Ch 75 Calcium and Bone Mineralization

Question 1

Calcium is critical to the function of the (4).

Answer 1

skeletal, nervous, muscular, and cardiovascular systems

Question 2

More than __ of calcium in the body is present in bone.

Answer 2

98%

Question 3

Bone undergoes continuous remodeling, a process in which __.

Answer 3

osteoclasts resorb old bone and osteoblasts lay down new bone.

Question 4

The body maintains calcium levels by (3).

Answer 4

adjusting the rates of calcium resorption from bone, calcium absorption from the intestine, and calcium excretion by the kidney.

These processes are regulated by parathyroid hormone (PTH), vitamin D, and calcitonin.

Question 5

PTH elevates serum calcium by (3).

Answer 5

promoting resorption of calcium from bone, enhancing renal tubular resorption of calcium, and activating vitamin D, which then promotes absorption of calcium from the intestine.

Question 6

Like PTH, vitamin D increases serum calcium by increasing (3).

Answer 6

calcium resorption from bone, decreasing calcium excretion by the kidney, and increasing calcium absorption from the intestine.

Question 7

__ lowers calcium levels by inhibiting calcium resorption from bone and increasing calcium excretion by the kidney.

Answer 7

Calcitonin

Question 8

The RDA for calcium is highest for __.

Answer 8

adolescents ages 9 to 18 (1300 mg/day).

Women over the age of 50 and all people over the age of 70 also need relatively high amounts (1200 mg/day).

Question 9

If the RDA cannot be met with diet alone, __ can be taken to make up the difference.

Answer 9

calcium supplements

However, be aware that too much supplemental calcium increases the risk of vascular calcification, myocardial infarction, and stroke.

Question 10

The various calcium salts used for therapy differ widely in their __.

Answer 10

percentage of calcium

Question 11

Vitamin D is obtained through (2).

Answer 11

the diet and by exposure to sunlight.

Question 12

__ causes rickets in children and osteomalacia in adults. Deficiency may also contribute to certain autoimmune disorders and cancers, although convincing evidence is lacking.

Answer 12

Vitamin D deficiency

Question 13

__ has the same metabolic effects as human calcitonin, but has a longer half-life and greater milligram potency.

Answer 13

Calcitonin-salmon

Question 14

Calcitonin-salmon

Answer 14

is used primarily for osteoporosis.

Benefits derive from inhibiting bone resorption by osteoclasts.

Question 15

Alendronate, our prototype for the bisphosphonates, has four approved indications:

Answer 15

prevention and treatment of osteoporosis in postmenopausal women,
treatment of osteoporosis in men,
treatment of Paget’s disease of bone in men and women,
and treatment of glucocorticoid-induced osteoporosis in men and women.

Question 16

Bioavailability of __ is very low in the absence of food and essentially zero in the presence of food.

Answer 16

alendronate

Accordingly, nothing should be eaten for at least 30 minutes after taking the drug.

Question 17

Following absorption, alendronate undergoes __.

Answer 17

incorporation into bone, where it can remain for decades.

Question 18

Alendronate suppresses __.

Answer 18

bone resorption by decreasing both the number and activity of osteoclasts

Question 19

Alendronate can cause severe __ if it stays in contact with the esophageal mucosa.

Answer 19

esophagitis

Accordingly, patients should take the drug with a full glass of water and then remain upright for at least 30 minutes.

Question 20

Rarely, alendronate has been associated with (4).

Answer 20

musculoskeletal pain,
ocular inflammation,
osteonecrosis of the jaw, and
atypical fractures of the femur.

Question 21

__ increases BMD and reduces fracture risk

Answer 21

Estrogen

Question 22

In the past, __ was considered a treatment of choice for the prevention and treatment of postmenopausal osteoporosis.

Answer 22

estrogen

Today, however, there is strong evidence that benefits in osteoporosis do not outweigh the risks (breast cancer, myocardial infarction, stroke, cholecystitis).

Question 23

Raloxifene belongs to the family of __.

Answer 23

SERMs, drugs that are estrogenic in some tissues and antiestrogenic in others.

Question 24

Raloxifene

Answer 24

mimics the effects of estrogen on bone, lipid metabolism, and blood clotting, and blocks the effects of estrogen in the breast and endometrium.

Question 25

Raloxifene is indicated for preventing and treating __.

Answer 25

postmenopausal osteoporosis and for reducing the risk of breast cancer in postmenopausal women

Question 26

Raloxifene can cause (3).

Answer 26

DVT, PE, and fetal harm.

Question 27

Teriparatide is the first and only drug for osteoporosis that works by __.

Answer 27

increasing bone formation.

All the others decrease bone resorption.

Question 28

Teriparatide may increase the risk of __.

Answer 28

bone cancer

Question 29

Denosumab is a first-in-class RANKL inhibitor indicated for:

Answer 29

postmenopausal osteoporosis and prevention of skeletal related events in patients with bone metastases from solid tumors.

Question 30

By inhibiting RANKL, denosumab prevents RANKL from activating RANK receptors and thereby reduces the __..

Answer 30

formation and function of osteoclasts

Question 31

Denosumab has four serious side effects:

Answer 31

hypocalcemia, infections, skin reactions, and ONJ.

Question 32

Osteoporosis is characterized by __.

Answer 32

low bone mass and increased bone fragility, which renders patients vulnerable to fractures from minor trauma

Question 33

The most common sites of osteoporotic fractures are

(3).

Answer 33

the vertebrae (spine), 
distal forearm (wrist), and 
femoral neck (hip)

Question 34

Osteoporosis occurs mainly in __.

Answer 34

older adults.

After age 50 years, men and women experience aging-related bone loss that is slow but relentless.

In addition, women experience several years of accelerated bone loss following menopause.

In both cases, bone is lost because bone resorption by osteoclasts outpaces bone deposition by osteoblasts.

Question 35

To maximize bone strength, and thereby minimize the risk of osteoporosis, we all need to:

Answer 35

(1) ensure lifelong sufficiency of calcium and vitamin D and (2) adopt lifestyle measures that promote bone health: regular weight-bearing exercise and avoidance of smoking and excessive alcohol.

Question 36

Osteoporosis is diagnosed by measuring __.

Answer 36

BMD, which is done most commonly using dual-energy x-ray absorptiometry (DEXA).

Question 37

The World Health Organization’s diagnostic criterion for osteoporosis is __.

Answer 37

BMD that is more than 2.5 standard deviations below the mean BMD for young adults

Question 38

The objective of osteoporosis therapy is to __.

Answer 38

reduce fractures

Question 39

__ is based on BMD and other factors, including age, use of glucocorticoids, and a personal or family history of fractures.

Answer 39

Fracture risk (which can be calculated using the FRAX
tool developed by the WHO)

Question 40

With currently available drugs, we are more able to __.

Answer 40

prevent bone loss (using antiresorptive agents) than to rebuild bone that is already gone (using bone-forming agents).

Question 41

Antiresorptive drugs—estrogen, raloxifene, bisphosphonates (e.g., alendronate), and calcitonin—___.

Answer 41

decrease bone loss by inhibiting the activity of osteoclasts