Lecture 4

Question 1

considerations in lactose intolerance

Answer 1

• calcium intake: LI people have lower intake
• calcium content: common foods have lower calcium bioavailability
• milk intake: LI associated with low milk consumption and low bone mineral density

Question 2

osteoporosis

Answer 2

• skeletal disease characterized by low bone minderal density (BMD) and micro-architectural deterioration of bone tissue/structure
• increased risk fracture
• no symptoms: dont know until you fall
• dual X-ray absorptiometry (DXA/DEXA) most important determinant of bone strength and BMD: diagnoses osteopenia and osteoporosis

Question 3

calcium metabolism

Answer 3

• all calcium from diet
• 99% stored in bone, 1% in extracellular fluid
• conc in extracellular fluid is tightly regulated between 9-10.5 mg/dL (HOMEOSTATIC SET RANGE)

absorption: small intestine
reabsorption: kidney
resorption: bone (dissolving bone to release calcium into blood)

Question 4

Review of hormonal control maintaining calcium homeostasis

Answer 4

1. Parathyroid hormone (PTH): first response to low blood calcium
   - secreted by parathyroid gland
   - serves to INCREASE blood calcium by stimulating calcitriol and bone resorption
2. calcitriol: second response to low blood calcium
   - activate metabolite of vit D made in kidney
   - serves to INCREASE blood calcium by stimulating bone resorption and Ca absorption
3. calcitonin: response to high blood calcium
   - secreted by thyroid parafollicular cells
   - serves to DECREASE blood calcium by inhibiting bone resorption, improves bone density

Question 5

calcitriol

Answer 5

can influence many disease processes
- decreases adaptive immune system activation:
decreases B and T cell proliferation, inflammatory cytokines, etc
- stimulates antimicrobial protein secretion