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Steroid skeleton. Carbons 18 and above can be absent.

A steroid is a lipid characterized by a carbon skeleton with four fused rings. All steroids are derived from the acetyl CoA biosynthetic pathway. Different steroids vary in the functional groups attached to these rings. Hundreds of distinct steroids have been identified in plants, animals, and fungi.

Physiology and medicine

Their most important role in most living systems is as hormones. Steroid hormones produce their physiological effects by binding to steroid hormone receptor proteins. The binding of steroid hormones to their receptors causes changes in gene transcription and cell function.

In human physiology and medicine, the most important steroids are cholesterol, the steroid hormones, and their precursors and metabolites. In the bloodstream steroids are bound to carrier proteins.

Cholesterol is an important steroid alcohol, being a common component of animal cell membranes. However, a high level of it can cause various conditions and diseases, such as atherosclerosis. Most other steroids are synthesized from cholesterol. Also, various hormones, including vertebrate sex hormones, are steroids created from cholesterol.



Some of the common categories of steroids include:

In Anatomical Therapeutic Chemical Classification System system, anabolic steroids are classified under A14, sex hormones under G03 and L02, and corticosteroids under A07EA, C05AA, D07, D10AA, H02, R01AD, R03BA, S01BA, S02B, and S03B.


It is also possible to classify steroids based upon their chemical composition. One example of how MeSH performs this classification is available at Wikipedia:MeSH_D04#MeSH_D04.808_---_steroids.


The term steroid is often used more restrictively in specific contexts:


Sex steroids include estrogen (U.S spelling) or oestrogen (UK spelling), progesterone and androgen. Oestrogen and progesterone are made primarily in the ovary and in the placenta during pregnancy and testosterone in the testis.

External links


ca:Esteroide de:Steroide es:Esteroide eo:Steroido fr:Stéroïdehe:סטרואידים nl:Steroïdeno:Steroidpt:Esteróide ro:Steroid sk:Steroid sr:Стероиди th:สเตอรอยด์

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