Term
| Where is Vitamin A stored? |
|
Definition
| Vitamin A is fat soluble and is accumulates in the liver. Storage last a long time so deficiency takes a long time to produce symptoms. |
|
|
Term
| What are the symptoms of Vitamin A deficiency? |
|
Definition
Earliest:
-Night blindness
General:
-hyperkeratosis of skin
-anemia
-increased susceptibility to infections
Advanced:
-xerophthalmia (destructive dryness of conjunctival epithelium causing corneal ulcerization, irreversible damage, and blindness) |
|
|
Term
| With what conditions is Vit A deficiency most often associated with in the US? |
|
Definition
| liver damage and impaired fat absorption (in developing countries it's diet deficiency) |
|
|
Term
| Where do carotenes come from? |
|
Definition
| Dark green leafy vegetables and yellow fruits and vegetables |
|
|
Term
| What form of Vitamin A do Egg yolks contain? |
|
Definition
| xanthophylls (similar to carotenes) |
|
|
Term
| What forms of Vitamin A are found in the liver? |
|
Definition
| Retinol and retinyl esters |
|
|
Term
| Which form of Vitamin A is used in supplements? |
|
Definition
| Retinyl ester (ester form of retinol; retinol and retinal aren't stable) |
|
|
Term
| How can Vitamin A toxicity occur? |
|
Definition
| Can only result from ingestion of animal liver or vitamin supplements (5-50 mg RE/day over many months) |
|
|
Term
| What are the symptoms of Vitamin A Toxicity? |
|
Definition
| Bone and muscle pain, scaly dermatitis, nausea, diarrhea, and liver and spleen enlargement |
|
|
Term
| What forms of Vitamin A can be used to prevent cancer? |
|
Definition
| Topical or oral retinoic acid; Beta-carotene and other carotenes don't have this effect |
|
|
Term
| How does retinoic acid prevent cancer? |
|
Definition
| Metaplasia-inducing effect which seems to counteract the actions of oncogenes on cell regulation |
|
|
Term
| What are Vitamin D's sources? |
|
Definition
In skin:
7-dehydrocholesterol + UVB --> cholecalciferol (Vit D3)
In yeast:
ergosterol + UVB ---> ergocalciferol (Vit D2)
-Ergocalciferol is used to fortify milk, butter, and other foods
-Cholecalciferol is also found in fatty fish, fish liver oils, liver, and egg yolk |
|
|
Term
| Which form of Vitamin D regulates all calcium regulation? What is it's mechanism? |
|
Definition
| Calcitriol - acts by binding to and activating a nuclear (steroid-like) receptor |
|
|
Term
| Which form of Vitamin D will produced if there is High calcitrol or low PTH? |
|
Definition
24,25 dihydroxycholecalciferol
-has some activity for regulating cells |
|
|
Term
| Which form of Vitamin D will be produced if there is high PTH in the environment? |
|
Definition
Calcitriol
-calcitriol receptors are found in many cell types so it has many functions other than regulating calcium homeostasis |
|
|
Term
| What happens to children who have Vitamin D deficiency? |
|
Definition
| Rickets - inadequate bone matrix mineralization --> soft, pliable bones |
|
|
Term
| What causes Vit D deficiency? |
|
Definition
| No calcium absorption from gut; calcium homeostasis occurs at the expense of bone |
|
|
Term
| What happens to adults who have Vit D deficiency? |
|
Definition
| Osteomalacia - demineralization of bone causing soft bones that are prone to fracture |
|
|
Term
| What is hypocalcemic tetany? |
|
Definition
| Muscle spasms caused by a calcium/Vit D deficiency |
|
|
Term
| What are the symptoms of Vit D toxicity? |
|
Definition
| hypercalcemia, hypercalciuria, kidney stones, bone demineralization (similar to deficiency), metastatic calcification |
|
|
Term
| What serum levels of Calcidiol are healthy? |
|
Definition
<10-11 ng/mL: vit D deficiency
<10-15 ng/mL: inadequate for bone and overall health in healthy individuals
>15: adequate for overall health and bone health
Consistently >200: toxic |
|
|
Term
| How do serum levels of Vitamin D compare in obese people? |
|
Definition
| Since it distributes to fat, serum levels are lower in obese people with the same total body level as lean people |
|
|
Term
| What can be done for cystic fibrosis patients to help with malabsorption? |
|
Definition
-CF patients have decreased fat digestion and absorption --> decreased uptake of fat soluble soluble vitamins
-orally active pancreatic enzyme microspheres have helped
-use high protein/high carb supplements containing shortchain fatty acids that are easily absorbed
-supplementation with 2x normal RDA of fat soluble vitamins |
|
|
Term
|
Definition
1. LOW SERUM CALCIUM
-High PTH
-Low calcitonin
-calcium from bone and diet is used to make calcidiol
2. HIGH SERUM CALCIUM
-Low PTH
-High calcitonin
-serum calcium is absorbed in bone and excreted in urine; no calcium absorption from diet
3. LOW VITAMIN D
-High PTH
-Low Calcitonin
-calcium from bone is converted to serum calcium
4. EXCESS VITAMIN D
-Low PTH
-High Calcitonin
-Calcium from diet, bone, and serum are excreted in the urine or converted to calcidiol or 24,25-(OH)2-D
|
|
|
