retinoides

Retinoides, or retinoids, are a broad class of chemical compounds related to vitamin A. They include natural metabolites such as retinol (vitamin A alcohol), retinal (vitamin A aldehyde), and retinoic acids, as well as synthetic analogs used in medicine.

Biologically, retinoids participate in vision and in the regulation of gene expression. In vision, 11-cis-retinal forms part of the photopigment rhodopsin in the retina. At the cellular level, retinoic acids act as ligands for nuclear receptors, namely retinoic acid receptors (RARs) and retinoid X receptors (RXRs), modulating transcription. Through these pathways, retinoids influence cell differentiation, proliferation, and apoptosis, and they are essential for embryonic development and immune function.

Dietary intake provides retinoids via animal-derived retinyl esters and provitamin A carotenoids in plants, which the body can convert to active forms. After absorption, retinoids are stored mainly in the liver and distributed to tissues as needed.

In medicine, retinoids are used topically and systemically. Dermatological retinoids such as tretinoin (all-trans retinoic acid), adapalene, and tazarotene help treat acne, photoaging, and certain keratinization disorders by promoting healthy differentiation of skin cells. Systemic all-trans retinoic acid is a key therapy for acute promyelocytic leukemia. Some synthetic retinoids are employed for psoriasis and other skin conditions. Potential adverse effects include skin irritation, teratogenicity, and photosensitivity, with longer-term systemic use requiring medical monitoring of liver function and lipid levels.

See also: retinoic acid receptors, retinoid X receptors.