Calcium and Phosphate

Question 1

The labile pool is in direct contact with the osteocytic-osteoblastic bone membrane which contains many _________ which is why Ca2+ can be released so quickly into the central canal

Answer 1

PTH activated Ca2+-ATPase pumps

Question 2

PTH activates vitamin D in the kidney my stimulating _______________ activity

Answer 2

stimulating 1-alpha hydroxylase

Question 3

In the cells, where is most of the phosphate (more than 80%)?

Answer 3

mitochondria

the rest is in the cytosol

Question 4

What do patients with Pseudohypoparathyroidism look like?

Answer 4

short stature
short neck
obese
shortened 4th metatarsal and metacarpal

Question 5

Which “pool” of the bone responds to acute changes and PTH stimulation

Answer 5

labile pool

Question 6

What enzyme converts vitamin D3 to 25-hydroxyvitamin D3?

By adding what?

Answer 6

25-hydroxylase

OH to Carbon 25

Question 7

Where is the first step of vitamin D activation?

Answer 7

liver

Question 8

What % of calcium in the plasma is in the ionized active form?

Answer 8

50%

Question 9

complications of hypoparathyroidism

Answer 9

1. hypocalcemia induced tetany
2. hyperreflexia
3. spontaneous twitching
4. muscle cramps
5. convulsions

Question 10

Effects of excessive PTH-rp on the intestines

Answer 10

no intestinal effect

calcium uptake is not increased in the presence of PTH-rp

Question 11

increased cortisol or diabetes has what effect on PTH

Answer 11

increased

Question 12

increased phosphate excretion by the kidney can be measured by measuring ________ in the urine

Answer 12

cAMP

Question 13

Calcium is excreted mostly by the _____, and partially by the ______

Answer 13

mostly by the GI

partially by the kidney

Question 14

“stones, bones, and groans” =

Answer 14

primary hyperparathyroidism

Question 15

complications of Primary hyperparathyroidism

Answer 15

1. osteoporosis, osteomalacia
2. kidney stones
3. muscle weakness

Question 16

Which “pool” of the bone undergoes resorption– slow breakdown of crystals and liberation of Ca and PO4 into the ECF

Answer 16

stable pool

Question 17

Effects of excessive PTH-rp

plasma Ca =
plasma PO43- =
plasma PTH =

Answer 17

plasma Ca = increased
plasma PO43- = decreased
plasma PTH = decreased

Question 18

The addition of ______ to _______ creates inactive vitamin D3

Answer 18

OH to carbon 24

24,25-dihydroxycholecalciferol

Question 19

What two effects does PTH have on the kidney?

What effect does it have in relation to the kidney that is not a “direct effect”

Answer 19

1. stimulates Ca reabsorption
2. inhibits PO4 reabsorption

PTH also activates vitamin D by stimulating 1-alpha hydroxylase activity in the kidney

Question 20

Vitamin D is inactive when it enters the blood from the skin or diet and it is called ___________

Answer 20

Vitamin D3

prohormone

Question 21

Effects of Pseudohypoparathyroidism

PTH =
serum Ca =
serum PO4 =

Answer 21

PTH = increased… but ineffective
serum Ca = decreased
serum PO4 = increased

Question 22

increased PTH = increase bone resorption = increased risk of

Answer 22

bone fracture

Question 23

Parathyroid gland release parathyroid hormone (PTH) from _______ cells

Answer 23

chief cells

Question 24

of the 1% of Ca2+ in the body that is not in the teeth and bone,

0. 9% =
1. 1 % =

Answer 24

0. 9% = soft tissues, ER, mitochondria, membranes
1. 1 % = plasma

(half of plasma is bound, half is free ionized)

Question 25

Vitamin D action on the bone:

Answer 25

synergizes with PTH to stimulate resorption and remodeling and to mobilize calcium and phosphate

Question 26

Ca10(PO4)6(OH)2 -- hydroxyapatite which bone "pool"?

Answer 26

stable pool

Question 27

Roles of phosphate:

Answer 27

1. energy related pathways (metabolic) 2. cofactors (NAD, etc) 3. 2nd messengers

Question 28

Hypoparathyroidism is usually caused by

Answer 28

inadvertent consequence of thyroid surgery for treatment of cancer or Graves' disease

Question 29

Effects of excessive PTH-rp urine PO4 = urine Ca2+ = urine cAMP =

Answer 29

urine PO4 = increased urine Ca2+ = increased urine cAMP = increased

Question 30

what enzyme converts 25-hyroxyvitamin D3 to 1,25-dihydroxyvitamin D3? By adding what?

