the last 3 steps in the synthesis of vitamin D hormone and where it takes place.

A
  1. skin: 7-dehydrocholersterol in skin exposed to UV light –> cholecalciferol –> blood
  2. liver: 25-hydroxylase enzyme adds OH group –> 25-hydroxycholicalciferol
  3. kidney: PTH activates 1-a-hydroxylase which adds another OH group = calcitriol
26
Q

What is the structure of calcitonin? What unique link does it have which forms a loop?

A

32-amino acid polypeptide
cysteine-cysteine link

27
Q

In bone, calcitonin acts to (increase/decrease) calcium resorption and (increase/decrease) phosphate resorption.

A

decrease
decrease

28
Q

In the kidney, what happens to calcium and phosphate resorption in response to calcitonin?

A

decrease calcium resorption
decrease phosphate resorption

29
Q

Calcitonin acts on the kidney to increase the breakdown of what?

A

vitamin D

30
Q

What 2 actions does calcitonin cause in the GI tract?

A
  1. decrease gastrin secretion
  2. decrease calcium reabsorption
31
Q

Calcitonin binds to a receptor on ______ to inhibit its activity. What does this mean is the main driver?

A

osteoclast
osteoblasts (use calcium to build bone, reduce circulating calcium)

32
Q

What is the half-life for each?

  1. calcitonin
  2. PTH
  3. vitamin D (active)
A
  1. 5 min (short)
  2. <10 min (short)
  3. 4-6 hours (long)
33
Q

________ receptors are used for PTH and calcitonin while _______ receptors are used for vitamin D.

A

transmembrane
nuclear superfamily

Endocrinology (10 decks)

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