Retinoic acid—a review

Abstract
Retinoic acid (RA) is now considered a normal metabolite of vitamin A. It has been established that RA maintains health and supports growth in animals but differs from other forms of vitamin A in that RA does not function in visual or reproductive processes. RA and RA analogs also differ from other forms of vitamin A in: absorption, transport, metabolism, storage, turnover, biochemical functions, excretion, pharmacology, and toxicology.