Exam 3: Calcium And Phosphate Regulation

Question 1

What are the target organs of PTH?

Answer 1

Bone, kidney, and intestine

Question 2

When is PTH released?

Answer 2

When there is a drop in calcium

Question 3

What the main effects of PTH?

Answer 3

• stimulates osteoclasts to release phosphate and calcium ions into the blood
• increase Ca absorption from food
• promotes activation of vitamins D and increases calcium reabsorption

Question 4

What are the two calcium pools in bone?

Answer 4

-stable pool and the labile pool

Question 5

What is the stable calcium pool?

Answer 5

Consists of mature mineralized bone composed primarily of hydroxyapatite.
Undergoes slow breakdown of crystals and liberation of Ca and PO4

Question 6

What is the labile calcium pool?

Answer 6

Consists of bone fluid composed primarily of amorphous crystals
Undergoes osteolytic osteolysis for fast release of Ca and PO4

Question 7

What is the site of bone resorption?

Answer 7

The stable pool

Question 8

How is calcium moved from the labile pool into the plasma?

Answer 8

PTH activated Ca pumps located in the osteocytic osteoblastic bone membrane

Question 9

How is calcium moved from the stable pool to the plasma?

Answer 9

By means of PTH induced dissolution of the bone

Question 10

How do osteoblasts control osteoclast activity?

Answer 10

• OPG

- Osteoprotegerin ligand (OPGL or RANKL)

Question 11

How does PTH actually cause bone resorption?

Answer 11

• PTH targets the osteoblasts, which releases OPGL
• when OPGL/RANKL alone binds to the osteoclasts, this stimulates bone resorption
• When OPG is co-released, it binds with OPGL on the osteoclast and prevents resorption

Question 12

What is mutated in Cleidocranial dysplasia?

Answer 12

Runx2 mutation

Question 13

What are the two effects of PTH in the kidney?

Answer 13

1)stimulates Ca reabsorption and inhibits PO4 reabsorption

Question 14

What activates vitamin D? How?

Answer 14

PTH activates vitamin D by stimulating 1-alpha hydroxylase activity in the kidney and converts he inactive precursor into the active form

Question 15

What does activated vitamin D do?

Answer 15

Targets the intestine, bone, and kidney to collectively regulate calbindin synthesis, as well as Ca and PO4 levels in the plasma

Question 16

What are the effects of Vitamin D in the bone?

Answer 16

Synergies with PTH to stimulate resorption and remodeling and to mobilize calcium and phosphate

Question 17

What are the effects of vitamin D in the kidney?

Answer 17

Promotes calcium reabsorption from the distal tubule and proximal tubular reabsorption of phosphate

Question 18

What is Vitamin Ds affect in the small intestine?

Answer 18

Increases calcium absorption by increasing expression of Calbindin. Calcium diffuses into the cells, binds to calbindin, and its pumped across the basolateral membrane by Ca-ATPase

Question 19

What hormones enhance the effects of PTH?

Answer 19

Glucocorticoids

Question 20

What stimulates calcitonin release?

Answer 20

Increased plasma calcium level

Question 21

What are the effects of calcitonin?

Answer 21

Calcitonin decreases plasma Ca and PO4 by inhibiting bone resorption and tubular reabsorption

Question 22

What is the most common cause of primary hyperparathyroidism?

Answer 22

PTH secreting adenoma

Question 23

What are the effects of primary hyperparathyroidism?

Answer 23

Plasma: Hypercalcemia and hypophosphatemia

Urine: Increased levels of phosphate, cAMP, and calcium (kidney spillover)

Question 24

What are the complications that can occur from primary hyperparathyroidism?

Answer 24

Osteoporosis/osteomalacia, kidney stones, and muscle weakness

“Stones, bones, and groans)

Question 25

What is hypoparathyroidism usually caused by?

Answer 25

Inadvertent consequence of thyroid surgery

Question 26

What are the characteristics of hypoparathyroidism?

Answer 26

-Low PTH, Hypocalcemia, hyperphosphatemia

Question 27

Wha are the signs and symptoms of hypoparathyroidism?

Answer 27

-Positive trousseaus sign, hypocalcemia may induce tetany, hyperreflexia, spontaneous twitching, and convulsions

Question 28

If PTH levels are low, yet calcium is very high, what can be the cause?

Answer 28

Humoral hypercalcemia of malignancy ( malignant cells secrete PTH related peptide and bind to PTH receptor

Question 29

What is pseudohypoparathyroidism also known as?

Answer 29

Albrights hereditary osteodystrophy

Question 30

What is Albrights hereditary osteodystrophy?

Answer 30

Autosomal dominant disorder associated with a defective Gs in the kidney and bone
-May cause elevated PTH, hypocalcemia, and hyperphosphatemia

Question 31

What is the phenotype of Albrights hereditary osteodystrophy?

Answer 31

Short stature, short neck, obesity, and shortened 4th metatarsals/metacarpals

Question 32

In primary hyperparathyroidism, what happens to the following:
PTH
Bone reabsorption
Plasma Ca
Plasma phosphate

Answer 32

PTH: Increased
Bone reabsorption: increased
Plasma Ca: increased
Plasma phosphate: decreased

Question 33

In surgical hypoparathyroidism, what happens to the following:

PTH
Bone reabsorption
Plasma Ca
Plasma phosphate

Answer 33

PTH: decreased
Bone reabsorption: decreased
Plasma Ca: decreased
Plasma phosphate: increased

Question 34

In pseudohypoparathyroidism, what happens to the following:

PTH
Bone reabsorption
Plasma Ca
Plasma phosphate

Answer 34

PTH: increased
Bone reabsorption: decreased
Plasma Ca:decreased
Plasma phosphate: increased

Question 35

In humoral hypercalcemia, what happens to the following:

PTH
Bone reabsorption
Plasma Ca
Plasma phosphate

Answer 35

PTH: decreased
Bone reabsorption: increased
Plasma Ca: increased
Plasma phosphate: decreased

Question 36

What happens in rickets disease?

Answer 36

Insufficient Vitamin D, Ca, and PO4 to mineralized growing bone.