Retinoid

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The Retinoids are a class of chemical compounds that are related chemically to vitamin A. Retinoids are used in medicine, primarily due to the way they regulate epithelial cell growth.

Retinoids have many important and diverse functions throughout the body including roles in vision, regulation of cell proliferation and differentiation, bone growth, immune defense and tumor suppression.

Research is also being done into their ability to treat epithelial cancers. Currently 9-cis retinoic acid may be used topically to help treat skin lesions from Kaposi's sarcoma.

Contents

1 Types
2 Structure
3 Uses
4 Toxicity
5 References
6 See also

Types

There are three generations of Retinoids:

First generation retinoids: which include retinol, tretinoin, isotretinoin and alitretinoin.

Second generation retinoids: which include etretinate and its metabolite acitretin.

Third generation retinoids: which include tazarotene and bexarotene.

Structure

The basic structure of the retinoid molecule consist of a cyclic end group, a polyene side chain and a polar end group. Alternation of side chains and end groups creates the various classes of retinoids. First and Second generation retinoids are able to bind with several retinoid receptors due to the flexibility imparted by their alternating single and double bonds. Third generation retinoids are less flexible than First and Second generation retinoids and therefore, interact with fewer retinoids receptors.

Uses

Retinoids are used in the treatment of many diverse diseases and are effective in the treatment of inflammatory skin disorders, skin malignancies, hyperproliferative disorders, photoaging etc. Most important of them are acne and psoriasis.

Toxicity

Toxic effects occur with prolonged high intake (in children 25,000-500,000 IU daily. A diagnostic sign of chronic poisoning is the presence of painful tender swellings on the long bones. Anorexia, skin lesions, hair loss, hepatosplenomegaly, papilloedema, bleeding and general malaise also occur.

Chronic overdose also causes an increased liability of biological membranes and of the outer layer of the skin to peel.

As vitamin A (retinoids) is stored in the liver Eskimos never eat polar-bear liver, knowing it to be toxic, and husky dogs, with instinctive wisdom, also avoid it

References

The Pharmacological Basis of Therapeutics -Goodman & Gilman 10th EDT.