Question
Which of the following statements regarding calcium handling and parathyroid hormone (PTH) is correct?
| A. |
Calcium reabsorption in the kidney occurs only in the proximal convoluted tubule (PCT)
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| B. |
Calcium reabsorption in the kidney is hormonally regulated in the distal convoluted tubule (DCT)
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| C. |
Parathyroid hormone (PTH) directly increases calcium absorption from the intestine
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| D. |
PTH enhances the action of calcitonin
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Show Answer
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Correct Answer » B
Explanation
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- The distal convoluted tubule (DCT) is the key regulatory site for calcium reabsorption.
- PTH acts here to increase calcium reabsorption via active transport mechanisms.
- This is the clinically and exam-relevant site.
Why Other Options are Incorrect
A. Calcium reabsorption occurs only in PCT
- Incorrect because calcium is reabsorbed in multiple segments:
- PCT, thick ascending limb, and DCT
- Also, PCT is not hormonally regulated
C. PTH directly increases intestinal calcium absorption
- PTH acts indirectly via vitamin D (calcitriol)
D. PTH enhances calcitonin
- PTH and calcitonin have opposite actions
