Structure and functions of parathyroid gland MCQs With Answer

Introduction: The Structure and functions of parathyroid gland MCQs With Answer provide B. Pharm students a focused review of parathyroid anatomy, histology, hormone synthesis, and physiological roles in calcium and phosphate homeostasis. This concise, exam-oriented guide covers parathyroid hormone (PTH) regulation, calcium-sensing receptor mechanisms, clinical disorders like hyperparathyroidism and hypoparathyroidism, diagnostic lab values, and pharmacological interventions. Emphasis on molecular pathways (PTH, PTHrP, RANKL), vitamin D interaction, and surgical considerations helps bridge basic science with therapeutics. Ideal for revision and competitive exams, these questions strengthen understanding and clinical reasoning. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which cell type is the principal source of parathyroid hormone (PTH) in the parathyroid gland?

• Oxyphil cells
• Chief (principal) cells
• Follicular cells
• Golgi cells

Correct Answer: Chief (principal) cells

Q2. The main physiological stimulus for PTH secretion is:

• High serum phosphate
• High serum calcium
• Low serum calcium
• High 1,25(OH)2 vitamin D

Correct Answer: Low serum calcium

Q3. Which receptor on parathyroid cells senses extracellular calcium levels?

• Vitamin D receptor (VDR)
• Calcium-sensing receptor (CaSR)
• PTH receptor type 1 (PTH1R)
• RANK receptor

Correct Answer: Calcium-sensing receptor (CaSR)

Q4. PTH increases serum calcium primarily by which of the following actions on bone?

• Directly stimulating osteoblast mineralization
• Increasing osteoclast activity indirectly via RANKL expression
• Inhibiting osteoclast formation
• Promoting bone formation through IGF-1

Correct Answer: Increasing osteoclast activity indirectly via RANKL expression

Q5. In the kidney, PTH promotes which of the following effects?

• Decreases calcium reabsorption in the distal tubule
• Increases phosphate reabsorption in the proximal tubule
• Increases 1α-hydroxylase activity to produce active vitamin D
• Inhibits bicarbonate reabsorption in the collecting duct

Correct Answer: Increases 1α-hydroxylase activity to produce active vitamin D

Q6. Which of the following describes the effect of PTH on renal phosphate handling?

• PTH increases proximal tubular phosphate reabsorption
• PTH decreases proximal tubular phosphate reabsorption
• PTH has no effect on phosphate handling
• PTH increases distal tubular phosphate secretion

Correct Answer: PTH decreases proximal tubular phosphate reabsorption

Q7. Which embryologic origin gives rise to the inferior parathyroid glands?

• Third pharyngeal pouch
• Second pharyngeal pouch
• Fourth pharyngeal pouch
• First pharyngeal pouch

Correct Answer: Third pharyngeal pouch

Q8. Normal intact PTH assay values are typically reported in which units?

• ng/mL
• pg/mL
• mmol/L
• mEq/L

Correct Answer: pg/mL

Q9. Which of the following is a hallmark biochemical finding in primary hyperparathyroidism?

• Low serum calcium, high PTH
• High serum calcium, high PTH
• High serum calcium, low PTH
• Low serum calcium, low PTH

Correct Answer: High serum calcium, high PTH

Q10. Which genetic syndrome is commonly associated with parathyroid adenomas and endocrine tumors?

• Down syndrome
• Multiple endocrine neoplasia type 1 (MEN1)
• Marfan syndrome
• Turner syndrome

Correct Answer: Multiple endocrine neoplasia type 1 (MEN1)

Q11. Oxyphil cells in the parathyroid are characterized by:

• High secretory granules containing PTH
• Abundant mitochondria and eosinophilic cytoplasm
• Basophilic cytoplasm and zymogen granules
• Primary role in phosphate handling

Correct Answer: Abundant mitochondria and eosinophilic cytoplasm

Q12. Which second messenger pathway is primarily activated by PTH binding to PTH1R in bone and kidney?

• cAMP/PKA pathway
• IP3/DAG pathway exclusively
• JAK/STAT pathway
• Notch signaling pathway

Correct Answer: cAMP/PKA pathway

Q13. PTH-related peptide (PTHrP) shares which property with PTH?

