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Block 3 Week 5 Meg > Keef: Parathyroid Gland > Flashcards

Keef: Parathyroid Gland Flashcards

1
Q

Total body content of Ca+

A

1,300g

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2
Q

Total body content of Phosphorus

A

600g

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3
Q

Where is most calcium (99%) and phosphate (86%) located?

A

in bones and teeth

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4
Q

Is there more calcium INSIDE cells or OUTSIDE cells?

A

More inside cells (0.9%)

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5
Q

Is there more phosphorus INSIDE cells or OUTSIDE cells?

A

More inside cells (14%)

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6
Q

Calcium variation in plasma is about (blank)% per day. Most calcium is in what form?

A

1-2%; ionized form

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7
Q

Phosphorus variation in plasma is about (blank)% per day. Most phosphorus is in what form?

A

50-150%; HPO4(2-)

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8
Q

We ingest about 1000mg of calcium per day. How much of this is reabsorbed? How much of this is excreted in urine?

A

30% absorbed

1% excreted

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9
Q

We ingest about 900mg of phosphate per day. How much of this is reabsorbed? How much of this is excreted in urine?

A

60% reabsorbed

10% excreted

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10
Q

Calcium enters epithelial cells of duodenum and jejunum down its electrochemical gradient. It requires (blank) channels.

A

TRP Ca+ channels

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11
Q

Once inside the intestinal cells, calcium is bound by (blank) so that intracellular [Ca+] does not increase too much.

A

calbindin

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12
Q

To get out of the intestinal cells and into the interstitial space, calcium undergoes primary active transport via a (blank) or secondary active transport via a (blank).

A

Ca+/ATPase; Ca+/Na+ exchanger

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13
Q

In the duodenum and jejunum, is calcium absorbed actively or passively?
In the ileum, is absorption active or passive?

A

active; passive

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14
Q

In the duodenum, jejunum, and ileum, Pi gets into intestinal cells via ACTIVE transport. What does it require? Once inside the intestinal cells, it can travel down its gradient into the interstitial space.

A

Na+

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15
Q

In the kidney, 70% of Ca+ is reabsorbed in the proximal tubule. Is this paracellular or transcellular? Throughout the rest of the nephron, is reabsorption paracellular or transcellular?

A

paracellular; transcellular

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16
Q

How much of Ca+ is excreted from nephron?

A

1%

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17
Q

What effect does PTH have on calcium reabsorption?

A

PTH stimulates Ca+ reabsorption via the G-protein GS, which stimulates cAMP, activates PKA, and enhances transcellular movement of Ca+ by increasing TRP channels

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18
Q

Ca+ enters cells in the distal nephron by moving down its gradient through TRP channels and carrier proteins. Once in the cell, it binds to (blank). To get out of the cell and into the blood, it can exit through Ca+/ATPase or Ca+/Na+ exchanger.

A

Calbindin

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19
Q

In the proximal tubule, about 80% of phosphate is reabsorbed. Is this paracellular or transcellular?

A

transcellular

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20
Q

How much of phosphate is excreted from the nephron?

A

10%

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21
Q

What effect does PTH have on phosphate reabsorption in the nephron?

A

It inhibits phosphate reabsorption

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22
Q

Phosphate is reabsorbed into intestinal cells along with (blank). It exits out into the interstitial space/blood stream via anion exchange.

A

Na+

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23
Q

What two things make up mature compact bones?

A
  1. osteoid (collagen)

2. hydroxyapatite crystals

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24
Q

Bone remodeling is an adaptive process.
Growth > resorption until what age?
Resorption > growth after what age?

A

20-30 years

40+

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25
Q

Bone disorder: increased osteoid + mineral

A

osteopetrosis

26
Q

Bone disorder: “soft bones,” demineralization, rickets in children

A

osteomalacia

27
Q

Bone disorder: decreased osteoid + mineral

A

osteoporosis

28
Q

Drugs used for treatment of osteoporosis:
3 drugs decrease osteoclast bone resorption
1 drug activates bone formation

A

bisphosphates, calcitonin, estrogen

PTH

29
Q

Rapid, non-hormonal regulation of plasma calcium occurs in these two ways

A
  1. protein bound calcium

2. exchange with bone

30
Q

Long term, hormonal regulation of plasma calcium occurs via these three ways

A
  1. PTH
  2. calcitriol (active Vit D)
  3. calcitonin
31
Q

Cells within the parathyroid gland with Ca+ sensing receptors that release parathyroid hormone

A

chief cells

32
Q

When extracellular Ca+ is high, what happens to PTH release?

A

decreased PTH release

33
Q

When extracellular Ca+ is low, what happens to PTH release?

A

increased PTH release

34
Q

Released from C cells of the thyroid gland in response to increased serum Ca+ levels. Released in opposition to PTH.

A

calcitonin

35
Q

Is calcitonin essential for regulation of serum calcium levels?

A

No; PTH much more important

36
Q

Calcitonin and parathyroid hormone have (blank) effects on bone resorption

A

opposing

37
Q

If [Ca+]o is above normal, thyroid releases (blank). What does this do to osteoclast activity?

