Shricker Study Guide

Question 1

What is the mineral composition of bone?

Answer 1

Hydroxyapatite

Question 2

What is the primary protein component of bone?

Answer 2

collagen

Question 3

What is the major calcium reserve in our body?

Answer 3

bone

Question 4

How do remodeling cycle and serum calcium levels affect one another?

Answer 4

decrease bone mass causes increase in remodeling = increase serum calcium

Question 5

Where is calcium found other than bone?

Answer 5

teeth and bound to albumin

Question 6

How is calcium distribute in serum?

Answer 6

ionized calcium = 50% (biologically active)
protein bound calcium (bound to albumin) = 40% (biologically inactive)
citrate or phosphate bound calcium = 10%

Question 7

Which type of bound calcium is biological inactive? active?

Answer 7

• protein bound

- ionized calcium

Question 8

What factors regulate the bone remodeling cycle?

Answer 8

Serum calcium, hormones, cytokines
- high serum calcium = inhibits resorption
- hormones (PTH, prolactin, prostaglandin, cytokines = promote bone resorption
estrogens and calcitonin = inhibit bone resorption)

Question 9

What cells are involved in bone resorption

Answer 9

mesenchymal cells -> preosteoblast -> osteoblasts -> osteocyte
hematopoietic stem cells -> monocyte/macrophage -> preosteoclast -> osteoclasts

Question 10

How are osteoclasts regulated?

Answer 10

RANKL bind RANK on osteoclasts to trigger osteoclasts to resorb bone
- estrogen activates OPG which inhibits RANKL from binding RANK

Question 11

How do osteoblasts regulate osteoclasts?

Answer 11

PTH indirectly stimulates osteoclasts
PTH binds osteoblasts signaling them to up regulate expression of RANKL
Osteoblast RANKL contacts osteoclast RANK and osteoclast precursors differentiate into mature osteoclasts

Question 12

What are the major consequences of increased PTH?

Answer 12

increases osteoclast activity which increases serum calcium and decreases serum phosphate
- increases calcium reabsorption in kidneys and small intestine

Question 13

What regulates PTH production?

Answer 13

stimulated by low plasma calcium levels

Question 14

What are consequences of increased vitamin D production?

Answer 14

increases serum calcium levels, gut absorbs calcium and increases bone resorption because of calcium intake from diet

Question 15

What regulates vitamin D production?

Answer 15

synthesized in skin from sunlight

• stored in liver, converted to active form in kidney
• 1-alpha hydrolase in the kidney is major point of vitamin D maturation and regulation

Question 16

What is the major cause of hypercalcemia (high calcium blood serum levels)?

Answer 16

Primary hyperparathyroidism, malignant disease, iatrogenic vitamin D

Question 17

What is the treatment for hypercalcemia?

Answer 17

primary hyperparathyroidism = surgery
malignant disease = Bisphosphonates which inhibit osteoclast activity
iatrogenic = vitamin D (3rd leading cause)

Question 18

How is hypercalcemia detected with intact PTH?

Answer 18

over expression of PTH overwhelms its half-life causing intact form rather than cleaved form for longer than normal, antibody detects

Question 19

how do antibodies detect intact PTH?

Answer 19

two antibodies are used to detect both “cleaved segments” to determine if they are intact

Question 20

What is the major cause of hypopcalcemia?

Answer 20

Damaged parathyroid gland

Question 21

How is hypocalcemia treated?

Answer 21

Hypoparathyroid = surgery
non parathyroid =
PTH resistance = administer magnesium

Question 22

What causes abnormal metabolism of vitamin D?

Answer 22

vitamin D deficiency, tissue resistance to vitamin D and from liver disease or renal failure

Question 23

Defects in HA formation due to vit D deficiency

Answer 23

osteomalacia (rickets cured by Cod liver oil)

Question 24

loss of mineral density with age, increase risk of fracture, rates of bone synthesis and resorption change

Answer 24

osteoporosis (treat with estrogens, bisphosphonates, calcitonin, PTH)

Question 25

Numerous osteoclasts and osteoblasts, increase in alkaline phosphatase, large misshapen dense and brittle bones

Answer 25

Pagets disease (treat with bisphosphonates and calcitonin)

Question 26

How does calcitonin affect serum calcium?

Answer 26

decreases serum calcium and increases Ca2+ in bone