• Identical amino acid sequence throughout
• Can activate PTH1R and mimic PTH effects on bone and kidney
• Is produced only by the parathyroid gland
• Decreases serum calcium levels

Correct Answer: Can activate PTH1R and mimic PTH effects on bone and kidney

Q14. The most common cause of secondary hyperparathyroidism worldwide is:

• Primary parathyroid adenoma
• Chronic kidney disease with phosphate retention
• Excessive vitamin D intake
• Thyroid carcinoma

Correct Answer: Chronic kidney disease with phosphate retention

Q15. Which imaging modality is most commonly used preoperatively to localize a parathyroid adenoma?

• Chest X-ray
• Sestamibi scan (99mTc-sestamibi) with SPECT
• Abdominal ultrasound

Correct Answer: Sestamibi scan (99mTc-sestamibi) with SPECT

Q16. Pseudohypoparathyroidism is characterized by:

• Elevated PTH with hypocalcemia due to end-organ resistance to PTH
• Low PTH due to parathyroid destruction
• Excessive PTH secretion from a parathyroid adenoma
• High calcium despite low PTH

Correct Answer: Elevated PTH with hypocalcemia due to end-organ resistance to PTH

Q17. Which molecule is upregulated in osteoblasts by PTH to stimulate osteoclastogenesis?

• Osteoprotegerin (OPG)
• RANKL (Receptor activator of nuclear factor κB ligand)
• Calcitonin
• Alkaline phosphatase inhibitor

Correct Answer: RANKL (Receptor activator of nuclear factor κB ligand)

Q18. A patient with tertiary hyperparathyroidism typically shows which pattern?

• Hypocalcemia due to permanent hypoparathyroidism
• Autonomous hypersecretion of PTH after prolonged secondary hyperparathyroidism
• Normal calcium with suppressed PTH
• Transient hypercalcemia resolving without treatment

Correct Answer: Autonomous hypersecretion of PTH after prolonged secondary hyperparathyroidism

Q19. Which pharmacologic agent is a calcimimetic that activates the CaSR to lower PTH secretion?

• Calcitriol
• Cinacalcet
• Alendronate
• Teriparatide

Correct Answer: Cinacalcet

Q20. The classic bone lesion seen in severe primary hyperparathyroidism is called:

• Osteopetrosis
• Brown tumor (osteitis fibrosa cystica)
• Paget disease of bone
• Osteomalacia

Correct Answer: Brown tumor (osteitis fibrosa cystica)

Q21. Which lab profile suggests hypoparathyroidism?

• High PTH, high calcium
• Low PTH, low calcium
• High PTH, low phosphate
• Low PTH, high calcium

Correct Answer: Low PTH, low calcium

Q22. Surgical removal of hyperfunctioning parathyroid tissue may lead to hungry bone syndrome characterized by:

• Postoperative hypercalcemia due to bone resorption
• Severe postoperative hypocalcemia from rapid bone remineralization
• Persistent hyperphosphatemia without calcium change
• No changes in calcium or phosphate

Correct Answer: Severe postoperative hypocalcemia from rapid bone remineralization

Q23. Which vitamin D metabolite is most active biologically and synergizes with PTH to increase calcium absorption?

• 25-hydroxyvitamin D (25(OH)D)
• 1,25-dihydroxyvitamin D (1,25(OH)2D, calcitriol)
• Vitamin D2 (ergocalciferol)
• Cholecalciferol (vitamin D3)

Correct Answer: 1,25-dihydroxyvitamin D (1,25(OH)2D, calcitriol)

Q24. The primary blood supply to the parathyroid glands typically arises from:

• Superior thyroid artery
• Inferior thyroid artery
• Thyrocervical trunk directly to each gland
• External carotid artery

Correct Answer: Inferior thyroid artery

Q25. Which histological feature helps differentiate parathyroid tissue from thyroid tissue?

• Presence of colloid-filled follicles
• Clusters of chief cells without follicles
• Follicular epithelial lining
• Lymphoid follicles with germinal centers

Correct Answer: Clusters of chief cells without follicles

Q26. Teriparatide, used to treat osteoporosis, is best described as:

• A PTH receptor antagonist
• A recombinant PTH (1-34) fragment with anabolic bone effects when given intermittently
• A bisphosphonate that inhibits osteoclasts
• An anti-RANKL monoclonal antibody

Correct Answer: A recombinant PTH (1-34) fragment with anabolic bone effects when given intermittently

Q27. In pregnancy, which change in calcium-PTH physiology commonly occurs?

