Questions and Answers
What are the symptoms of Vitamin D toxicity in adults?
Fragile bones
What is the consequence of excessive Vitamin D supplementation in some infants?
Hypercalcemia and hyperphosphatemia
Why does excessive exposure to sunlight not lead to Vitamin D toxicity?
Limited capacity to take up cholecalciferol from the skin
What is the negative effect of Vitamin D toxicity on soft tissues?
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Which form of Vitamin E is considered the most active?
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What symptom is associated with hypercalcemia due to Vitamin D toxicity?
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Which enzyme is responsible for the hydroxylation of cholecalciferol at C-25 in the liver?
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What is the active form of vitamin D that is formed after hydroxylation at both C-25 and C-1?
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What controls the enzyme 1-hydroxylase in the kidney?
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In cases of normal or hypercalcemia, which form of Vitamin D is predominantly formed?
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What stimulates the synthesis of Ca-binding protein by Vitamin D?
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Which condition may lead to vitamin D deficiency according to the text?
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What are the symptoms of Vitamin A toxicity as mentioned in the text?
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Which of the following is not a symptom of Vitamin A toxicity according to the text?
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What can happen if Vitamin A intake exceeds the capacity of RBP (retinol binding protein)?
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What is a symptom of Vitamin A deficiency according to the text?
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Study Notes
- Corticosteroids inhibit Vitamin D (VD) activation: normal range is 10-50 ng% for 25-OHVD and 15-45 pg/ml for 1,25-DHVD
- In children, deficiency results in rickets, characterized by protruding abdomen and bone deformities
- In adults, VD deficiency results in osteomalacia, characterized by fragile bones, especially in females
- Toxicity from excessive supplementation can lead to high blood pressure, kidney and myocardial calcinosis, hypercalcemia, and kidney stones
- VD is synthesized from cholesterol in the skin through ultraviolet light
- Vitamin E (α-tocopherol) is essential for antioxidant activity and fat metabolism, synthesized in the body and found in vegetable oils, lettuce, and legumes
- After absorption, VD is transported to the liver, hydroxylated to its active form (1,25-dihydroxycholecalciferol or calcitriol) in the kidney
- Parathyroid hormone, calcium, and phosphate levels regulate the activation of calcitriol
- Vitamin A (retinol) plays a role in growth, development, and immune function, deficiency results in night blindness and increased susceptibility to infectious diseases
- Retinol and retinoic acid have antioxidant and anti-cancer properties
- Carotenes are antioxidants, effective at low oxygen concentrations
- Vitamin A deficiency causes night blindness and xerophthalmia, leading to corneal and skin dryness and blindness
- Vitamin D is a steroid hormone, not sensitive to oxygen, and resistant to alkalies and high temperatures
- Sources of Vitamin D include fish, milk, eggs, and cod liver oil.
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