Mineral Homeostasis and Bone Turnover

Question 1

What two specialized cells are responsible for skeleton remodeling?

Answer 1

Osteoblasts and osteoclasts

Question 2

Bone remodeling usually occurs in response to what two factors?

Answer 2

Mechanical forces

Endocrine and paracrine factors

Question 3

Bone is ___% organic component and ___% inorganic component

Answer 3

25%, 75%

Question 4

What is the main inorganic compound of bone?

Answer 4

Hydroxyapatite

Question 5

What are the main organic components of bone?

Answer 5

Cells and osteoid

Question 6

What percent of body calcium is stored in the skeleton and in what form?

Answer 6

99%, hydroxyapatite

Question 7

What vitamin helps enhance absorption of calcium in the body?

Answer 7

Vitamin D

Question 8

Inherited deficiency of RANKL or RANK causes a form of what?

Answer 8

Osteopetrosis

Question 9

Inherited deficiency of OPG causes increased bone resorption and what?

Answer 9

Osteoporosis

Question 10

Osteoclasts are responsible for what process?

Answer 10

Bone resorption

Question 11

Osteoblasts are responsible for what process?

Answer 11

Bone formation

Question 12

What is the most numerous bone cell type?

Answer 12

Osteocytes

Question 13

What is the function of sclerostin?

Answer 13

It is a protein that inhibits bone formation

Question 14

Which three hormones mainly mediate calcium and phosphate homeostasis?

Answer 14

parathyroid hormone (PTH), vitamin D, and FGF-23

Question 15

Vitamin D refers to which two compounds?

Answer 15

Cholecalciferol (D3) and ergocalciferol (D2)

Question 16

True or false: Vitamin D3 is produced endogenously in the parathyroid gland

Answer 16

False. In the skin

Question 17

Why is Vitamin D considered a hormone?

Answer 17

It travels from the skin where it is produced in the blood to effect responses in distant target tissues

Question 18

Why or how is sunlight an important source of Vitamin D?

Answer 18

Vitamin D production in the skin is produced via exposure to sunlight

Question 19

Antiresorptive agents MOA

Answer 19

Antiresorptive agents prevent or arrest bone loss by suppressing osteoclastic bone resorption

Question 20

Hormone Replacement Therapy antiresorptive MOA

Answer 20

Estrogens reduce bone resorption by suppressing the transcription of genes coding for RANKL and cytokines such as IL-6

Question 21

Adverse effects of Hormone Replacement Therapy

Answer 21

Vaginal bleeding
Breast tenderness
Increased risk of venous thromboembolism
Increased long-term risk of breast cancer

Question 22

What are the different classes of antiresorptive agents?

Answer 22

Hormone Replacement Therapy
Selective Estrogen Receptor Modulators
Bisphosphonates
RANKL Antagonists
Calcitonin

Question 23

What is the most commonly used class of antiresorptive drugs?

Answer 23

Bisphosphonates

Question 24

Bisphosphonates are analogues of pyrophosphates in which the readily _____ P-O-P bond is replaces by a ______ P-C-P bond

Answer 24

hydrolysable, nonhydrolyzable

Question 25

5 common examples of bisphosphonates

Answer 25

``` Alendronate Risedronate Ibandronate Pamidronate Zoledronate ```

Question 26

What characteristic of bisphosphonates increases their antiresorptive activity?

Answer 26

Nitrogen-containing amino, pyridine, or imidazole moiety in the side chain

Question 27

Bone anabolic agents MOA

Answer 27

Increase bone mass and bone strength, not just prevent its loss

Question 28

What was the first bone anabolic agent?

Answer 28

Fluoride

Question 29

Fluoride MOA

Answer 29

Converts hydroxyapatite to fluoroapatite, which is denser and more brittle

Question 30

Native PTH contains how many amino acids?

Answer 30

84 AAs

Question 31

Is PTH an antiresorptive agent or a bone anabolic agent?

Answer 31

Bone anabolic agent

Question 32

What three classes of drugs are used to treat secondary hyperparathyroidism in CKD?

Answer 32

Oral phosphate binders Calcitriol and its analogues Calcimimetics

Question 33

What are the three active vitamin D congeners approved for treatment of secondary hyperparathyroidism?

Answer 33

Calcitriol- dihydroxylated form of vitamin D3 Paricalcitol- synthetic analogue of vitamin D Doxercalciferol- 1α-hydroxylated form of vitamin D2

Question 34

Which was the first approved calcimimetic drug? What is its MOA?

Answer 34

Cinacalcet. Binds to the transmembrane region of the calcium-sensing receptor and thereby modulates receptor activity by increasing its sensitivity to calcium