Parathormone MCQs With Answer — A concise, focused review for B. Pharm students: Parathormone (PTH) is the primary regulator of calcium and phosphate metabolism, acting via PTH receptor-mediated signaling to influence bone resorption, renal reabsorption, and vitamin D activation. This set covers physiology, mechanism of action, pathophysiology of hyperparathyroidism and hypoparathyroidism, diagnostic markers, and therapeutic agents including PTH analogs and calcimimetics. Emphasis is on pharmacology, pharmacokinetics, clinical correlations, and exam-oriented facts to strengthen conceptual understanding and clinical application. Detailed questions probe signaling pathways, downstream effects on osteoclasts, medical management, dosing considerations, and adverse effects. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which of the following is the primary physiological stimulus for parathyroid hormone (PTH) secretion?
- Increase in serum phosphate
- Decrease in serum calcium
- Increase in serum magnesium
- Decrease in serum 1,25-dihydroxyvitamin D
Correct Answer: Decrease in serum calcium
Q2. PTH exerts its effects on target cells primarily through which intracellular signaling pathway?
- Phospholipase C – IP3/DAG pathway
- cAMP – protein kinase A pathway
- TGF-beta / Smad pathway
- JAK-STAT pathway
Correct Answer: cAMP – protein kinase A pathway
Q3. In the kidney, PTH increases reabsorption of calcium in which segment of the nephron?
- Proximal convoluted tubule
- Thick ascending limb of Henle
- Distal convoluted tubule
- Collecting duct
Correct Answer: Distal convoluted tubule
Q4. Which enzyme’s activity is increased by PTH in the kidney to enhance active vitamin D (1,25-dihydroxyvitamin D) synthesis?
- 24-hydroxylase
- 25-hydroxylase
- 1-alpha-hydroxylase
- 7-dehydrocholesterol reductase
Correct Answer: 1-alpha-hydroxylase
Q5. Chronic elevation of PTH most characteristically causes which change in bone?
- Increased bone formation without resorption
- Net bone loss with increased osteoclastic activity
- Deposition of calcium phosphate crystals in cartilage
- Osteopetrosis due to decreased osteoclast function
Correct Answer: Net bone loss with increased osteoclastic activity
Q6. Teriparatide is a therapeutic agent related to PTH. Its approved clinical use is primarily for:
- Short-term treatment of hypercalcemia
- Long-term suppression of PTH in hyperparathyroidism
- Intermittent therapy to stimulate bone formation in osteoporosis
- Treatment of secondary hyperparathyroidism in CKD
Correct Answer: Intermittent therapy to stimulate bone formation in osteoporosis
Q7. The calcium-sensing receptor (CaSR) on parathyroid cells modulates PTH release. Activation of CaSR leads to:
- Increased PTH secretion
- No change in PTH secretion
- Decreased PTH secretion
- Increased synthesis of PTH-related peptide (PTHrP)
Correct Answer: Decreased PTH secretion
Q8. Cinacalcet is a drug used in secondary hyperparathyroidism. Its mechanism is best described as:
- Vitamin D receptor agonist
- Calcimimetic that activates CaSR
- PTH receptor antagonist
- Bisphosphonate that inhibits osteoclasts
Correct Answer: Calcimimetic that activates CaSR
Q9. Which laboratory pattern is most consistent with primary hyperparathyroidism?
- Low serum calcium, high PTH, high phosphate
- High serum calcium, high PTH, low phosphate
- High serum calcium, low PTH, high phosphate
- Low serum calcium, low PTH, low phosphate
Correct Answer: High serum calcium, high PTH, low phosphate
Q10. Pseudohypoparathyroidism is characterized by which abnormality?
- Excessive PTH production from adenoma
- End-organ resistance to PTH at receptor/Gs protein level
- Autoimmune destruction of parathyroid glands
- Vitamin D intoxication with suppressed PTH
Correct Answer: End-organ resistance to PTH at receptor/Gs protein level
Q11. Which of the following is a direct effect of PTH on osteoblasts that leads to increased osteoclast activity?
- Stimulation of osteoprotegerin synthesis
- Upregulation of RANKL expression
- Inhibition of RANKL and promotion of OPG
- Direct differentiation of osteoclast precursors via PTH receptor on osteoclasts
Correct Answer: Upregulation of RANKL expression
Q12. The half-life of endogenous PTH in circulation is approximately:
- Several hours
- 30–60 minutes
- 3–5 minutes
- 24–48 hours
Correct Answer: 3–5 minutes
Q13. Which condition is most likely to cause secondary hyperparathyroidism?
- Primary parathyroid adenoma
- Chronic kidney disease with hypocalcemia
- Excessive intake of vitamin D
- Hypermagnesemia
Correct Answer: Chronic kidney disease with hypocalcemia
Q14. Which biochemical marker increases as a consequence of high bone turnover induced by excess PTH?
- Serum albumin
- Alkaline phosphatase (bone-specific)
- C-reactive protein
- Serum creatinine
Correct Answer: Alkaline phosphatase (bone-specific)
Q15. In acute severe hypocalcemia due to hypoparathyroidism, the immediate IV treatment of choice is:
- IV magnesium sulfate
- IV calcium gluconate
- IV phosphate solution
- IV calcitonin
Correct Answer: IV calcium gluconate
Q16. Which PTH-related medication carries a boxed warning regarding potential risk of osteosarcoma in animal studies?
