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8.2 Parathyroid Hormone — Test 1
Q1. Parathyroid hormone secretion is stimulated by:✓ A fall in ionized calcium
Q2. PTH raises plasma calcium by acting on bone to:✓ Increase resorption (osteoclast activity)
Q3. In the kidney, PTH increases calcium reabsorption and also:✓ Increases phosphate excretion (phosphaturia)
Q4. PTH increases intestinal calcium absorption indirectly by:✓ Stimulating renal 1alpha-hydroxylase to make active vitamin D
Q5. The second messenger for PTH at its target tissues is:✓ cAMP
Q6. A rise in urinary cAMP after PTH injection indicates:✓ Intact Gs-adenylate cyclase coupling at the PTH receptor
Q7. Match each PTH action with its site and choose the correct option.✓ A-iii, B-i, C-ii
Q8. PTH is secreted as a polypeptide whose secretion is controlled directly by:✓ The calcium-sensing receptor on parathyroid cells
Q9. The net effect of PTH on plasma calcium and phosphate is:✓ Raise calcium, lower phosphate
Q10. Chronically elevated PTH (hyperparathyroidism) causes bone changes because it:✓ Increases osteoclastic resorption over time
Q11. PTH-related peptide (PTH-rp) acts on PTH receptors and is a common cause of:✓ Humoral hypercalcemia of malignancy
Q12. Intermittent (pulsatile) low-dose PTH (as in teriparatide therapy) can:✓ Stimulate bone formation (anabolic effect)
Q13. PTH increases active vitamin D by stimulating which renal enzyme?✓ 1alpha-hydroxylase
Q14. The PTH effect that prevents calcium-phosphate precipitation despite rising calcium is:✓ Renal phosphate excretion
Q15. In response to hypocalcemia, the integrated PTH response includes all EXCEPT:✓ Increased renal phosphate reabsorption
Q16. The cells that secrete PTH are located in the:✓ Parathyroid glands
Q17. PTH and PTH-rp share the same receptor, which is why PTH-rp can:✓ Reproduce PTH's hypercalcemic actions
Q18. Why is PTH the principal minute-to-minute calcium regulator?✓ It acts rapidly on bone and kidney in response to small Ca2+ changes
Q19. A patient with high calcium and SUPPRESSED PTH most likely has:✓ A non-parathyroid cause (e.g. malignancy/PTH-rp)
Q20. The overall purpose of PTH is to:✓ Defend plasma calcium against hypocalcemia