A

calcitonin; decreases osteoclast activity

38
Q

If [Ca+]o is below normal, thyroid releases (blank). What does this do to osteoclast activity?

A

PTH; increases osteoclast activity

39
Q

In the kidney, 25-hydroxycholecalcigerol is converted to (blank), which is the active form of Vitamin D. This is why patients with kidney failure must supplement with Vit D.

A

calcitriol

40
Q

What is the enzyme that takes Vit D to its active form? What two things can stimulate this enzymatic step?

A

25-hydroxyvitamin D3 1 alpha-hydroxylase;

  1. release of PTH
  2. decreased plasma [Pi]
41
Q

What is the DIRECT effect of PTH on Pi excretion, which overrides the effect of Vit D on Pi excretion?

A

PTH INCREASES Pi EXCRETION

42
Q

What effect does calcitriol (Vit D) have on Ca+ and Pi in bone? In the kidneys? In the intestines?

A

In bone: increases Ca+ and Pi mobilization
In kidneys: decreases Ca+ and Pi excretion
In intestines: increases Ca+ and Pi absorption

43
Q

(blank) is essential for life. Death by hypocalcemic tetany can occur if [Ca]o falls below 2.1 mM/L. What are some of the symptoms of hypocalcemic tetany?

A

PTH; CATS go numb - convulsions, arrhythmias, tetany, and numbness

44
Q 
What does hypoparathyroidism do to the following?
Calcium
Phosphate
PTH
Alkaline phosphate
A

Calcium: decreased
Phosphate: increased
PTH: decreased
Alkaline phosphate: no change

45
Q 
What does pseudohypoparathyroidism do to the following?
Calcium
Phosphate
PTH
Alkaline phosphate
A

Calcium: decrease
Phosphate: increase
PTH: increase
Alkaline phosphate: no change

46
Q 
What does osteomalacia/rickets do to the following?
Calcium
Phosphate
PTH
Alkaline phosphate
A

Calcium: decrease
Phosphate: decrease
PTH: increase
Alkaline phosphate: increase

47
Q 
What does chronic renal failure do to the following?
Calcium
Phosphate
PTH
Alkaline phosphate
A

Calcium: decrease
Phosphate: increase
PTH: increase
Alkaline phosphate: increase

48
Q 
What does Vit D intoxication do to the following?
Calcium
Phosphate
PTH
Calcium in urine
A

Calcium: increase
Phosphate: increase
PTH: decrease
Calcium in urine: INCREASE

49
Q 
What does primary hyperparathyroidism do to the following?
Calcium
Phosphate
PTH
Calcium in urine
A

Calcium: increase
Phosphate: decrease
PTH: increase
Calcium in urine: increase

50
Q

Most common cause of hypoparathyroidism? Treatment?

A

injury during head and neck surgery

restore/maintain Ca+ levels, Vit D supplements

51
Q

In hypoparathyroidism, there is LESS release of PTH from parathyroid glands. Main effect?

A

[Ca+] decreased

[Pi] increased

52
Q

Lack of response to PTH; most commonly due to a genetic defect in the PTH pathway.

A

pseudohypoparathyroidism

53
Q

Main effect of pseudohypoparathyroidism?

A

[Ca+] decreased
[Pi] increased
[PTH] high, but not being “sensed”

54
Q

Softening of the bone because of a loss of calcium in the bone material; can be caused by
inadequate vitamin D intake and/or disorders that interfere with the absorption of Ca+ from intestine

A

osteomalacia/Rickets

55
Q

PTH stimulates osteoblast alkaline phosphatase activity in blood and is therefore an indicator of enhanced (blank)

A

bone remodeling

56
Q

Main effect of osteomalacia/rickets?

A

[Ca+] and [Pi] are low because there is impaired reabsorption or not enough Vit D to stimulate reabsorption. [AP] levels will be high, because osteoclasts are stimulated to retrieve Ca+ from bone

57
Q

Loss of kidney function and 1alpha-hydroxylase (forms active Vit D) activity

A

chronic renal failure

58
Q

Main effect of renal failure?

A

No Vit D –> minimal Ca+ reabsorption.
Plasma phosphate will increase, because you can’t excrete it effectively.
Metabolic acidosis as a result of kidney failure and increased PTH will both increase bone breakdown in an attempt to increase plasma Ca+. So [AP] high.
JUST AWFUL.

59
Q

Too much Vitamin D

A

Too much Ca+ reabsorption, so PTH will decrease.

This will lead to higher plasma phosphate levels. Calcium in urine!!!

60
Q

Primary hyperparathyroidism

A

Too much PTH, causes too much Ca+ reabsorption. Increased Pi excretion. Loss of Ca+ in urine.

61
Q

Ca+ sensing receptor in chief cells of parathyroid gland work mainly by what mechanism?
Ca+ sensing receptors in the kidney work mainly by what mechanism?

A

Inhibit PTH secretion

Inhibit reabsorption of Ca+

Block 3 Week 5 Meg (8 decks)

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