Podcast
Questions and Answers
What is the active form of vitamin D3 called?
What is the active form of vitamin D3 called?
Where does the hydroxylation of 25-OH-D3 to its active form occur?
Where does the hydroxylation of 25-OH-D3 to its active form occur?
Which hormone is secreted in response to increased calcium concentration in the blood?
Which hormone is secreted in response to increased calcium concentration in the blood?
What effect does 1,25-dihydroxycholecalciferol have on calcium absorption?
What effect does 1,25-dihydroxycholecalciferol have on calcium absorption?
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What is the primary action of calcitonin in the regulation of calcium levels?
What is the primary action of calcitonin in the regulation of calcium levels?
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Study Notes
Vitamin D3 Metabolism
- Vitamin D3 (cholecalciferol) is obtained from diet or sun exposure.
- The liver converts vitamin D3 to 25-hydroxycholecalciferol (25-OH-D3), an inactive form.
- The kidney hydroxylates 25-OH-D3 to 1,25-dihydroxycholecalciferol (1,25-[OH]2-D3), the active form.
Vitamin D Actions
- The active form of vitamin D increases calcium (Ca2+) absorption in the intestines.
- It enhances parathyroid hormone (PTH) effects on bone resorption.
Calcitonin
- Calcitonin is produced by cells in the thyroid gland.
- Released when blood calcium levels elevate.
- Reduces calcium levels by inhibiting PTH and vitamin D actions.
- Not crucial for normal calcium regulation, but vital during hypercalcemia (high calcium blood).
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Description
Explore the metabolic pathway of Vitamin D3 and its crucial role in calcium regulation. This quiz highlights the transformations in the liver and kidneys and the functions of calcitonin in calcium homeostasis. Test your knowledge on how Vitamin D3 interacts with parathyroid hormone and affects bone health.
