Question:
The hormone that promotes the activation of calciferol into calcitriol is:
The hormone that promotes the activation of calciferol into calcitriol is:
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PTH is the primary hypercalcemic hormone.
It elevates blood calcium by bone resorption, decreasing calcium excretion in kidneys, and promoting calcitriol synthesis to increase calcium absorption in the gut.
It elevates blood calcium by bone resorption, decreasing calcium excretion in kidneys, and promoting calcitriol synthesis to increase calcium absorption in the gut.
Updated On: Jul 22, 2026
- Thymosins
- Aldosterone
- Somatostatin
- Parathyroid hormone
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Verified By Collegedunia
The Correct Option is D
Solution and Explanation
Step 1: Understanding the Question:
The question asks for the hormone that stimulates the biochemical conversion of inactive Vitamin D (calciferol) into its active form (calcitriol) in the body.
Step 2: Key Concept and Approach:
The activation of Vitamin D is a two-step process:
1. It is hydroxylated in the liver to 25-hydroxyvitamin D.
2. It is further hydroxylated in the kidney tubules to form active 1,25-dihydroxyvitamin D (calcitriol).
The second renal step is catalyzed by the enzyme 1-$\alpha$-hydroxylase, which is tightly regulated by hormones involved in calcium balance.
Step 3: Detailed Explanation:
• Parathyroid Hormone (PTH): PTH is released by parathyroid glands in response to hypocalcemia (low blood calcium).
It directly stimulates the enzyme 1-$\alpha$-hydroxylase in the proximal tubules of the kidney.
This enzyme converts calciferol derivative to calcitriol.
Calcitriol then increases calcium absorption in the gut.
• Thymosins: These are involved in T-cell maturation and immune function.
• Aldosterone: It acts on the kidneys to promote sodium reabsorption and potassium excretion, having no role in calcium or Vitamin D metabolism.
• Somatostatin: It is an inhibitory hormone that suppresses growth hormone and pancreatic hormone secretion.
Step 4: Final Answer:
Parathyroid hormone promotes the activation of calciferol into calcitriol.
The question asks for the hormone that stimulates the biochemical conversion of inactive Vitamin D (calciferol) into its active form (calcitriol) in the body.
Step 2: Key Concept and Approach:
The activation of Vitamin D is a two-step process:
1. It is hydroxylated in the liver to 25-hydroxyvitamin D.
2. It is further hydroxylated in the kidney tubules to form active 1,25-dihydroxyvitamin D (calcitriol).
The second renal step is catalyzed by the enzyme 1-$\alpha$-hydroxylase, which is tightly regulated by hormones involved in calcium balance.
Step 3: Detailed Explanation:
• Parathyroid Hormone (PTH): PTH is released by parathyroid glands in response to hypocalcemia (low blood calcium).
It directly stimulates the enzyme 1-$\alpha$-hydroxylase in the proximal tubules of the kidney.
This enzyme converts calciferol derivative to calcitriol.
Calcitriol then increases calcium absorption in the gut.
• Thymosins: These are involved in T-cell maturation and immune function.
• Aldosterone: It acts on the kidneys to promote sodium reabsorption and potassium excretion, having no role in calcium or Vitamin D metabolism.
• Somatostatin: It is an inhibitory hormone that suppresses growth hormone and pancreatic hormone secretion.
Step 4: Final Answer:
Parathyroid hormone promotes the activation of calciferol into calcitriol.
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