LECTURE - Bone Mineral Metabolism

Question 1

requirements for bone metabolism

Answer 1

• adequate collage matrix + blood Ca and Phos

- bone alkaline phosphatase (ALP)

Question 2

consequences of problems in bone metabolism

Answer 2

disturbing cycle of regular bone metabolism

• increase in blood Ca and Phos
• release of collagen breakdown products

Question 3

PTH actions

Answer 3

• on bone: increases bone resorption
• on kidney: increases Ca reabsorption, stimulates Phos excretion, increases the synthesis of 1,25(OH)2D

overall:

• increase serum Ca
• decreases serum Phod

increase in serum phos also causes PTH release

Question 4

calcitonin

Answer 4

• released when serum Ca is high
• inhibits bone resorption
• increases kidney Ca excretion
• decreases serum Ca overall

Question 5

role of 1,25 (OH)2D

Answer 5

• intestine: increases absorption of dietary Ca and Phos
• parathyroid: decreases PTH synthesis

overall increases serum Ca and Phos

Question 6

hypocalcemia

Answer 6

serum calcium conctn below the reference interval
- may be associated w following symptoms:
> neuromuscular (involuntary contraction of muscles; numbness/tingling)
> altered mental status

Question 7

hypercalcemia

Answer 7

• serum Ca conctn above reference interval
• may be associated with:
  > stones: kidney stones, diuresis, dehydration
  > moans: altered mental status (whether increase or decrease in electrolytes)
  > groans: constipation, nausea, vomiting
  > bones: bone pain

Question 8

causes of hypercalcemia can be distinguished by measuring

Answer 8

serum PTH immunoassay

Question 9

vitamin D deficiency and inadequate Ca intake

Answer 9

• rickets in children
• osteomalacia in adults
  > bowing of extremities, short stature, bone pain, stress fractures

Question 10

calcium deficiency, inactive lifestyle, estrogen deficiency

Answer 10

• osteoporosis
  > compromised bone quantity and quality (porous bones)
  > increased fracture risk

Question 11

assessment of vitamin D status

Answer 11

• assessment and monitoring of bone disorders (rickets, osteomalacia, osteoporosis)
• monitoring patients w malabsorption, renal disease
• 2-OH vitamin D (inactive form) best measure of vit D status
  > major circulating form of vit D
  > longer half-life than 1,25(OH)2D