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Physiology II Exam 2 (Lauren) > L19-20 Calcium And Phosphate Regulation > Flashcards

L19-20 Calcium And Phosphate Regulation Flashcards

1
Q

Free calcium fluctuates (hardly at all/a lot)

A

Hardly at all. Changes less than 2%

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2
Q

99% of calcium in your body is in what form?

A

Crystalline form in teeth and bone

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3
Q

If you eat 1000mg of calcium, how much do you poop and pee out that day?

A

1000mg

(You absorb about 350 mg, but you also secrete 350mg of your body’s calcium back into the intestine and urine. Plus 650mg from diet didn’t even get absorbed)

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4
Q

How much of plasma calcium is in the ionized active form

A

50%

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5
Q

What is the normal plasma concentration of calcium

A

10mg/dL

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6
Q

What is required to absorb calcium from the intestine and from the bone

A

1,25-Dihydroxycholecalciferol aka Vitamin D

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7
Q

What effect does calcitonin have on bone resorption?

A

Inhibits it

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8
Q

What are the target organs of parathyroid hormone

A

Bone

Intestine

Kidney

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9
Q

What causes PTH to be released

A

DROP IN BLOOD CALCIUM*****

PTH then acts on kidney, bone and intestine to normalize blood calcium levels

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10
Q

What cells in the parathyroid release PTH?

A

Chief cells**

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11
Q

Does the parathyroid have any follicular cells

/

A

No

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12
Q

What is the effect of PTH on vitamin D?

A

Promotes the activation of Vitamin D to increase calcium absorption from food

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13
Q

What is the affect of PTH on bone

A

Activated osteoclasts to release calcium and phosphate into blood

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14
Q

What are the 2 calcium pools in your bones?

A

Stable pool

Labile pool

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15
Q

What kind of bone is in the stable pool?

A

Mature mineralized bone composed primarily of hydroxyapatite

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16
Q

What kind of bone is in the labile pool?

A

Bone fluid composed primarily of amorphous crystals

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17
Q

Which pool releases calcium And phosphate into the blood faster?

A

Labile pool

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18
Q

Which pool would your body use if you needed to make a quick small adjustment to blood calcium

A

Labile pool

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19
Q

How do calcium and phosphate get from the labile pool into the blood

A

The pool undergoes osteolytic osteolysis and then there is a rapid exchange with the ECF

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20
Q

Within the bone, what separates the bone itself from the plasma within the canals?

A

Ostocytic-osteoblastic bone membrane

This has a large surface area and a small movement of calcium= large influx of calcium and phosphate into the plasma from the bone fluid

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21
Q

What are the 2 effects of PTH on the kidney?

A
  1. Stimulates calcium reabsorption
  2. Inhibits PO4 reabsorption

(Calcium IN, Phosphate OUT)

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22
Q

Elimination of PO4 in the kidney also causes what other substance to increase in the urine?

A

Urine cAMP

because you need cAMP to eliminate PO4

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23
Q

What lab value could you measure to track a patient’s PTH status?

A

cAMP levels in the urine

increase PTH= increased cAMP in the urine

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24
Q

How does PTH activate vitamin D?

A

Stimulates 1-α hydroxylase activity in the kidney

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25
Q

What are the 2 steps required for vitamin D to become activated?

A
  1. Addition of (OH) on carbon 25 in the liver via the enzyme 25-hydroxylase
  2. Addition of (OH) on carbon 1 in the kidney via the enzyme 1α-hydroxylase

Results in 1,25-dihydroxycholecalciferol

STEP 2 ONLY HAPPENS IF YOU DON’T GET ENOUGH CALCIUM FROM YOUR DIET**

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26
Q

Is vitamin D3 considered a prohormone?

A

Yes

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27
Q

What are the 2 names for active vitamin D3

A

1,25-dihydroxyvitamin D3

1,25-dihydroxycholecalciferol

28
Q

If you have an adequate amount of calcium in your diet, what happens to the Vitamin D3 you eat/your skin makes

A
  1. Vitamin D3 goes to Liver.
  2. (OH)group is added to carbon 25 by 25-hydroxylase
  3. Goes to kidney
  4. (OH) group is added to carbon 24***
  5. Produces inactive 24,25-dihydroxycholecalciferol
29
Q

What effect does Vitamin D have on the bones?

A

It synergizes with PTH to remodel the bone and to mobilize calcium and PO4.

30
Q

True or false:

Vitamin D + PTH are required for bone growth

A

True

31
Q

What effect does vitamin D have on the kidney?

A

Reabsorption of calcium

Reabsorption of Phosphate**!!!

(It has the opposite effect on PO4 reabsorption as PTH)

32
Q

What effect does Vitamin D have on the small intestine?

A

It makes more Calbindin, which then allows the body to absorb more calcium from the diet

33
Q

What is calbindin

A

It is inside small intestine cells and it absorbs calcium out of the foods you eat

34
Q

What effect do glucocorticoids have on PTH?

A

They increase PTH secretion

Too much corticosteroids= lots of bone resorption=fracture risk

35
Q

Type II diabetics and obese people have lots of cortisol. Why does this put them at in increased fracture risk?

