Keef: Parathyroid Gland

Question 1

Total body content of Ca+

Answer 1

1,300g

Question 2

Total body content of Phosphorus

Answer 2

600g

Question 3

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

Answer 3

in bones and teeth

Question 4

Is there more calcium INSIDE cells or OUTSIDE cells?

Answer 4

More inside cells (0.9%)

Question 5

Is there more phosphorus INSIDE cells or OUTSIDE cells?

Answer 5

More inside cells (14%)

Question 6

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

Answer 6

1-2%; ionized form

Question 7

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

Answer 7

50-150%; HPO4(2-)

Question 8

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

Answer 8

30% absorbed

1% excreted

Question 9

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

Answer 9

60% reabsorbed

10% excreted

Question 10

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

Answer 10

TRP Ca+ channels

Question 11

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

Answer 11

calbindin

Question 12

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).

Answer 12

Ca+/ATPase; Ca+/Na+ exchanger

Question 13

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

Answer 13

active; passive

Question 14

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.

Answer 14

Na+

Question 15

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?

Answer 15

paracellular; transcellular

Question 16

How much of Ca+ is excreted from nephron?

Answer 16

1%

Question 17

What effect does PTH have on calcium reabsorption?

Answer 17

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

Question 18

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.

Answer 18

Calbindin

Question 19

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

Answer 19

transcellular

Question 20

How much of phosphate is excreted from the nephron?

Answer 20

10%

Question 21

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

Answer 21

It inhibits phosphate reabsorption

Question 22

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

Answer 22

Na+

Question 23

What two things make up mature compact bones?

Answer 23

1. osteoid (collagen)

2. hydroxyapatite crystals

Question 24

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

Answer 24

20-30 years

40+

Question 25

Bone disorder: increased osteoid + mineral

Answer 25

osteopetrosis

Question 26

Bone disorder: "soft bones," demineralization, rickets in children

Answer 26

osteomalacia

Question 27

Bone disorder: decreased osteoid + mineral

Answer 27

osteoporosis

Question 28

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

Answer 28

bisphosphates, calcitonin, estrogen | PTH

Question 29

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

Answer 29

1. protein bound calcium | 2. exchange with bone

Question 30

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

Answer 30

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

Question 31

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

Answer 31

chief cells

Question 32

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

Answer 32

decreased PTH release

Question 33

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

Answer 33

increased PTH release

Question 34

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

Answer 34

calcitonin

Question 35

Is calcitonin essential for regulation of serum calcium levels?

Answer 35

No; PTH much more important

Question 36

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

Answer 36

opposing

Question 37

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

Answer 37

calcitonin; decreases osteoclast activity

Question 38

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

Answer 38

PTH; increases osteoclast activity

Question 39

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.

Answer 39

calcitriol

Question 40

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

Answer 40

25-hydroxyvitamin D3 1 alpha-hydroxylase; 1. release of PTH 2. decreased plasma [Pi]

Question 41

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

Answer 41

PTH INCREASES Pi EXCRETION

Question 42

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

Answer 42

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

Question 43

(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?

Answer 43

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

Question 44

``` What does hypoparathyroidism do to the following? Calcium Phosphate PTH Alkaline phosphate ```

Answer 44

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

Question 45

``` What does pseudohypoparathyroidism do to the following? Calcium Phosphate PTH Alkaline phosphate ```

Answer 45

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

Question 46

``` What does osteomalacia/rickets do to the following? Calcium Phosphate PTH Alkaline phosphate ```

Answer 46

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

Question 47

``` What does chronic renal failure do to the following? Calcium Phosphate PTH Alkaline phosphate ```

Answer 47

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

Question 48

``` What does Vit D intoxication do to the following? Calcium Phosphate PTH Calcium in urine ```

Answer 48

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

Question 49

``` What does primary hyperparathyroidism do to the following? Calcium Phosphate PTH Calcium in urine ```

Answer 49

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

Question 50

Most common cause of hypoparathyroidism? Treatment?

Answer 50

injury during head and neck surgery | restore/maintain Ca+ levels, Vit D supplements

Question 51

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

Answer 51

[Ca+] decreased | [Pi] increased

Question 52

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

Answer 52

pseudohypoparathyroidism

Question 53

Main effect of pseudohypoparathyroidism?

Answer 53

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

Question 54

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

Answer 54

osteomalacia/Rickets

Question 55

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

Answer 55

bone remodeling

Question 56

Main effect of osteomalacia/rickets?

Answer 56

[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

Question 57

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

Answer 57

chronic renal failure

Question 58

Main effect of renal failure?

Answer 58

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.

Question 59

Too much Vitamin D

Answer 59

Too much Ca+ reabsorption, so PTH will decrease. | This will lead to higher plasma phosphate levels. Calcium in urine!!!

Question 60

Primary hyperparathyroidism

Answer 60

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

Question 61

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?

Answer 61

Inhibit PTH secretion | Inhibit reabsorption of Ca+