Fat Soluble Vitamins Lecture Notes

In this lecture, we cover the four fat-soluble vitamins essential for USMLE and COMLEX exams: Vitamins D, A, K, and E. The mnemonic to remember these is DRAKE. Each vitamin has distinct roles and high-yield points necessary for medical exams.

Overview of Fat Soluble Vitamins

• Four Fat-Soluble Vitamins: D, A, K, E
• Mnemonic: DRAKE (D, R - not a vitamin, A, K, E)

Vitamin D

Functions

• Main Role: Increase calcium levels
• Sites of Action:
  • Distal Renal Tubular: Increases calcium absorption
  • Duodenum: Increases calcium resorption
  • Bone: Activates osteoclasts to destroy bone and release calcium

Types of Vitamin D

• 25 Hydroxy D3:
  • Storage form in the liver
  • Mnemonic: "Oh, the liver is where it lies"
• 1,25 OH2 D3:
  • Active form in the kidney
  • Mnemonic: "but the kidney's 125"

Clinical Facts

• Deficiency:
  • Children: Rickets (bowing knees)
  • Adults: Osteomalacia

Vitamin A

Functions

• Antioxidant:
  • Treats measles and retinitis pigmentosa
• Vision Support:
  • Prevents night blindness
• Cell Activation:
  • Differentiates epithelial cells

Side Effects of Excess

• Alopecia
• Birth Defects: Abnormal pregnancy

Vitamin K

Functions

• Clotting Factor Formation:
  • Factors 2, 7, 9, 10, Protein C, Protein S
• Interaction with Warfarin:
  • Warfarin inhibits vitamin K

High-Yield Facts

• Found in leafy vegetables like kale
• Not present in breast milk (newborns need supplementation)
• Cofactor for gamma carboxylation

Vitamin E

Functions

• Antioxidant
  • Prevents peroxidation of fatty acids
  • Protective against arteriosclerosis

Key Takeaways

• Master these vitamins using mnemonics
• Understand their roles, deficiencies, and high-yield facts