- Cinacalcet
- Teriparatide
- Calcitriol
- Denosumab
Correct Answer: Teriparatide
Q17. Which statement about intermittent versus continuous PTH exposure is correct?
- Both intermittent and continuous PTH lead to net bone formation
- Intermittent PTH promotes bone formation; continuous PTH causes bone resorption
- Continuous PTH promotes bone formation; intermittent PTH causes bone loss
- Neither pattern affects bone turnover
Correct Answer: Intermittent PTH promotes bone formation; continuous PTH causes bone resorption
Q18. Measurement of urinary cyclic AMP (cAMP) following PTH action is useful because:
- Urinary cAMP decreases with PTH activity
- PTH stimulates renal production of cAMP reflecting receptor activation
- cAMP is directly secreted by parathyroid glands into urine
- Urinary cAMP correlates with vitamin D levels only
Correct Answer: PTH stimulates renal production of cAMP reflecting receptor activation
Q19. Which genetic syndrome is associated with parathyroid adenomas and hyperparathyroidism?
- MEN1 (Multiple Endocrine Neoplasia type 1)
- Marfan syndrome
- Turner syndrome
- Cystic fibrosis
Correct Answer: MEN1 (Multiple Endocrine Neoplasia type 1)
Q20. Hypomagnesemia affects PTH secretion and action by:
- Stimulating excessive PTH release leading to hypercalcemia
- Inhibiting PTH release and causing resistance to PTH actions
- Having no effect on PTH physiology
- Increasing PTH receptor density on target cells
Correct Answer: Inhibiting PTH release and causing resistance to PTH actions
Q21. Which laboratory finding helps distinguish familial hypocalciuric hypercalcemia (FHH) from primary hyperparathyroidism?
- High urinary calcium excretion in FHH
- Low urinary calcium excretion in FHH
- Elevated PTH in primary hyperparathyroidism only
- Low serum phosphate in FHH only
Correct Answer: Low urinary calcium excretion in FHH
Q22. Which therapeutic agent directly mimics PTH receptor activation to treat hypoparathyroidism?
- Teriparatide (PTH 1-34)
- Cinacalcet
- Alendronate
- Calcitonin
Correct Answer: Teriparatide (PTH 1-34)
Q23. Secondary hyperparathyroidism due to chronic renal failure features which combination?
- Low PTH, high 1,25(OH)2D, hypocalcemia
- High PTH, low 1,25(OH)2D, hypocalcemia
- High PTH, high 1,25(OH)2D, hypercalcemia
- Low PTH, low phosphate, hypercalcemia
Correct Answer: High PTH, low 1,25(OH)2D, hypocalcemia
Q24. Which of the following best describes the pharmacokinetic property of endogenous PTH relevant for therapeutic design?
- Long circulating half-life enabling weekly dosing
- Short plasma half-life necessitating parenteral or intermittent administration for analogs
- Excellent oral bioavailability
- Extensive hepatic metabolism allowing oral dosing
Correct Answer: Short plasma half-life necessitating parenteral or intermittent administration for analogs
Q25. In primary hyperparathyroidism, which imaging modality is commonly used preoperatively to localize adenomas?
- Chest X-ray
- 99mTc-sestamibi parathyroid scan
- Abdominal ultrasound
- DEXA scan
Correct Answer: 99mTc-sestamibi parathyroid scan
Q26. Which of the following is NOT a direct effect of elevated PTH?
- Increased renal phosphate excretion
- Enhanced intestinal calcium absorption independent of vitamin D
- Stimulation of osteoclast-mediated bone resorption (indirect)
- Activation of renal 1-alpha-hydroxylase
Correct Answer: Enhanced intestinal calcium absorption independent of vitamin D
Q27. A patient with hyperparathyroidism is most likely to present clinically with which triad historically described as “stones, bones, and groans”?
- Kidney stones, bone pain/fragility, gastrointestinal symptoms
- Urinary incontinence, muscle hypertrophy, cough
- Weight gain, cold intolerance, constipation due to hypothyroidism
- Fever, rash, joint swelling due to autoimmune disease
Correct Answer: Kidney stones, bone pain/fragility, gastrointestinal symptoms
Q28. Which factor most directly suppresses PTH gene expression in parathyroid cells?
- Low extracellular calcium
- High extracellular calcium via CaSR activation
- High PTH-related peptide (PTHrP) levels
- Low 1,25-dihydroxyvitamin D
Correct Answer: High extracellular calcium via CaSR activation
Q29. During pharmacologic treatment of osteoporosis with teriparatide, monitoring is necessary for which laboratory parameter due to risk of elevation?
- Serum potassium
- Serum calcium
- Serum sodium
- Serum phosphate only
Correct Answer: Serum calcium
Q30. Which statement about PTH-related peptide (PTHrP) is correct?
- PTHrP is only produced by parathyroid glands and has identical functions to PTH
- PTHrP is implicated in humoral hypercalcemia of malignancy and can mimic some PTH effects
- PTHrP decreases bone resorption and reduces calcium levels
- PTHrP administration is the standard therapy for hypoparathyroidism
Correct Answer: PTHrP is implicated in humoral hypercalcemia of malignancy and can mimic some PTH effects
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