Vitamin D and analogues are core subjects for B.Pharm students, integrating pharmacology, biochemistry, and therapeutics. This introduction-rich MCQ set covers vitamin D metabolism, activation (CYP2R1, CYP27B1), vitamin D receptor (VDR) signaling, pharmacokinetics, and clinical applications of calcitriol, cholecalciferol, ergocalciferol, alfacalcidol, paricalcitol, and calcipotriol. Questions probe mechanisms of intestinal calcium absorption, renal and hepatic activation, monitoring (25-hydroxyvitamin D, calcium, PTH), drug interactions, indications (rickets, hypoparathyroidism, CKD, psoriasis), and toxicity (hypercalcemia). Designed for exam preparation and deeper conceptual understanding, these MCQs will strengthen prescribing rationale and safety awareness. ‘Now let’s test your knowledge with 30 MCQs on this topic.’
Q1. Which is the primary circulating form of vitamin D measured to assess vitamin D status?
- 1,25-dihydroxyvitamin D (calcitriol)
- 25-hydroxyvitamin D (calcifediol)
- 7-dehydrocholesterol
- Vitamin D binding protein (DBP)
Correct Answer: 25-hydroxyvitamin D (calcifediol)
Q2. What is the biologically active hormonal form of vitamin D that binds the VDR?
- Cholecalciferol (vitamin D3)
- Ergocalciferol (vitamin D2)
- 1,25-dihydroxyvitamin D3 (calcitriol)
- 25-hydroxyvitamin D (calcifediol)
Correct Answer: 1,25-dihydroxyvitamin D3 (calcitriol)
Q3. Which enzyme catalyzes the renal conversion of 25-hydroxyvitamin D to the active 1,25-dihydroxy form?
- CYP3A4
- CYP24A1
- CYP27B1 (1α-hydroxylase)
- CYP2R1
Correct Answer: CYP27B1 (1α-hydroxylase)
Q4. The vitamin D receptor (VDR) primarily exerts its effects by:
- Activating G-protein coupled receptor pathways
- Forming a heterodimer with retinoid X receptor (RXR) to regulate gene transcription
- Directly phosphorylating target proteins in the cytosol
- Blocking nuclear import of transcription factors
Correct Answer: Forming a heterodimer with retinoid X receptor (RXR) to regulate gene transcription
Q5. The major cutaneous precursor converted by UVB to vitamin D3 is:
- Cholesterol
- 7-dehydrocholesterol
- Ergosterol
- Lanosterol
Correct Answer: 7-dehydrocholesterol
Q6. Which statement correctly contrasts ergocalciferol (D2) and cholecalciferol (D3)?
- Ergocalciferol is human skin–derived and more potent than cholecalciferol
- Cholecalciferol is plant-derived and less effective at raising 25(OH)D
- Ergocalciferol (D2) is plant-derived and generally less potent than cholecalciferol (D3)
- Both have identical potency and pharmacokinetics in all clinical situations
Correct Answer: Ergocalciferol (D2) is plant-derived and generally less potent than cholecalciferol (D3)
Q7. Which vitamin D analogue is commonly used to manage secondary hyperparathyroidism in chronic kidney disease with reduced hypercalcemic risk?
- Calcitriol
- Paricalcitol
- Ergocalciferol
- Cholecalciferol
Correct Answer: Paricalcitol
Q8. Which synthetic vitamin D analogue is primarily used topically to treat psoriasis by modulating keratinocyte proliferation?
- Paricalcitol
- Calcipotriol (calcipotriene)
- Doxercalciferol
- Alfacalcidol
Correct Answer: Calcipotriol (calcipotriene)
Q9. The most consistent biochemical feature of vitamin D intoxication is:
- Hypocalcemia
- Hypercalcemia
- Elevated PTH
- Low serum phosphate
Correct Answer: Hypercalcemia
Q10. Which plasma protein is the main carrier for vitamin D metabolites in circulation?
- Albumin
- Transferrin
- Vitamin D binding protein (DBP)
- Alpha-1-acid glycoprotein
Correct Answer: Vitamin D binding protein (DBP)
Q11. CYP24A1 enzyme primarily functions to:
- Synthesize 25-hydroxyvitamin D in the liver
- Activate calcifediol to calcitriol
- Catabolize and inactivate vitamin D metabolites via 24-hydroxylation
- Transport vitamin D across membranes
Correct Answer: Catabolize and inactivate vitamin D metabolites via 24-hydroxylation
Q12. Which vitamin D analogue is advantageous in patients with renal failure because it bypasses the need for renal 1α-hydroxylation?
- Calcitriol
- Alfacalcidol (1α-hydroxyvitamin D3)
- Ergocalciferol
- Cholecalciferol
Correct Answer: Alfacalcidol (1α-hydroxyvitamin D3)
Q13. Vitamin D enhances intestinal calcium absorption mainly by upregulating which of the following proteins?
- Parathyroid hormone (PTH)
- TRPV6 and calbindin
- Renin and angiotensin
- Albumin and transferrin
Correct Answer: TRPV6 and calbindin
Q14. The best laboratory test to assess a patient’s overall vitamin D stores is:
- Serum calcium
- 1,25-dihydroxyvitamin D (calcitriol)
- 25-hydroxyvitamin D (25(OH)D)
- Urinary calcium excretion
Correct Answer: 25-hydroxyvitamin D (25(OH)D)
Q15. Which vitamin D metabolite has the longest plasma half-life and serves as a stable marker of stores?
