Vitamins

Biotin

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Biotin, Vitamin B7, Vitamin H, Coenzyme R

  • Physiology
  1. Water-soluble B-Vitamin (B7)
  2. Biotin is found in many foods (nuts, whole grains, fruits, vegetables)
  3. Biotin carries activated CO2 as a Cofactor of carboxylases, involved in multiple enzymatic reactions (e.g. Glucose and Fatty Acid production)
    1. Oxaloacetate synthesis from pyruvate
    2. Malonyl-CoA synthesis from acteyl-CoA
    3. Methylmalonyl CoA synthesis from Propionyl-CoA
  4. Only small amounts of Biotin are needed
    1. Recommended daily intake: 30 mcg/day (men and women, including pregnancy)
  • Pathophysiology
  • Biotin Deficiency
  1. Biotin deficiency is rare
  2. Biotin deficiency may manifest with dermatologic findings
    1. Hair thinning
    2. Brittle Nails
    3. Skin rashes
  3. Risk Factors
    1. Pregnancy (but Prenatal Vitamins have adequate Biotin)
    2. Alcohol Use Disorder
    3. Malnutrition
    4. Consumption of raw egg whites
      1. Raw egg whites contain avidin Protein which prevents Biotin absorption
      2. Cooking egg whites denatures and deactivates the avidin Protein
    5. Anticonvulsants
      1. Carbamazepine
      2. Phenytoin
      3. Phenobarbital
  • Precautions
  1. No high quality evidence for Biotin supplementation
  2. Many OTC products contain high dose Biotin (>300 up to 5000 mcg/day)
    1. High dose Biotin is found in supplements marketed for hair, skin or Nail Growth
    2. Low dose Biotin (e.g. 30 mcg in Multivitamins)
    3. High dose Biotin Interferes with lab assays (see below)
    4. Hold Biotin 3 days (>72 hours) before lab testing
  • Labs
  • High Dose Biotin (>300 mcg/day) falsely LOWERS other lab levels
  1. Thyroid Stimulating Hormone (TSH)
  2. Beta-HCG
  3. Procalcitonin
  4. Serum Troponin
  • Labs
  • High Dose Biotin (>300 mcg/day) falsely RAISES other lab levels
  1. Serum Free T3
  2. Serum Free T4
  3. Serum Folate
  4. Estradiol
  5. Testosterone
  • References
  1. (2026) Presc Ins 33(3): 8
  2. (2018) Presc Lett 25(2)
  3. LoVecchio Crit Dec Emerg Med (2018) 32(5): 32
  4. Goldberg (2001) Clinical Biochemistry, Medmaster, Miami, p. 43