• PTH levels always fall to zero
• Increased intestinal calcium absorption due to higher calcitriol, often with stable or slightly increased PTH
• Severe hyperparathyroidism is typical and requires no monitoring
• Calcitonin secretion ceases completely

Correct Answer: Increased intestinal calcium absorption due to higher calcitriol, often with stable or slightly increased PTH

Q28. Parathyroid hormone acts on which kidney segment to increase calcium reabsorption?

• Proximal convoluted tubule
• Loop of Henle
• Distal convoluted tubule
• Collecting duct

Correct Answer: Distal convoluted tubule

Q29. Which condition is most likely associated with low 25(OH)D and secondary hyperparathyroidism?

• Vitamin D intoxication
• Severe vitamin D deficiency due to malabsorption
• Primary hyperparathyroidism due to adenoma
• Familial hypocalciuric hypercalcemia

Correct Answer: Severe vitamin D deficiency due to malabsorption

Q30. Familial hypocalciuric hypercalcemia (FHH) is due to a mutation in which receptor?

• Vitamin D receptor (VDR)
• Calcium-sensing receptor (CaSR)
• PTH1R
• RANK

Correct Answer: Calcium-sensing receptor (CaSR)

Q31. Which biochemical test is most useful to distinguish primary hyperparathyroidism from familial hypocalciuric hypercalcemia?

• Serum magnesium concentration
• 24-hour urinary calcium excretion (urine calcium/creatinine clearance ratio)
• Thyroid function tests
• Serum alkaline phosphatase only

Correct Answer: 24-hour urinary calcium excretion (urine calcium/creatinine clearance ratio)

Q32. The molecular action of the calcium-sensing receptor (CaSR) in parathyroid cells is primarily linked to which intracellular pathway?

• cAMP increase leading to PTH release
• Gq-mediated IP3/DAG signaling decreasing PTH secretion
• Tyrosine kinase activation promoting PTH synthesis
• Direct nuclear receptor activation altering gene transcription

Correct Answer: Gq-mediated IP3/DAG signaling decreasing PTH secretion

Q33. After parathyroidectomy, which change in serum phosphate is expected in a patient with primary hyperparathyroidism?

• Serum phosphate remains low permanently
• Serum phosphate typically increases toward normal levels
• Serum phosphate falls further
• No change in phosphate concentration

Correct Answer: Serum phosphate typically increases toward normal levels

Q34. Which of the following is a common symptom of hypercalcemia due to hyperparathyroidism?

• Muscle cramps and tetany
• Polyuria, polydipsia, and constipation
• Weight gain and hyperpigmentation
• Night blindness

Correct Answer: Polyuria, polydipsia, and constipation

Q35. Primary hyperparathyroidism is most commonly caused by:

• Parathyroid carcinoma in most cases
• Single parathyroid adenoma
• Autoimmune destruction of parathyroid glands
• Metastatic thyroid cancer to parathyroid tissue

Correct Answer: Single parathyroid adenoma

Q36. Which lab finding helps identify bone turnover in hyperparathyroidism?

• Serum creatinine only
• Elevated alkaline phosphatase and urinary hydroxyproline
• Decreased ESR only
• Low serum phosphate exclusively

Correct Answer: Elevated alkaline phosphatase and urinary hydroxyproline

Q37. The parathyroid glands are typically located at which relation to the thyroid lobes?

• Within the anterior midline of the neck
• Posterior surface of the thyroid lobes near the junction of the upper and middle thirds
• Inside the thyroid follicles
• Along the carotid sheath

Correct Answer: Posterior surface of the thyroid lobes near the junction of the upper and middle thirds

Q38. Which of the following drugs can cause hypercalcemia by increasing bone resorption or calcium release?

• Thiazide diuretics
• Loop diuretics (e.g., furosemide)
• Calcitonin
• Bisphosphonates

Correct Answer: Thiazide diuretics

Q39. In the context of parathyroid pathology, a markedly elevated serum PTH level with very high calcium suggests which diagnosis?

