Retinoids naturally occurring, inhibition

Isotretinoin is a retinoid, the class of natural and synthetic compounds that exhibit vitamin A activity. It is a naturally occurring metabolite of vitamin A that inhibits sebum production. The US Food and Drug Administration classifies it as Pregnancy Risk Category X. 

Fisher GJ, Datta SC, Talwar HT, Wanjg ZQ, Varani J, Kang S, Voorhees JJ (1996) Molecular basis of sun-induced premature skin ageing and retinoid antagonism. Nature (London) 379 335-339 Fisher GJ, Talwar H, Lin J, Lin P, McPhillips F, Wang ZQ, Li XY, Wan Y, Kang S, Voorhees JJ (1998) Retinoic acid inhibits induction of c-JUN protein by ultraviolet radiation that occurs subsequent to activation of mito-... 

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