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Endocrine - Troutmanm > Calcium and Parathyroids > Flashcards

Calcium and Parathyroids Flashcards

1
Q

Why is calcium important?

A 
Nerve conduction
Bone formation 
Muscle function
Blood coagulation
Cerebral and cardiac function
Capillary permeability
Cell growth and division
Neurotransmitter action
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2
Q

How much calcium is contained in the body? and where is it located?

A

Body contains 1-2 kg of calcium

98% in skeleton***
0.03% in plasma
0.1% in ECF
1% in cells

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3
Q

How does plasma calcium present?

A

50% Ionized (active form)***
41% protein bound (primarily albumin)
9% combined with anions (diffusible)

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4
Q

Which form of calcium is the most important?

A

IONIZED

Most important form for calcium functions on heart, the nervous system, and bone formation

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5
Q

What % of bone calcium is readily exchangable?

A

Equilibrates with bone Ca++, but only 0.5% of bone calcium is readily exchangeable

The rest is slowly exchangeable

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6
Q

What does hypocalcemia cause?

A

Nervous system excitement

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7
Q

How does the nervous system excitement occur with hypocalcemia?

A

Increased neuronal permeability to Na, easy action potentials

50% ion/ 35% total decrease leads to spontaneous discharges

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8
Q

What happens with hypocalcemia?

A

Tetany, seizures
Most common in hand: carpopedal spasm
Or face: Chvosteks sign: tapping facial nerve leads to twitching

Longer QT (can develop R on T)

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9
Q

How does hypercalcemia manifest?

A

muscle weakness

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10
Q

Nervous system depression happens with hypercalcemia, how does this manifest?

A

Short QT, long PR interval, constipation, anorexia

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11
Q

What is the treatment for hypercalcemia?

A

Maintain UOP, hydrate, administer mithramycin in severe cases

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12
Q

How much phosphorous is in the body? and where is it located?

A

1kg

85 % skeletal
15% muscle/tissue
1% ECF

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13
Q

Phospherous circulates in plasma 12% _____

A

protein bound

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14
Q

Why do phos levels fluctuate more than Ca levels?

A

Levels fluctuate significantly more than ca++ because phos moves between ECF and bone as well as between ECF and ICF

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15
Q

is the effects of phos minimal or maximal with large fluctuations?

A

minimal

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16
Q

How does phos enter the ECF?

A

GI, ICF, bone

Easily absorbed in GI

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17
Q

How does phos leave?

A

via urine, ICF, bone

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18
Q

What is the major control site of phos?

A

Kidney

Urinary excretion balances GI intake
PTH increases urinary excretion
Calcitonin to a lesser extent
GI absorption increased by 1,25 D3

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19
Q

How many glands does the parathyroid have?

A

4

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20
Q

Where are they parathyroid glands located?

A

Located behind the upper and lower poles of the thyroid

very small in size

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21
Q

What cells do the parathyroid glands contain?

A

They contain mainly chief cells and oxyphil cells

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22
Q

*** What do chief cells secrete?

A

parathyroid hormone

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23
Q

What is synthesis and secretion of the parathyroid hormone related to?

A

calcium concentrations in the blood

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24
Q

What are parathyroid glands enlarged from?

A

Enlarged from prolonged stimulation, pregnancy, lactation

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25
Q

What does a decrease in calcium concentration in the ECF cause?

A

increases the secretion of PTH

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26
Q

What does a increase in calcium concentration in the ECF cause?

A

decreases the activity of the parathyroid gland

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27
Q

What is another name for Vit D

A

Cholecalciferol

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28
Q

What does PTH, Vit D, and calcitonin help with?

A

All help with reabsorption of Ca from the proximal tubules of the kidney

29
Q

*** PTH Actions: Increases bone resorption to mobilize ______

A

calcium and phosphate

30
Q

*** What does bone resorption mean?

A

Bone resportion is the process by which osteoclasts break down bone and release calcium from bone fluid to blood

31
Q

Is bone resorption fast or slow?

A

Rapid: activation of bone cells for rapid reabsorption

Delayed: activates/proliferates osteoclasts for bone matrix breakdown

32
Q

What does PTH do in regard to Ca and the kidney?

A

Increases reabsorption of Ca++ in the kidney’s distal tubules

33
Q

What does PTH do in regard to Phos and the kidney?

