Vitamin A

  • Also called retinol
  • Function
    • Antioxidant; constituent of visual pigments (retinal); essential for normal differentiation of epithelial cells into specialized tissue (pancreatic cells, mucus-secreting cells, conjunctiva, keratinocytes); prevents squamous metaplasia. Used to treat measles and acute promyelocytic leukemia (APL).
    • Retinol is vitamin A, so think retin-A (used topically for wrinkles and Acne).
    • Found in liver and leafy vegetables, with beta carotene
    • Use oral isotretinoin (13-cis-isomer of naturally occuring all-trans-retinoic acid) to treat severe cystic acne. Inhibit follicular epidermal keratinization, loosening keratin plugs of comedones & facilitating their expulsion. Reduce size of sebaceous glands & inhibit serum production.
    • Use all-trans retinoic acid to treat acute promyelocytic leukemia.


  • Deficiency
    • Night blindness (nyctalopia); dry, scaly skin (xerosis cutis); corneal degeneration (keratomalacia); Bitot spots (foamy appearance) on conjunctiva; immunosuppression, growth retardation.
    • Caused by insufficient dietary intake, pancreatic insufficiency (chronic pancreatitis, cystic fibrosis), cholestatic liver disease/biliary obstruction, intestinal malabsorption (IBD, bariatric surgery)
  • Excess
    • Acute toxicity—nausea, vomiting, vertigo, and blurred vision.
    • Chronic toxicity—alopecia, dry skin (eg, scaliness), cheilitis, myalgias, arthralgias, and pseudotumor cerebri.
      • Hepatic toxicity and enlargement -less evident in isotretinoin toxicity because it is NOT stored in the liver (unlike natural Vitamin A)
    • Teratogenic (cleft palate, cardiac abnormalities, microcephaly, fetal death), therefore a ⊝ pregnancy test and two forms of contraception are required before isotretinoin (vitamin A derivative) is prescribed.
    • Isotretinoin is teratogenic.

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