Answer 30

1a-hydroxylase OH to Carbon 1

Question 31

Primary hyperparathyroidism is most commonly caused by

Answer 31

PTH-secreting adenoma

Question 32

Vitamin D action on the kidney

Answer 32

calcium reabsorption | phosphate reabsorption

Question 33

If 1000mg of Ca2+ is ingested in the diet, what is the net absorption of Ca2+ (and eventually excreted by the kidney if Ca2+ levels are normal)

Answer 33

200 mg which means 800mg is excreted by the GI

Question 34

What is the active hormone of vitamin D3?

Answer 34

1,25-dihydroxycholecalciferol or 1,25-dihydroxyvitamin D3

Question 35

muscle weakness = muscle tetany/hyperactive = hypo/hyperparathyroidism?

Answer 35

muscle weakness = hyperparathyroidism | muscle tetany/hyperactive = hypoparathyroidism

Question 36

PTH on the kidney plasma PO4 = urine PO4 = plasma Ca = urine cAMP =

Answer 36

plasma PO4 = decrease urine PO4 = increase plasma Ca = increase urine cAMP = increase

Question 37

Pseudohypoparathyroidism is also called

Answer 37

Albright's hereditary osteodystrophy

Question 38

calcitonin decreases plasma Ca and PO4 by inhibiting:

Answer 38

bone resorption | tubular reabsorption

Question 39

CaHPO4:2H2O -- amorphous crystals which bone "pool"?

Answer 39

labile pool

Question 40

Phosphate distribution: 85% = 15% =

Answer 40

``` 85% = bone and teeth 15% = muscle ```

Question 41

99% of Ca2+ is in ______ form found in the _____

Answer 41

crystalline | teeth and bone (1 and 2 kg)

Question 42

Primary hyperparathyroidism ``` Plasma Ca = Plasma PO43 = urine Ca = urine PO43 = urine cAMP = ```

Answer 42

``` Plasma Ca = increased Plasma PO43 = decreased urine Ca = increased ---(spills over!) urine PO43 = increased urine cAMP = increased ```

Question 43

With normal Ca2+ intake, which form of vitamin D3 is produced?

Answer 43

inactive form 24,25-dihydroxycholecalciferol

Question 44

The __________ separates the bone itself from the plasma within the canals

Answer 44

osteocytic-osteoblastic bone membrane

Question 45

Activated vitamin D targets the intestine, bone, and kidney to collectively regulate __________ synthesis, and _____ and _____ levels in the plasma

Answer 45

calbindin synthesis | Ca2+ and PO43- levels in the plasma

Question 46

What is calbindin?

Answer 46

buffer protein of calcium in the intestines

Question 47

Total calcium free and bound in the blood =

Answer 47

~10mg/dL

Question 48

Where does the second step of vitamin D activation occur?

Answer 48

kidney

Question 49

What is the theorized reason for calcitonin

Answer 49

may protect against excessive bone resorption or when demand for Ca increases in pregnancy, lactation, and growth

Question 50

Hypoparathyroidism Plasma PTH = Plasma Ca = Plasma PO4 =

Answer 50

Plasma PTH = decreased Plasma Ca = decreased Plasma PO43 = increased phosphate cannot be excreted without PTH

Question 51

25-hydroxylase converts vitamin D3 to ________ | in the liver

Answer 51

25-hydroxyvitamin D3

Question 52

calcitonin does not have an effect on _____ whereas PTH does

Answer 52

intestines

Question 53

PTH effect on labile pool of bone

Answer 53

osteolytic osteolysis for fast release of Ca and PO4 liberation into the ECF

Question 54

Humoral hypercalcemia of is caused by

Answer 54

malignant cell clusters that secrete PTH-related peptide (PTH-rp)

Question 55

Vitamin D action on the small intestine

Answer 55

increase expression of calbindin | increase calcium absorption

Question 56

excess vitamin D supplementation has what effect on PTH

Answer 56

decreased but all the effects of PTH still exist from too much vitamin D