A

Decreases reabsorption of phosphate in the renal tubules

34
Q

*** What does PTH increase the production of?

A

Increases the production of 1,25-dihydroxycholecalciferol

Vit D metabolite which enhances intestinal Ca++ absorption

35
Q

*** What is a major stimulus for 1,25-dihydroxycholecalciferol?

A

low serum Ca++ level

36
Q

Increases in PTH result in:
Serum -
Urine -

A

Serum: Increased calcium, decreased phosphate

Urine: Decreased calcium, increased phosphate

37
Q

Increased PTH results in increased excretion of _____, _____, _____ by reabsorbing mire _____, _____, _____

A

phosphate, potassium, and sodium

calcium, magnesium, hydrogen

(this happens largely in distal tubules and collecting ducts)

38
Q

Where is calcitonin produced?

A

in the parafollicular (clear or C cells) of the thyroid

39
Q

Calcitonin has the opposite effect of what?

A

parathyroid hormone

40
Q

What does Calcitonin do to Ca levels? How?

A

decreases Ca levels

Inhibits bone resorption
Increases urinary excretion of calcium

Immediate: decreases osteoclastic activity and osteolysis of osteocytes
Delayed: Decreases osteoclast formation

41
Q

Calcitonin effects of serum Ca and Phos

A

Decreased calcium

Decreased phosphate

42
Q

Calcitonin effects of urine Ca and Phos

A

Increased calcium excretion

Increased phosphate excretion

43
Q

Calcitonin: Exact role unclear as excess or deficiency do not lead to defects in bone or calcium metabolism
Effect is weak

A

this is just a statement…

44
Q

Hoe does Vit D have an effect on Ca?

A

Vitamin D has a potent effect to increase calcium absorption from the intestinal tract

45
Q

Vitamin D has important effects on both bone _____ and bone ______

A

deposition

absorption

46
Q

*** Vitamin D is NOT itself an active substance, but must be converted to its active product ______

A

1,25-dihydroxycholecalciferol

47
Q

How is Vit D3 formed?

A

formed in the skin by exposure to sunlight

48
Q

Where is vitamin D3 is converted to 1,25-dihydroxycholecalciferol at?

A

in the liver

49
Q

GI absorption of Ca is increased by

A

Vit D

50
Q

Urinary excretion of Calcium is decreased by _____ and enhanced by _____

A

PTH

calcitonin

51
Q

Bone resorption of calcium is increased by ____ and inhibited by _____

A

PTH

calcitonin

52
Q

How does hypoparathyroid usually happen?

A

Usually a result of surgical damage to the gland during thyroid surgery

53
Q

After surgical removal of the parathyroid glands, when can you see a fall in calcium levels?

A

24-72 hours

54
Q

What do low levels of Ca result in?

A

Tetany

  • calcium ion interferes with membrane transport
  • interferes with the relaxation of the muscle

Muscle cramps
Grand mal seizures
Cardiovascular collapse

55
Q

Treatment of hypoparathyroidism

A

PTH – expensive, short half life

High calcium and Vit D intake
Occasionally 1/25-D3 necessary

56
Q

*** What happens when you have hypomag in relation to hypocalcemia?

A

Hypomagnesemia can cause hypocalcemia resistant to calcium

Must treat first with magnesium
Magnesium suppresses the release of PTH

57
Q

What is primary hyperparathyroidism?

A

inappropriate hypersecretion of PTH resulting in hypercalcemia

58
Q

What does hyperparathyroidism result in?

A

Results in hypercalcemia, hypercalciuria, hypophosphatemia, hyperphosphaturia, bone demineralization

Effects cardiac function (shortens QT interval, depresses relaxatioin)

Causes Kidney stone formation as Ca++ mobilized from bone must eventually be excreted by kidneys

59
Q

What is the most common cause of hyperparathyroidism?

A

parathyroid hyperplasia or parathyroid tumor

60
Q

What state may stimulate the parathyroids?

A

pregnancy

61
Q

What is Vit D deficiency usually due to?

A

Often due to fat malabsorption syndrome

Inadequate sunlight

Decreased absorption of calcium and phosphate, decreased serum calcium and phosphate, increased PTH and increased bone resorption

62
Q

What is Vit D deficiency in adults?

A

osteomalacia

63
Q

What is Vit D deficiency in children?

A

Rickets: bones fail to mineralize, epiphyses fail to fuse, epiphyseal plates widen and bowing and fractures occur

64
Q

One gram of Calcium Chloride contains the equivalent amount of ionized calcium as

A

3 grams of Calcium Gluconate

65
Q

Calcium is indicated for treatment of hyperkalemia induced EKG changes because of its

A

cell membrane stabilizing effects

66
Q

*** Calcium is indicated in patients with hypotension associated with either _____ or _____

A

calcium channel blockers or beta adrengergic blockers

67
Q

Calcium is indicated in cases of ________ as may occur in parturients being treated for preeclampsia

A

magnesium toxicity

68
Q

Calcium is contraindicated in patients with ______ as it may cause lethal arrhythmias

A

digoxin toxicity

Endocrine - Troutmanm (7 decks)

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