A

Corticosteroids increase the secretion of PTH which can cause too much bone resorption and put them at risk

36
Q

What effect does Vitamin D have on PTH secretion?

A

Decreases it

37
Q

What are the possible risks of taking too much vitamin D?

A

Fracture risk

Hypercalcemia

38
Q

What does calcitonin do?

A

Decreases plasma calcium and PO4

39
Q

How does calcitonin decreases plasma Calcium and PO4?

A

Inhibits bone resorption

Inhibits tubular reabsorption in Kidney

40
Q

What effect does calcitonin have on the intestine?

A

NONE*!!!**!!

41
Q

Calcitonin does the opposite of PTH except in what organ?

A

In the small intestine.
PTH causes increased calcium reabsorption

Calcitonin has NO EFFECT on the small intestine.

42
Q

What causes calcitonin release?

A

Increased plasma calcium

43
Q

Why do we have calcitonin

A

We dont really know

  • when we don’t have calcitonin, we don’t get hypercalcemia
  • excessive calcitonin does not produce hypocalcemia
  • may prevent hypercalcemia after a meal?
44
Q

What is the only time we think calcitonin might have an important role?

A

In pregnancy

45
Q

What disease:

“Stones, bones and groans”

A

Primary hyperparathyroidism

46
Q

What is the most common cause of primary hyperparathyroidism?

A

A PTH-secreting tumor

47
Q

If your patient has primary hyperparathyroidism, what do you expect to see in
Plasma:

Urine:

A

Plasma; hypercalcemia and hypophosphatemia

Urine: increased phosphate, cAMP, and hypercalciuria

48
Q

What are the complications of hyperparathyroidism?

A

Muscle weakness **

Kidney stones

Osteoporosis, ostemalacia (bones)

Constipation (groans)

49
Q

What causes hypoparathyroidism?

A

Thyroid surgery

50
Q

What is Trousseau’s Sign and in what condition might you see it?

A

It is spasms of the hand when you inflate a BP cuff around the arm.

Seen in hypoparathyroidism (low calcium)

51
Q

Low calcium causes muscle (weakness/hyperactivity)

A

Hyperactivity

52
Q

If you have a tumor that is secreting PTH-related peptide, what will happen to calcium and phosphate levels?

A

Hypercalcemia

Hypophosphatemia

(Same thing as if it was real PTH)

53
Q

If you have a tumor that is secreting PTH-related peptide, what will PTH levels be?

A

Low**

PTH secretion is inhibited by hypercalcemia

54
Q

“PTH resistance” describes what condition?

A

Pseudohypoparathyroidism

aka

Albright’s hereditary osteodystrophy

55
Q

What is pseudohypoparathyroidism?

A

An autosomal dominant disorder where PTH binds to its receptor, and then nothing happens due to defective signal transduction

56
Q

In pseudohypoparathyroidism, what are the levels of:

PTH:

Calcium:

Phosphate:

A

PTH: high

Calcium: low

Phosphate: high

57
Q

What will someone with pseudohypoparathyroidism look like?

A

Short

Short neck

Obese

Short 4th finger and 4th toe

58
Q

Primary hyperparathyroidism effect on:
PTH:

Vitamin D:

Bone resorption:

Urine:

Calcium:

Phosphate:

A

PTH: high

Vitamin D: high (effect on 1α-hydroxylase)

Bone resorption: high

Urine: high PO4, Ca, and cAMPT

Calcium: high

Phosphate: low

59
Q

Surgical hypoparathyroidism effect on:
PTH:

Vitamin D:

Bone resorption:

Urine:

Calcium:

Phosphate:

A

PTH: low

Vitamin D: low (effect on 1α-hydroxylase)

Bone resorption: low

Urine: low PO4 and cAMP

Calcium: low

Phosphate: high

60
Q

Pseudohypoparathyroidism effect on:
PTH:

Vitamin D:

Bone resorption:

Urine:

Calcium:

Phosphate:

A

PTH: high

Vitamin D: low

Bone resorption: low

Urine: low PO4 and cAMP

Calcium: low

Phosphate: high

61
Q 
Humoral hypercalcemia (tumor that secretes PTH-related peptide) effect on:
PTH:

Vitamin D:

Bone resorption:

Urine:

Calcium:

Phosphate:

A

PTH: Low

Vitamin D: no effect** calcium uptake not increased in presence of PTH-rp

Bone resorption: high

Urine: increased PO4, Ca, and cAMP

Calcium: high

Phosphate: low

62
Q

What causes rickets?

A

Deficiency of vitamin D in childhood

63
Q

What is osteomalacia?

A

Deficiency of vitamin D in adulthood

Either due to diet or intestinal surgery that affects absorption

64
Q

What muscle effects would you expect to see in rickets or osteomalacia?

A

Hypocalcemic Tetany

65
Q

Why would low vitamin D cause you to break your bones a lot (rickets/osteomalacia)

A

No vitamin D= no calcium absorption and high levels of PTH due to the hypocalcemia = bone resorption

Physiology II Exam 2 (Lauren) (4 decks)

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