- Calcitriol (1,25(OH)2D)
- Cholecalciferol (vitamin D3)
- 25-hydroxyvitamin D (25(OH)D)
- 7-dehydrocholesterol
Correct Answer: 25-hydroxyvitamin D (25(OH)D)
Q16. Which commonly used antiepileptic drug induces hepatic enzymes and can accelerate vitamin D catabolism leading to deficiency?
- Levetiracetam
- Phenytoin
- Gabapentin
- Lamotrigine
Correct Answer: Phenytoin
Q17. Calcitriol is directly indicated as therapy in which of the following conditions?
- Primary osteoporosis without hypocalcemia
- Hypoparathyroidism with hypocalcemia
- Acute bacterial osteomyelitis
- Vitamin C deficiency
Correct Answer: Hypoparathyroidism with hypocalcemia
Q18. UVB radiation that converts 7-dehydrocholesterol to previtamin D3 primarily lies within which wavelength range?
- 100–200 nm
- 290–315 nm
- 400–700 nm
- 200–250 nm
Correct Answer: 290–315 nm
Q19. Which vitamin D analogue was developed to minimize hypercalcemia while suppressing parathyroid hormone in CKD?
- Calcitriol
- Paricalcitol
- Cholecalciferol
- Ergocalciferol
Correct Answer: Paricalcitol
Q20. The principal hepatic 25-hydroxylase enzyme responsible for converting vitamin D to 25(OH)D is:
- CYP27B1
- CYP2R1
- CYP24A1
- CYP1A2
Correct Answer: CYP2R1
Q21. Topical calcipotriol treats psoriasis primarily by:
- Stimulating osteoclast-mediated bone resorption
- Inhibiting keratinocyte proliferation and promoting differentiation
- Blocking vitamin D receptor in immune cells
- Increasing systemic calcitriol levels
Correct Answer: Inhibiting keratinocyte proliferation and promoting differentiation
Q22. In vitamin D intoxication, serum parathyroid hormone (PTH) is expected to be:
- Elevated due to increased bone resorption
- Normal because of homeostatic mechanisms
- Suppressed due to hypercalcemia
- Variable without pattern
Correct Answer: Suppressed due to hypercalcemia
Q23. Which clinical condition is most likely to impair oral absorption of vitamin D and lead to deficiency?
- Pancreatic insufficiency and fat malabsorption
- Hyperthyroidism with increased bone turnover
- Renal tubular acidosis
- Isolated iron deficiency anemia
Correct Answer: Pancreatic insufficiency and fat malabsorption
Q24. Which analogue is a prodrug that requires 25-hydroxylation in the liver to form the active hormone and is useful in renal failure?
- Calcitriol
- Alfacalcidol
- Paricalcitol
- Cholecalciferol
Correct Answer: Alfacalcidol
Q25. Vitamin D receptor (VDR) expression in nonclassical target cells includes which of the following?
- Red blood cells only
- Immune cells (macrophages and T cells)
- Hair follicles exclusively
- Adipocytes only
Correct Answer: Immune cells (macrophages and T cells)
Q26. Which antimicrobial agent is known to induce hepatic enzymes and can increase vitamin D catabolism, risking deficiency?
- Azithromycin
- Rifampicin (rifampin)
- Amoxicillin
- Vancomycin
Correct Answer: Rifampicin (rifampin)
Q27. Vitamin D promotes bone resorption indirectly by increasing which osteoblastic mediator that activates osteoclasts?
- Osteoprotegerin (OPG)
- RANKL (receptor activator of nuclear factor κB ligand)
- Calcitonin
- Bone morphogenetic protein (BMP)
Correct Answer: RANKL (receptor activator of nuclear factor κB ligand)
Q28. Classic biochemical findings in nutritional rickets due to vitamin D deficiency include:
- Low 25(OH)D, low calcium, low phosphate, and elevated alkaline phosphatase
- High 25(OH)D, high calcium, low alkaline phosphatase
- Normal 25(OH)D with elevated calcitriol levels only
- Isolated hyperphosphatemia with normal calcium
Correct Answer: Low 25(OH)D, low calcium, low phosphate, and elevated alkaline phosphatase
Q29. When monitoring for vitamin D analogue toxicity, the most critical laboratory test to follow regularly is:
- Serum magnesium
- Serum calcium
- Serum albumin only
- Serum bilirubin
Correct Answer: Serum calcium
Q30. Which statement is correct regarding cholecalciferol (D3) compared with ergocalciferol (D2) in supplementation?
- Ergocalciferol consistently provides superior and longer-lasting increases in 25(OH)D
- Cholecalciferol (vitamin D3) is generally more effective than ergocalciferol (D2) at raising and maintaining 25(OH)D levels
- Both are identical in potency and clinical outcomes in all patients
- Cholecalciferol is always less bioavailable than ergocalciferol
Correct Answer: Cholecalciferol (vitamin D3) is generally more effective than ergocalciferol (D2) at raising and maintaining 25(OH)D levels
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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