39: Ca/Phosphate Homeostasis

Question 1

Distribution of Ca in ECF, ICF, and bones/teeth

Answer 1

ECF: 0.1%
ICF: 1%
Bones and teeth: 99%

Question 2

Total Ca that is protein bound vs ultrafilterable

Answer 2

Protein bound: 40%

Ultrafilterable: 60%

Question 3

Normal range for Ca and Pi in the blood

Answer 3

Ca: 10mg/dL
Pi: 2.5-4.5 mg/dL

Question 4

Two things that occur with Ca as we age

Answer 4

1. Decrease amount we absorb from dietary intake

2. Existing bones reabsorb faster than new bone is made -> osteopenia or osteoporosis

Question 5

S/S hypocalcemia

Answer 5

Hyperreflexia, spontaneous twitching, muscle cramps, tingling and numbness

Question 6

Two signs that are indicators of hypocalcemia (explain them)

Answer 6

1. Chvostek sign: twitch in facial muscle elicited by tapping facial nerve
2. Trousseau sign: carpopedal spasm upon inflation of BP cuff

Question 7

How does hypocalcemia cause tetany?

Answer 7

Reduces activation threshold for Na channels -> increased membrane excitability

Question 8

S/S hypercalcemia

Answer 8

Decreased QT interval, constipation, lack of appetite, polyuria, polydipsia, muscle weakness, hyperreflexia, lethargy, coma

Question 9

Concentration of Pi vs Ca in ECF

Answer 9

Are inversely related

Question 10

Distribution of Pi in bone, ICF, and plasma

Answer 10

Bone: 85%
ICF: 15%
Plasma: <1%

Question 11

Plasma Pi: % ionized, bound to protein, and complexed

Answer 11

84% ionized
10% bound to protein
6% complexed to cations

Question 12

What happens to PTH with chronic hypercalcemia?

Answer 12

Decreased synthesis and storage of PTH + breakdown of stored PTH

Question 13

What happens to PTH/parathyroids during chronic hypocalcemia

Answer 13

Increased synthesis and storage of PTH + hyperplasia of parathyroid glands

Question 14

What binds vitamin D in plasma?

Answer 14

Vitamin D binding protein

Question 15

Where are vitamin D receptors

Answer 15

In nucleus

Question 16

What does vitamin D do once it meets its receptor in order to be effective?

Answer 16

Receptor + vitamin D dimerize with another set -> become hydroxylated -> modulate gene transcription

Question 17

What happens with calcitonin with thyroidectomy and thyroid tumors

Answer 17

Thyroidectomy: decreased calcitonin, but no effect on Ca metabolism
Thyroid tumors: increased calcitonin, but no effect on Ca metabolism

Question 18

One of the most potent regulators of osteoblasts and osteoclast function

Answer 18

Estradiol-17B

Question 19

What can happen to pts treated with high levels of glucocorticoids?

Answer 19

Glucocorticoid induced osteoporosis

Question 20

How does PTH cause bone resoprtion in the long term?

Answer 20

Sustained levels shift balance to a relative increase in osteoclasts

Question 21

PTH role in SI

Answer 21

No direct action, works indirectly via vitamin D

Question 22

TRPV6 channel

Answer 22

Channel for Ca entry into intestinal ep from lumen

Question 23

Calbindin

Answer 23

Binds Ca to maintain Ca reservoir + shuttles it into blood

Question 24

The saying for primary hyperparathyroidism symptoms

Answer 24

Stones, bones and groans

Question 25

Treatment for primary hyperparathyroidism

Answer 25

Usually requires parathyroidectomy

Question 26

Treatment for hypoparathyroidism

Answer 26

Oral Ca supplement + active form of vitamin D

Question 27

Other name for Albright Hereditary Osteodystrophy

Answer 27

Pseudohypoparathyroidism Type 1A

Question 28

Type I and II of pseudovitamin D deficient rickets

Answer 28

Type I: decreased 1a-hydroxylase

Type II: decreased vitamin D receptor

Question 29

Nutritional osteomalacia

Answer 29

From GI disorder or suboptimal nutrition and inadequate sunlight, can also be caused by gastric bypass