9 Parathyroid

Question 1

what does a vitamin D deficiency cause in children? adults?

Answer 1

children=rickets

adults=osteomalacia

Question 2

what do chief cells do?

Answer 2

secrete PTH

Question 3

what do oxyphil cells do?

Answer 3

fuction unknown

Question 4

what are the normal levels of calcium in the blood?

Answer 4

9-10mg/dl

Question 5

what does PTH do the calcium and phosphate?

Answer 5

increases calcium levels by bone reabsorbtion, gut absorption, and increased reabsorbtion in kidney.
increases phosphate reabsorbtion from bone, but increases renal secretion of phosphate.

Question 6

what are the normal phosphate levels in the blood?

Answer 6

2.5-4.5 mg/dl

Question 7

T/F Only free Ca+ is active?

Answer 7

true

Question 8

how does PTH increase reabsorbtion of phosphate and calcium from the bone?

Answer 8

1) rapid osteolysis
2) activates osteoclasts (new and old ones indirectly through osteoblasts)
3) innactivates osteoblastic activity
4) increases calcium pump activity moving Ca+ out of bone.

Question 9

how do the osteoclasts attach to the bone?

Answer 9

they use integrins to bind to vitronectins.

Question 10

PTH causes the kidney to do what?

Answer 10

1) decrease reabsorbtion of phosphate
2) increase Ca+ reabsorbtion
3) conversion of 25 hydroxycholecalciferol to 1,25 dihydroxycholecalciferol which acts on the gut to help reabsorb both calcium and phosphate.

Question 11

what is another name for 1,25 dihydrocholecalciferol?

Answer 11

calcitriol

Question 12

what mainly regulates PTH secretion?

Answer 12

Ca+ levels in the blood.

Question 13

what effect do PKC and internal calcium have on PTH?

Answer 13

They both inhibit the release of PTH. They prevent synthesis and exocytosis.

Question 14

How does calcium inhibit secretion of more PTH?

Answer 14

it binds to the calcium receptor of the chief cell and activates a G protein. The G protein activates PLC which makes DAG and IP3. IP3 increases intracellular calcium levels and DAG increases PKC. Both (Ca+ and PKC) inhibit PTH synthesis and secretion.

Question 15

an inactivation mutation in the calcium receptor of a chief cell would lead to what?

Answer 15

hypercalcemia because of too much PTH release.

Question 16

what disease should you think of when you see increased neuromuscular excitability with increased tingling in fingers and toes?

Answer 16

hypoparathyroidism with associated hypocalcemia

Question 17

what is carpopedal tetany?

Answer 17

muscle twitch/spasm in arm and leg

Question 18

how do you treat hypoparathyroidism?

Answer 18

active form of vitamin D and exogenous Ca+

dont give PTH because its broken down too quickly

Question 19

what do you usually see with hyperparathyroidism?

Answer 19

depression of CNS
muscle weakness
cystic fibrosis osteitis
rise in alkaline phosphatase activity
elevation of urinary cAMP levels

Question 20

where do you get calcitonin? what does it do?

Answer 20

parafollicular cells (C cells)
Works opposite to PTH

Question 21

what does calcium do in the adult?

Answer 21

very little. only acts as a short term regulator of calcium ion concentrations in the blood.

Question 22

does calcitonin have an effect on phosphate?

Answer 22

yes like PTH it lowers phosphate levels.

Question 23

Alternate expression of the Calcitonin gene can yield CGRP which does what? and where?

Answer 23

It acts as a vasodilator in the brain.

Question 24

what are the steps to make active vitamin D starting with 7dehydrocholesterol in the skin? Liver? Kidney?

Answer 24

7 dehydrocholesterol
cholecalciferol [Vitamin D3]
25 hydroxycholecalciferol
1,25 dihydroxycholecalciferol

Question 25

what enhances the conversion of 25 hydocholecalciferol to 1,25 dihydrocholecalciferol?

Answer 25

vitamin D deficiency calcium deficiency phosphate deficiency increased PTH secretion

Question 26

what factors influence 25 hydroxycholecalciferol to be converted to its inactive form of 24,25 dihydrocholecalciferol?

Answer 26

vitamin D sufficiency hypercalcemia hyperphosphatemia

Question 27

what effects does 1,25 dihydrocholecalciferol have on the intestines?

Answer 27

1) induces the calcium binding protein calbindin to form in the cytoplasm 2) increases Ca+/Na+ exchanges on basolateral membrane

Question 28

T/F calbindin is an important blood transport protein that helps increase Ca+ half life in the blood?

Answer 28

false, Calbindin is only found in the cell's cytoplasm

Question 29

what is the major mechanism in which calcium enters the gut?

Answer 29

through paracellular transport

Question 30

which cells have Vitamin D receptors?

Answer 30

every tissue in the body except osteoclasts. They rely on osteoblast and paracrine hormones.

Question 31

what do you see with rickets in children?

Answer 31

malabsorbtion of vitamin D bones lacking tensile strength tetany of respiratory muscles

Question 32

what do you see with osteomalacia?

Answer 32

1) steatorrhea (failure to absorb fat) 2) renal rickets (kidney cant make active vitamin D) 3) congenital hypophosphatemia (failure of the kidneys to reabsorb adequate amounts of phosphate)

Question 33

how do you treat someone with congenital hypophosphatemia?

Answer 33

give them phosphate

Question 34

T/F PTH is only involved in Ca+ and PO4 regulation?

Answer 34

false, it has a lot to do with overall health and disorders can lead to some types of cancers

Question 35

does vitamin D stimulate serotonin release?

Answer 35

yes, and it causes changes in mood.