Difference between revisions of "Steroid" - New World Encyclopedia
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| − | [[Image:Steroid-nomenclature.png|thumb|right|250px|Steroids, such as cholesterol and the steroid | + | [[Image:Steroid-nomenclature.png|thumb|right|250px|'''Steroids''', such as [[cholesterol]] and the steroid [[hormone]]s, are characterized by a [[carbon skeleton]] with four fused rings. They are distinguished by the functional groups attached to the rings.]] |
A '''steroid''' is any of a group of natural or synthetic, fat-soluble, organic compounds belonging to the class of [[lipid]]s and characterized by a molecular core of four fused rings totaling 17 [[carbon]] atoms: three six-carbon rings and one five-carbon ring fused together. The type of steroid is determined by the three-dimensional configuration and the type of additional side chains and rings. | A '''steroid''' is any of a group of natural or synthetic, fat-soluble, organic compounds belonging to the class of [[lipid]]s and characterized by a molecular core of four fused rings totaling 17 [[carbon]] atoms: three six-carbon rings and one five-carbon ring fused together. The type of steroid is determined by the three-dimensional configuration and the type of additional side chains and rings. | ||
| − | Steroids include such varieties as sterols, bile acids, adrenal and sex hormones, among others, and are ubiquitous in nature, being found in [[animal]]s, [[plant]]s, [[fungi]] | + | Steroids include such varieties as sterols, bile acids, adrenal and sex hormones, among others, and are ubiquitous in nature, being found in [[animal]]s, [[plant]]s, [[fungi]] and [[protozoa]]. [[Cholesterol]] is the most abundant steroid in [[mammal]]ian [[cell (biology)|cells]]. These various steroids perform many key biological functions, including involvement in [[cell membrane]]s and serving as [[hormone]]s. Steroids help to stimulate [[bone]] and [[muscle]] growth, puberty, tissue synthesis, and regulate metabolism and immune function. They are used medically, such as part of treatments of [[cancer]] and [[AIDS]]. |
| − | However, some steroids also have been used inappropriately. A well-known example is the use of anabolic steroids in competitive | + | However, some steroids also have been used inappropriately. A well-known example is the use of anabolic steroids in competitive [[sport]]s to gain an edge over other competitors, causing the danger of side effects to the user and harm to the integrity of the sport. |
==Chemistry== | ==Chemistry== | ||
[[Image:Lanosterol structure.svg|thumb|right|250px|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 24<sup>1</sup> and 24<sup>2</sup>) in downstream biosynthetic reactions.]] | [[Image:Lanosterol structure.svg|thumb|right|250px|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 24<sup>1</sup> and 24<sup>2</sup>) in downstream biosynthetic reactions.]] | ||
| − | Steroids belong to the class of biochemicals called [[lipid]]s. Along with [[protein]]s, [[nucleic acid]]s, and [[carbohydrate]]s, lipids are one of the major classes of biologically important molecules (or biomolecules). They are water-insoluble, organic compounds that are highly soluble in nonpolar organic solvents. In addition to steroids, other lipids include [[fatty acid]]s, glycerides (such as [[fat|triglyceride]]s or fat), [[phospholipid]]s, and more complex lipid derivatives such as glycolipids (sugar-linked lipids). | + | Steroids belong to the class of biochemicals called [[lipid]]s. Along with [[protein]]s, [[nucleic acid]]s, and [[carbohydrate]]s, lipids are one of the major classes of biologically important molecules (or biomolecules). They are water-insoluble, organic compounds that are highly soluble in nonpolar organic solvents. In addition to steroids, other lipids include [[fatty acid]]s, glycerides (such as [[fat|triglyceride]]s or fat), [[phospholipid]]s, and more complex lipid derivatives such as glycolipids ([[sugar]]-linked lipids). |
