Thiamine is HY for the USMLE Step 1

THIAMINE aka Vitamin B1

Active form: Thiamine Pyrophosphate (TPP)

Main reactions in which thiamine is a cofactor:
These dehydrogenase reactions generate NADH in the mitochondria which enter the electron transport chain to generate ATP, therefore the patient has a problem making ATP.

Cofactors required by the above 2 enzymes are
Thiamine
Lipoic acid
CO2
Folate
NAD+
Which can be remembered by the phrase, "Tender Love and Care for Nancy"

(Thiamine is also a cofactor for transketolase which catalyzes 2 Carbon transfers in the HMP shunt (pentose phosphate pathway) - required to make Ribose 5 phosphate for nucleotide synthesis)

Classic patient is a Malnourished Alcoholic

Signs and symptoms of deficiency:

Wernicke's Encephalopathy

• Peripheral neuropathy
  
• due to Wallerian degeneration; not drawn (source: Boards and Wards, 3rd Edition)
• occurs since ATP is needed for myelin production and ATP isn't being made to the same quantity
  
• Neuropathy may manifest as foot drop or wrist drop much like lead poisoning does in adults
  
• Wernicke's encephalopathy is reversible (We-versible Wernicke's)

________

Say the above patient was given glucose without correcting his thiamine deficiency, it would precipitate...

Korsakoff's Amneisa

These are the Mammillary Bodies:

These are the mammillary bodies on drugs:

Any questions?
(source: The Medical Journal of Australia )

• anterograde and retrograde amnesia
  
• Bilateral hemorrhagic necrosis of mammillary bodies
  
• mammillary bodies are in the hypothalamus and are part of the limbic system
  
• irreversible
  

Treatment: IV Thiamine and THEN glucose