Lect 24 - Calcium Homeostasis

Question 1

What is the difference between the edema seen in CHF and that in hypothyroidism?

Answer 1

Hypothyroidism –> non-pitting edema

CHF –> pitting edema

Question 2

In regards to edema, what is a characteristic of hyperthyroidism?

Answer 2

Pretibial myxedema

Question 3

What percentage of calcium is found in bodily fluids?

Answer 3

1%

Question 4

What percent of plasma calcium is in free or ionized form?

Answer 4

50%

Question 5

Plasma calcium that is not free calcium is bound to what molecules?

Answer 5

1) phosphate
2) citrate
3) albumin

Question 6

When you have a calcium deficiency, what percentage can the GI tract absorb from your diet?

Answer 6

90%

Question 7

What is the normal percentage of calcium that you get from diet?

Answer 7

30%

Question 8

If calcium is deficient from your diet, where do you get it?

Answer 8

Bones

Question 9

What does an alkalotic pH do to serum calcium? Acidotic pH?

Answer 9

Alkalotic pH decreases serum calcium.

Acidotic pH increases serum calcium.

Question 10

What percentage of phosphate in your body is in your bones?

Answer 10

86%

Question 11

Where is the rest of the phosphate in your body other than your bones?

Answer 11

ECF

Question 12

In what form is the majority of the phosphate in your ECF?

Answer 12

Organic form

Question 13

In what circumstances is calcitonin important?

Answer 13

For calcium regulation in utero

Question 14

What are the two main hormones that control calcium homeostasis?

Answer 14

PTH and calcitriol

Question 15

What happens in cases of excess calcium and/or phosphate in serum?

Answer 15

They might precipitate out and form salts

Question 16

What is the most important regulator of ECF calcium?

Answer 16

PTH

Question 17

What stimulates PTH production?

Answer 17

Low serum calcium

Question 18

What second messengers are used in parathyroid cells?

Answer 18

IP3/DAG/Ca and PLC

Question 19

At what two sites does PTH work?

Answer 19

1) osteoblasts in bone

2) kidneys

Question 20

What are the cytokines released by PTH-stimulated osteoblasts?

Answer 20

1) M-CSF (macrophages)
2) RANK (Receptor activator of nuclear factor κ B)
3) IL-6

Question 21

What effects does PTH have on the kidney?

Answer 21

increased reabsorption of calcium

decreased reabsorption of phosphate

Question 22

How does PTH affect absorption of calcium from the GI tract?

Answer 22

Indirectly through Vit D

Question 23

What catalyst is used to turn 7-dehydrocholesterol into cholecalciferol? Where does this take place?

Answer 23

1) UV light

2) skin

Question 24

Where does cholecalciferol turn into 25-hydroxyvitamin D? Which enzyme catalyzes this reaction?

Answer 24

1) liver

2) 25-hydroxylase

Question 25

Where does 25-hydroxyvitamin D turn into 1,25-hydroxyvitamin D? Which enzyme catalyzes this reaction?

Answer 25

1) kidney | 2) 1-hydroxylase

Question 26

Which hormone regulates the hormone 1-hydroxylase in the kidney?

Answer 26

PTH

Question 27

Which two transporters are upregulated on the basolateral membrane of duodenal cells by vitamin D?

Answer 27

1) calcium-sodium exchanger | 2) calcium-hydrogen exchanger

Question 28

What are two causes of primary hyperparathyroidism?

Answer 28

1) ectopic parathyroid tissue | 2) parathyroid tumor

Question 29

What are the clinical consequences of hyperparathyroidism?

Answer 29

1) elevated serum calcium 2) phosphaturia 3) polyuria 4) calciuria/kidney stones 5) shortened QT interval 6) risk for peptic ulcer disease 7) cystic lesions on bone

Question 30

What are four causes of secondary hyperparathyroidism?

Answer 30

1) diet deficient in Vitamin D 2) fat malabsorption leading to vitamin D deficiency 3) kidney disease (unable to synthesize vitamin D) 4) increased need for calcium

Question 31

What are the symptoms and signs of primary hypoparathyroidism?

Answer 31

1) tetany 2) prolonged QT interval 3) low serum calcium

Question 32

What is Chvostek sign?

Answer 32

Percussing the cheek in front of the ear to produce facial spasms

Question 33

What is Trousseau sign?

Answer 33

Occluding blood flow to the lower arm to induce carpopedal spasm