| − | A steroid is a lipid characterized by a [[carbon]] skeleton with four fused rings known as a cyclopentanoperhydrophenanthrene ring system. There are three fused six-carbon rings (cyclohexane) and a five-carbon ring (cyclopentane), fused such that there are a total of 17 carbon | + | A steroid is a lipid characterized by a [[carbon]] skeleton with four fused rings known as a cyclopentanoperhydrophenanthrene ring system. There are three fused six-carbon rings (cyclohexane) and a five-carbon ring (cyclopentane), fused such that there are a total of 17 carbon [[atom]]s in the molecular nucleus. Different steroids vary in the functional groups attached to these rings. 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 (IUBMB 2000). |
==Categories of steroids== | ==Categories of steroids== | ||
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**[[Vertebrate]] steroids | **[[Vertebrate]] steroids | ||
***[[Sex steroid]]s are a subset of sex hormones that produce sex differences or support [[reproduction]]. They include [[androgen]]s, [[estrogen]]s, and [[progestagen]]s. | ***[[Sex steroid]]s are a subset of sex hormones that produce sex differences or support [[reproduction]]. They include [[androgen]]s, [[estrogen]]s, and [[progestagen]]s. | ||
| − | ***[[Corticosteroid]]s include [[glucocorticoid]]s and [[mineralocorticoid]]s. Glucocorticoids regulate many aspects of [[metabolism]] and [[immune system|immune function]], whereas mineralocorticoids help maintain blood volume and control [[kidney|renal]] excretion of electrolytes. | + | ***[[Corticosteroid]]s include [[glucocorticoid]]s and [[mineralocorticoid]]s. Glucocorticoids regulate many aspects of [[metabolism]] and [[immune system|immune function]], whereas mineralocorticoids help maintain blood volume and control [[kidney|renal]] excretion of electrolytes. |
***[[Anabolic steroid]]s 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. | ***[[Anabolic steroid]]s 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. | ||
***[[Cholesterol]] modulates the fluidity of [[cell membrane]]s and is the principle constituent of the plaques implicated in [[atherosclerosis]]. | ***[[Cholesterol]] modulates the fluidity of [[cell membrane]]s and is the principle constituent of the plaques implicated in [[atherosclerosis]]. | ||
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==Cholesterol== | ==Cholesterol== | ||
| − | [[Image:Cholesterol structure.png|thumb|right|249px|The chemical structure of cholesterol, showing the molecular core of 17 carbon atoms in four fused rings.]] | + | [[Image:Cholesterol structure.png|thumb|right|249px|The chemical structure of [[cholesterol]], showing the molecular core of 17 carbon atoms in four fused rings.]] |
| − | '''Cholesterol''' is a [[sterol]] lipid (a combination steroid and [[alcohol]]) with the chemical formula C<sub>27</sub>H<sub>45</sub>OH. It is found in the cell membranes of all [[human body]] tissues, and transported in the [[blood]] plasma of all [[animal]]s. | + | '''[[Cholesterol]]''' is a [[sterol]] lipid (a combination steroid and [[alcohol]]) with the chemical formula C<sub>27</sub>H<sub>45</sub>OH. It is found in the cell membranes of all [[human body]] tissues, and transported in the [[blood]] plasma of all [[animal]]s. Lesser amounts of cholesterol are also found in [[plant]] membranes. |
| − | Cholesterol is an important component of cell | + | Cholesterol is an important component of [[cell membrane]]s, which enhances their fluidity. Cholesterol also aids in the manufacture of [[bile]] (which helps digest [[fat]]s), and is also important for the [[metabolism]] of fat-soluble [[vitamin]]s. |
==Steroid hormones== | ==Steroid hormones== | ||
| Line 45: | Line 45: | ||
[[Vitamin D]] derivatives are a sixth closely related hormone system with homologous receptors. Steroid hormones produce their physiological effects by binding to steroid hormone receptor proteins, which causes changes in [[gene]] transcription and cell function. | [[Vitamin D]] derivatives are a sixth closely related hormone system with homologous receptors. Steroid hormones produce their physiological effects by binding to steroid hormone receptor proteins, which causes changes in [[gene]] transcription and cell function. | ||
