CALCIUM HOMEOSTASIS
1. Calcium is the ___________most common element of human body?
a. 4th
b. 1st
c. 3rd
d. 5th*
2. Calcium has important role in following body function EXCEPT?
a. Muscle contraction
b. Coagulation
c. Vision*
d. Bone metabolism
3. The concentration of ionized calcium in human body is about?
a. 20 %
b. 70 %
c. 50 %*
d. 10 %
4. Two hormones primarily responsible for calcium homeostasis are?
a. PTH & Vitamin D*
b. Vitamin D & Insulin
c. PTH & TFT
d. Insulin & cortisol
5. Following are the role of PTH in response to low calcium in serum EXCEPT?
a. Increased reabsorption of Phos*
b. Increased mobilization of Ca from bone
c. Increased kidney conversion of 25-OH to 1,25 diOH- Vitamin D
d. Increased kidney reabsorption of Ca
6. Which of the following statement is not true regarding 1 ,25 -diOH - D 3 calcium
regulation?
a. upregulates Ca mobilization from bone
b. Increase Ca absorption from intestine
c. Increase Phosphorous absorption from intestine
d. Increase excretion of Ca from kidney*
7. Which of the following organ involved in conversion of 25-OH vitamin D to 1,25
diOH- Vitamin D (active form)
a. Liver
b. Heart
c. Kidney*
d. Skin
8. Following are the non-parathyroid causes of Hypocalcemia EXCEPT?
a. Vitamin D deficiency
b. Malabsorption
c. Renal Disease
d. Heart Disease*
9. Considering Bone Remodeling Regulation which of the following hormones has net
osteoclastic impact on bone and result in bone loss?
a. Cortisol*
b. Testosterone
c. Calcitonin
d. Estrogen
10. Below 4 g/dL: for every 1 g/dL albumin decrease, Ca decreases by?
a. 0.8 mg/dL*
b. 1.0 mg/dL
c. 1.5 mg/dL
d. 2.5 mg/dL
11. Calcium
A: crosses the brush border of intestinal epithelium via a Na+/Ca++ exchanger
B: 50 000 mmol /day exchanges between bone and plasma
C: 85% is stored in bone
D: is more plasma-protein-bound at higher pH *
E: is the most important ion for Gas exchange
12. Phosphorus
A: 85-90% is in the skeleton *
B: 85-90% of daily intake is excreted in urine
C: homeostasis is independent of vitamin D
D: intestinal absorption is by diffusion down a concentration gradient
E: is not in equilibrium with Calcium and Magnesium
13. PTH (Parathyroid hormone) increases
A: osteoblast activity in the short term
B: reabsorption of Ca++ in the distal tubules *
C: reabsorption of urinary phosphate in the distal tubules
D: serum albumin
E: serum phosphorus levels
14. Regarding calcium in the kidney:
A: absorption in the distal tubule is variable *
B: is reabsorbed in the collecting duct
C: is secreted in the ascending limb of the loop of Henle
D: 98% is reabsorbed in the proximal tubule
E: 99% reabsorbed in collecting tubules
15. When serum calcium (Ca++) is high
A: activity of renal 1 alpha hydroxylase is inhibited *
B: expression of intestinal Calbindin-D is increased
C: PTH secretion is increased
D: 24, 25-dihydroxycholecalciferol production decreases
E: Thyroid hormone is increased
16. Calcitonin
A: inhibits bone resorption *
B: inhibits urinary excretion of calcium
C: is deficient in Zollinger Ellison syndrome
D: is produced in the parathyroid glands
E: increases Calcium
17. Glucocorticoids
A: can lead to hypercalcaemia
B: increase intestinal absorption of calcium and phosphate
C: inhibit protein synthesis in osteoblasts *
D: suppress PTH secretion
E: is good for bones
18. Trabecular bone
A: has a low surface to volume ratio
B: is supplied with nutrients via Haversian canals
C: makes up 80% of bone in adults
D: receives nutrients via diffusion from extracellular fluid *
E: is strong in osteoarthritis
19. Osteoclasts
A: are relatively inactive in children
B: attach to bone via integrins *
C: dissolve hydroxyapatite using alkaline secretions
D: increase activity in response to growth factors that act on fibroblasts
E: are responsible for making new bone
20. Vitamin D3
A: has limited first pass metabolism
B: has little absorption from the gastrointestinal tract
C: is bound to albumin in plasma
D: is produced by the action of sunlight on 7-dehydrocholesterol *
E: is vital for absorption if Iron
21. Bone remodeling is regulated locally by:
a. Macrophage colony stimulating factor (m-CSF)
b. Receptor activator of nuclear factor kappa B ligand (RANKL)
c. Osteoprotegrin (OPG)
d. All of above *
e. Only a and b
22. Which enzyme activity increases when osteoblasts begin making new bone?
a. C-terminal propeptide of type I procollagen
b. N-terminal propeptide of type I procollagen
c. Bone gamma carboxyglutamic acid protein
d. Bone-specific alkaline phosphatase *
e. Osteocalcin
23. Disadvantage of TRAP includes
a. failure to distinguish osteoclastic TRAP from other TRAPs *
b. cannot distinguish between osteoclast and osteoblast
c. Commercially unavailable
d. Too expensive
e. Difficult to analyze
24. Defective mineralization of osteoid in bone leads to
a. Osteoporosis
b. Osteomalacia *
c. Piget’s disease
d. Rickets
e. Acromegaly
25. Best time for measuring degradation products of bone remodeling in urine is
a. Early in morning *
b. Late at night
c. 06 hour sample
d. 12 hour sample
e. 18 hour sample
26. “Adjusted” Calcium for albumin concentration:
a. Adj Ca = Total Ca (mg/dL) - 0.8(4 – albumin[g/dL])
b. Adj Ca = Total Ca (mg/dL) + 0.8(4 – albumin[g/dL]) *
c. Adj Ca = Total Ca (mg/dL) + 0.8(2 – albumin[g/dL])
d. Adj Ca = Total Ca (mg/dL) - 0.8(2 – albumin[g/dL])
e. Adj Ca = Total Ca (mg/dL) + 0.8(4 – albumin[kg/dL])
27. Which statement is not true about ionized calcium?
a. Better reflects Ca metabolism and status
b. Biologically active and tightly regulated
c. Measured by ISE, generally whole blood sample
d. Measured in heparinized plasma or serum *
e. None of above
28. Which statement is true about PTH?
a. PTH is sometimes reported with Ca level
b. PTH is not stable at room temperature in EDTA
c. Useful for differential diagnosis of hypercalcemia and hypocalcemia *
d. Radioactivity is used for intact PTH
e. All of above
29. Main circulating form of Vit D is
a. 25-OH-D *
b. 27-OH-D
c. 1,25-diOH-D
d. 1,27-diOH-D
e. 1,25-diH-D
30. Vit D is deficient, when its level is
a. < 20 ng/mL *
b. 20 – 29 ng/mL
c. 30 – 80 ng/mL
d. > 80 ng/mL
e. 90 ng/mL
