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Questions and Answers
What is the active form of vitamin D that increases calcium absorption in the intestine?
What is the active form of vitamin D that increases calcium absorption in the intestine?
- 25-hydroxycholecalciferol
- Cholecalciferol
- 1,25-dihydroxycholecalciferol (correct)
- Calcitonin
What hormone is primarily responsible for increasing the concentration of calcium in the blood?
What hormone is primarily responsible for increasing the concentration of calcium in the blood?
- Calcitonin
- Insulin
- Thyroid stimulating hormone (TSH)
- Parathyroid hormone (PTH) (correct)
Which organ converts vitamin D3 into 25-hydroxycholecalciferol?
Which organ converts vitamin D3 into 25-hydroxycholecalciferol?
- Liver (correct)
- Thyroid gland
- Skin
- Kidney
What triggers the secretion of calcitonin?
What triggers the secretion of calcitonin?
How does calcitonin affect the actions of parathyroid hormone (PTH)?
How does calcitonin affect the actions of parathyroid hormone (PTH)?
Flashcards
25-hydroxycholecalciferol (25-OH-D3)
25-hydroxycholecalciferol (25-OH-D3)
The inactive form of vitamin D produced in the liver.
1,25-dihydroxycholecalciferol (1,25-[OH]2-D3)
1,25-dihydroxycholecalciferol (1,25-[OH]2-D3)
The active form of vitamin D produced in the kidneys.
Active Vitamin D
Active Vitamin D
A hormone that increases calcium absorption in the intestines and enhances the effect of PTH on bone resorption.
Calcitonin
Calcitonin
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Parathyroid Hormone (PTH)
Parathyroid Hormone (PTH)
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Study Notes
Vitamin D3 Metabolism
- Vitamin D3 (cholecalciferol) is obtained through 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 D3 Function
- The active form of vitamin D increases calcium (Ca2+) absorption in the intestines.
- It enhances the effects of parathyroid hormone (PTH) on bone resorption.
Calcitonin
- Calcitonin is secreted by medullary cells in the thyroid gland.
- Its secretion is triggered by elevated blood calcium (Ca2+) levels.
- Calcitonin lowers blood calcium by inhibiting PTH and vitamin D.
- Calcitonin is not typically secreted during normal calcium regulation.
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