Regulation of Calcium and Phosphate Metabolism Flashcards Preview

Endo/Repro Midterm > Regulation of Calcium and Phosphate Metabolism > Flashcards

Flashcards in Regulation of Calcium and Phosphate Metabolism Deck (104)
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1

Percent distribution of calcium in:

ECF
Plasma
ICF
Bones and teeth

ECF = 0.1%
Plasma = 0.5%
ICF = 1%
Bones and teeth = 99%

2

What forms of calcium exist in the blood?

Calcium exists in ionized form, bound to plasma proteins, or complexed in non-ionized form

Protein bound = 40%
Unfilterable = 60%

Of the unfilterable Ca, 10% is complexed to anions and 50% is ionized calcium

3

T/F: changes in plasma protein concentration alter the total Ca concentration in the opposite direction

False: changes in plasma protein concentration alter the total Ca concentration in the same direction as protein concentration

4

What are 3 ways of altering forms of Ca in the plasma?

Altering total Ca by changing plasma protein concentration (changes in same direction)

Altering ionized Ca by changing the fraction of Ca complexed with anions (changes anion concentration)

Altering ionized Ca by changing the fraction of Ca bound to proteins (albumin binds Ca and H)

5

If plasma [Pi] increases, the fraction of Ca that is complexed ________, thereby _______ ionized [Ca]

Increases; decreasing

6

How does plasma [Ca] change in conditions of acidemia vs. alkalemia?

Acidemia = high plasma [Ca] — high plasma [H], albumin binds more H, thereby increasing Ca

Alkalemia = low plasma [Ca] — low plasma [H], albumin binds more Ca, thereby decreasing Ca

7

What effect does hypocalcemia have on neuromuscular excitability?

Increases it, because more Ca is inside the cells

May lead to hypocalcemic tetany/spasticity

8

What effect does hypercalcemia have on neuromuscular excitability?

Depresses it; threshold shifts away from resting membrane potential

9

What are the regulators of plasma levels of calcium, thus controlling neuromuscular excitability?

PTH
Calcitonin
Calcitriol

10

Primary hyperparathyroidism and malignancy are clinical conditions related to _____levels of serum Ca

Elevated

11

Hypoparathyroidism, renal disease, and vit D deficiency are clinical conditions related to ___ serum Ca

Low

12

What are the 3 coordinated organ systems primarily involved in Ca homeostasis?

Bone
Kidney
Intestines

13

What hormone is responsible for bone formation from body calcium pool

Calcitonin

14

What hormones are responsible for bone resorption into body calcium pool?

PTH
Calcitriol

15

What hormones inhibit Ca excretion from kidneys?

PTH
Calcitriol
Calcitonin

16

What hormone is responsible for absorption of calcium from the GI tract into the body calcium pooL?

Calcitriol

17

About 1500 mg of Ca is taken in daily via the diet. The majority of this is excreted where?

Stool = 1300 mg

[200 mg excreted in urine]

18

Extracellular concentration of Pi is inversely correlated to that of _____.

Ca

19

Where is the majority of our phosphate stored?

85% in bone

[14% in cells, less than 1% serum]

20

What system primarily controls the fine tuning of phosphate levels?

Renal excretion

[renal tubular reabsorption is inhibited by PTH; reabsorption depends on transport maximum]

21

What are the 4 classic regulators of phosphate metabolism?

Dietary
Calcitriol
PTH
Renal tubular

22

Calcitriol regulation of phosphate metabolism

Calcitriol increases phosphorus resorption from bone and absorption from intestine

INCREASES Pi reabsorption in kidney

23

PTH regulation of phosphate metabolism

Phosphorus resorption directly from bone, and indirectly activates intestinal absorption through stimulation of calcitriol production

24

What endocrine factors directly or indirectly control NaPi cotransporter activity in the apical membrane?

PTH
Vitamin D
FGF23

25

What effect do insulin, GH, and thyroid hormone have on renal phosphate reabsorption?

Increase it

26

What effect do calcitonin, glucocorticoids, and ANP have on renal phosphate reabsorption?

Decrease it

27

What effect does a gain of function mutation have in FGFR3?

Achondroplasia

28

Endocrine FGF derived from bone, regulated by phosphate and vitamin D levels, which in turn regulate phosphate homeostasis

FGF23

29

3 renal effects of FGF 23

Directly downregulates NaPi transporters in kidney

Stimulates PTH to downregulate NaPi transporters in kidney

Decreases Calcitriol production in kidney

30

Where is PTH synthesized and secreted?

Chief cells of parathyroid gland