Steroid

Steroid skeleton of lanosterol. The total number of carbons (30) reflects its triterpenoid origin. In some steroids some carbons may be removed (such as carbon 18) or added (such as carbons 24¹ and 24²) in downstream biosynthetic reactions.

This article is about the chemical family of steroids in general. For an article about the performance enhancing substance, please see Anabolic steroid.

A steroid is a terpenoid lipid characterized by a carbon skeleton with four fused rings. Different steroids vary in the functional groups attached to these rings. Hundreds of distinct steroids have been identified in plants, animals, and fungi. All steroids are derived either from the sterol lanosterol (animals and fungi) or the sterol cycloartenol (plants). Both sterols are derived from the cyclization of the triterpene squalene.

Classification

Taxonomical/Functional

Some of the common categories of steroids:

• Animal steroids
  • Insect steroids
    • Ecdysteroids such as ecdysterone
  • Vertebrate steroids
    • Sex steroids are a subset of sex hormones that produce sex differences or support reproduction. They include androgens, estrogens, and progestagens.
    • Corticosteroids include glucocorticoids and mineralocorticoids. Glucocorticoids regulate many aspects of metabolism and immune function, whereas mineralocorticoids help maintain blood volume and control renal excretion of electrolytes.
    • Anabolic steroids are a class of steroids that interact with androgen receptors to increase muscle and bone synthesis. There are natural and synthetic anabolic steroids. These are the "steroids" used by athletes to increase performance.
• Plant steroids
  • Phytosterols
  • Brassinosteroids
• Fungus steroids
  • Ergosterols

Structural

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.

Origin

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 testes.

External links

• Michael W. King's Medical Biochemistry. Steroids and retinoids are both terpenes which are hydrophobic, pass through cell membranes and bind to intracellular receptors. However, retinoic acid is not a steroid because is does not have the defining ring structure. See: Steroids and Related Hydrophobic Molecules.
• "Biochemistry" by Jeremy M. Berg, John L. Tymoczko and Lubert Stryer (2002) W. H. Freeman and Co. steroid topics in this