Calcium and Phosphorus Homeostasis

Question 1

forms of calcium

Answer 1

bound to albumin
complexed to anions
free ionized Ca2+ - bio active**

Question 2

hypocalcemia

Answer 2

hyperreflexia, twitching, cramps, tingling, numbnes

chvostek sign and trousseau sign

Question 3

chvostek sign

Answer 3

tapping facial nerve - twitching facial muscles

Question 4

trousseau sign

Answer 4

carpopedal spasm with inflation of BP cuff

Question 5

hypercalcemia

Answer 5

polyuria, constipation, hyporeflexia, lethargy, polydipsia

Question 6

changes in plasma protein concentration

Answer 6

alter total Ca concentration

-PTH sense change in ionized Ca and can correct

Question 7

change in anion concentration

Answer 7

alter ionized Ca
-change fraction complexed to anions

phosphate increase - ionized Ca decrease

Question 8

acid base balance

Answer 8

acidemia - excess H+ bound to albumin

-increase in ionized Ca2+

Question 9

alkalemia

Answer 9

free ionized Ca2+ decreased - hypocalcemia

Question 10

Ca homeostasis

Answer 10

kidney, bone, intestine

Question 11

bone resorption

Answer 11

(+) PTH, 1,25 Vit D

(-) calcitonin

Question 12

PTH

Answer 12

released from parathyroid gland with decreased plasma ionized Ca2+

Question 13

chief cells

Answer 13

of parathyroid gland - secrete PTH
-activity in N-terminal AAs

sense decrease in extracellular Ca2+ concentration

Question 14

magnesium

Answer 14

low levels stimulate PTH release

Question 15

PTH on kidney

Answer 15

increased Ca reabsorption

decreased P reabsorption

Question 16

PTH on bone

Answer 16

increased bone resorption

• act on osteoblasts - secrete cytokine
• osteoclast activity increases

Question 17

PTH on intestine

Answer 17

indirectly on Vit D > 1,25 Vit D

increased Ca absorption

Question 18

primary hyperparathyroidism

Answer 18

parathyroid adenomas
-increased PTH secretion

hypercalcemia, hypophasphateima

possible oxlalate stones

stones, bones, groans
-oxalate stones, bone resorption, constipation

Question 19

secondaray hyperparathyroidism

Answer 19

vit D deficiency, chronic renal failure
-secondary to hypocalcemia

-elevated PTH, Ca low or normal

Question 20

hypoparathyroidism

Answer 20

consequence of surgery
-autoimmune less common

low PTH, hypocalcemia, hyperphosphatemia

Tx: oral Ca supplement and active 1,25 Vit D

Question 21

pseudohypoparathyroidism

Answer 21

PTH increased
-Gs protein for PTH in kidney and bone defective

albrights hereditary osteodystrophy

hypocalcemia, hyperphosphatemia, short, obese, subQ calcification, short tarsels/carpals

Question 22

hypercalcemia of malignancy

Answer 22

lung or breast tumors secrete PTH-rp

all physiological action of PTH

circulating PTH low**

Tx: furosemide - inhibits renal Ca absorption
and etidronate - inhibits bone resorption

Question 23

familial hypocalciuric hypercalcemia

Answer 23

autosomal dominant
decreased urinary Ca, increased serum Ca

mutations in Ca sensing receptor in parathyroid glands

PTH secretion not inhibited

Question 24

calcitonin

Answer 24

from parafollicular, or C, cells of thyroid gland

stimulus - increased plasma Ca

inhibits osteoclast

Question 25

Vitamin D

Answer 25

promote mineralization of new bone from diet and in skin (UV light) kidney - 25 Vit D > 1,25 Vit D - stimulus - high Ca in serum - alters activity of a-alpha hydroxylase enzyme

Question 26

Vit D in intestine

Answer 26

1,25 - increased Ca and P absorption

Question 27

Vit D and kidney

Answer 27

increase Ca and P reabsorption

Question 28

Vit D and bone

Answer 28

stimulate osteoclast and bone resorption | -breakdown old bone to create new bone

Question 29

rickets

Answer 29

Vit D deficiency in children | -growth failure, skeletal deformities

Question 30

osteomalacia

Answer 30

vitamin D deficiency in adults | -bending and softening of bones

Question 31

Vit D resistance

Answer 31

kidney can't produce 1,25 Vit D - can be caused by chronic renal failure - can lead to osteomalacia

Question 32

CaSR

Answer 32

Ca sensing receptor | senses extracellular calcium and controls PTH secretion

Question 33

forms of VIt D

Answer 33

Vit D3 and Vit D2 - converted to 25 VIt D in liver kidney - 25 VIt D to 1,25 Vit D -enzyme - 1 alpha hydroxylase

Question 34

PTH independent hypercalcemia

Answer 34

thiazide diuretics immobilization** acute renal failure**

Question 35

acute renal failure

Answer 35

hypercalcemia

Question 36

chronic renal failure

Answer 36

hypocalcemia

Question 37

causes of hypocalcemia

Answer 37

Vit D deficiency liver failure hypoproteinemia - decreased albumin - decreased total Ca

Question 38

alkaline phosphatase

Answer 38

increased with more resorption of Ca from bone

Question 39

high calcium of malignancy

Answer 39

high Ca | low PTH

Question 40

primary hyperparathyroidism

Answer 40

high Ca | high PTH

Question 41

Vit D deficiency

Answer 41

high PTH | low Ca

Question 42

kidney faliure

Answer 42

very low Ca | very high PTH