• Primary hyperparathyroidism due to adenoma or carcinoma
• Vitamin D deficiency
• Hypoparathyroidism due to surgery
• Familial hypocalciuric hypercalcemia with low urinary calcium

Correct Answer: Primary hyperparathyroidism due to adenoma or carcinoma

Q40. Which therapeutic approach is recommended for asymptomatic mild primary hyperparathyroidism in a young B. Pharm student learning guidelines?

• Immediate parathyroidectomy for all cases
• Conservative monitoring vs surgical referral based on age, calcium level, bone density, and renal function
• Treatment with high-dose vitamin D only
• Lifetime cinacalcet without evaluation

Correct Answer: Conservative monitoring vs surgical referral based on age, calcium level, bone density, and renal function

Q41. The rapid intraoperative PTH assay helps surgeons by:

• Measuring calcium levels during surgery
• Confirming removal of hypersecreting parathyroid tissue by showing a rapid drop in PTH
• Detecting thyroid carcinoma margins
• Determining bone density in real time

Correct Answer: Confirming removal of hypersecreting parathyroid tissue by showing a rapid drop in PTH

Q42. Which of the following describes the typical appearance of a parathyroid adenoma on histology?

• Dominance of chief cells with reduced adipose tissue and a thin capsule
• Follicular architecture with colloid
• Lymphocytic infiltration with germinal centers
• Predominant adipose tissue with few chief cells

Correct Answer: Dominance of chief cells with reduced adipose tissue and a thin capsule

Q43. The mechanism by which PTH increases renal 1α-hydroxylase activity results in:

• Decreased production of calcitriol
• Increased conversion of 25(OH)D to 1,25(OH)2D enhancing intestinal calcium absorption
• Inhibition of intestinal calcium absorption
• Enhanced renal phosphate reabsorption exclusively

Correct Answer: Increased conversion of 25(OH)D to 1,25(OH)2D enhancing intestinal calcium absorption

Q44. Which laboratory pattern is typical of hungry bone syndrome post-parathyroidectomy?

• Hypercalcemia and hyperphosphatemia
• Hypocalcemia, hypophosphatemia, and low PTH
• Normal calcium with elevated PTH
• Severe hyperphosphatemia with low calcium

Correct Answer: Hypocalcemia, hypophosphatemia, and low PTH

Q45. Which parathyroid disorder is characterized by ectopic parathyroid tissue often located in the mediastinum?

• Parathyroid hyperplasia only
• Ectopic parathyroid adenoma or hyperplasia due to migratory embryology
• Pseudohypoparathyroidism
• Calcitonin-secreting tumor

Correct Answer: Ectopic parathyroid adenoma or hyperplasia due to migratory embryology

Q46. Which test helps differentiate osteoporosis from bone disease due to long-standing hyperparathyroidism?

• Dual-energy X-ray absorptiometry (DEXA) plus biochemical markers of bone turnover
• Serum sodium measurement only
• Chest X-ray
• Skin biopsy

Correct Answer: Dual-energy X-ray absorptiometry (DEXA) plus biochemical markers of bone turnover

Q47. Which statement is true regarding parathyroid carcinoma?

• It is the most common cause of primary hyperparathyroidism
• It is rare and often presents with very high calcium and markedly elevated PTH
• It never recurs after surgery
• It is usually associated with thyroid hormone excess

Correct Answer: It is rare and often presents with very high calcium and markedly elevated PTH

Q48. Which molecule produced by osteoblasts acts as a decoy receptor to inhibit osteoclastogenesis and is downregulated by PTH?

• RANKL
• Osteoprotegerin (OPG)
• Calcitonin
• Alkaline phosphatase

Correct Answer: Osteoprotegerin (OPG)

Q49. Which of the following is a direct pharmacologic inhibitor of osteoclast activity used in hypercalcemia management?

• Teriparatide
• Bisphosphonates (e.g., zoledronic acid)
• Cinacalcet (acts on CaSR)
• Calcitriol supplementation

Correct Answer: Bisphosphonates (e.g., zoledronic acid)

Q50. Measurement of intact PTH (1–84) is clinically preferred because:

• It measures only PTH fragments with no clinical relevance
• It reflects biologically active full-length hormone and correlates better with clinical state
• It is cheaper but less specific than other assays
• It is unaffected by renal function

Correct Answer: It reflects biologically active full-length hormone and correlates better with clinical state

G S Sachin

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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