Discuss the Disorders of Fat-Soluble Vitamins (A, D, E, K)
Unlike water-soluble vitamins, fat-soluble vitamins are stored in the body's fatty tissues and the liver. This means deficiencies often take longer to develop, but toxicities (Hypervitaminosis) are much more common because the body cannot easily flush out the excess.
| Vitamin | Deficiency Disorders | Toxicity (Hypervitaminosis) |
|---|---|---|
| Vitamin A (Retinol) |
Night blindness, Xerophthalmia (dry eyes), Bitot's spots, impaired immunity. | Teratogenic effects (birth defects), skin peeling, enlarged liver, increased intracranial pressure. |
| Vitamin D (Calciferol) |
Rickets (children), Osteomalacia (adults), muscle weakness, bone pain. | Hypercalcemia (high blood calcium), kidney stones, calcification of soft tissues (heart/lungs). |
| Vitamin E (Tocopherol) |
Hemolytic anemia (in infants), nerve damage (ataxia), muscle weakness. | Increased risk of bleeding/hemorrhage (due to interference with Vitamin K). |
| Vitamin K (Phylloquinone) |
Hemorrhagic disease of the newborn, prolonged bleeding/bruising, increased PT time. | Rare, but synthetic forms (Menadione) can cause jaundice or hemolytic anemia in infants. |
Important Clinical Note: Fat-soluble vitamin deficiencies are frequently caused by fat malabsorption syndromes such as Celiac disease, Cystic Fibrosis, or Chronic Pancreatitis, rather than just poor diet alone.
Key Metabolic Roles
- Vitamin A: Essential for the synthesis of rhodopsin (vision) and epithelial cell differentiation.
- Vitamin D: Acts as a hormone to regulate calcium and phosphorus absorption in the gut.
- Vitamin E: A potent antioxidant that protects cell membranes from oxidative stress.
- Vitamin K: A necessary cofactor for the γ-carboxylation of clotting factors II, VII, IX, and X.