| − | The natural steroid hormones are generally synthesized from [[cholesterol]] in the [[gonad]]s and [[adrenal gland]]s. Because these steroids are lipid soluble, they can [[diffusion|diffuse]] fairly freely from the blood through the [[cell membrane]] and into the [[cytoplasm]] of target cells. In the cytoplasm, the steroid may or may not undergo an [[enzyme]]-mediated alteration such as reduction, hydroxylation, or aromatization. In the cytoplasm, the steroid binds to the specific receptor, a large metalloprotein. Upon steroid binding, many kinds of steroid receptor [[dimer|dimerize]]: two receptor subunits join together to form one functional [[DNA]]-binding unit that can enter the [[cell nucleus]]. Once in the nucleus, the steroid-receptor ligand complex binds to specific | + | The natural steroid hormones are generally synthesized from [[cholesterol]] in the [[gonad]]s and [[adrenal gland]]s. Because these steroids are lipid soluble, they can [[diffusion|diffuse]] fairly freely from the blood through the [[cell membrane]] and into the [[cytoplasm]] of target cells. In the cytoplasm, the steroid may or may not undergo an [[enzyme]]-mediated alteration such as reduction, hydroxylation, or aromatization. In the cytoplasm, the steroid binds to the specific receptor, a large metalloprotein. Upon steroid binding, many kinds of steroid receptor [[dimer|dimerize]]: two receptor subunits join together to form one functional [[DNA]]-binding unit that can enter the [[cell nucleus]]. Once in the nucleus, the steroid-receptor ligand complex binds to specific DNA sequences and induces transcription of its target [[gene]]s. |
Steroid hormones are generally carried in the blood bound to specific carrier [[protein]]s such as sex hormone binding globulin or corticosteroid binding globulin. Further conversions and catabolism occurs in the [[liver]], other "peripheral" tissues, and in the target tissues. | Steroid hormones are generally carried in the blood bound to specific carrier [[protein]]s such as sex hormone binding globulin or corticosteroid binding globulin. Further conversions and catabolism occurs in the [[liver]], other "peripheral" tissues, and in the target tissues. | ||
| Line 54: | Line 54: | ||
[[Image:Testosterone structure.png|thumb|230px|Chemical structure of the natural anabolic hormone [[testosterone]], 17b-hydroxy-4-androsten-3-one.]] | [[Image:Testosterone structure.png|thumb|230px|Chemical structure of the natural anabolic hormone [[testosterone]], 17b-hydroxy-4-androsten-3-one.]] | ||
| − | '''Anabolic androgenic steroids''' or AAS are a class of natural and synthetic steroid [[hormone]]s that promote cell growth and division, resulting in growth of several types of [[tissue]]s, especially [[muscle]] and [[bone]]. Different anabolic androgenic steroids have varying combinations of [[androgen]]ic ''and'' [[metabolism|anabolic]] properties, and are often referred to in medical texts as AAS (anabolic/androgenic steroids). | + | '''Anabolic androgenic steroids''' or AAS are a class of natural and synthetic steroid [[hormone]]s that promote cell growth and division, resulting in growth of several types of [[tissue]]s, especially [[muscle]] and [[bone]]. Different anabolic androgenic steroids have varying combinations of [[androgen]]ic ''and'' [[metabolism|anabolic]] properties, and are often referred to in medical texts as AAS (anabolic/androgenic steroids). Anabolism is the metabolic process that builds larger molecules from smaller ones. |
| − | Anabolic steroids were first discovered in the early 1930s and have since been used for numerous medical purposes, including stimulation of bone growth, [[appetite]], [[puberty]], and muscle growth. The most widespread use of anabolic steroids is their use for chronic wasting conditions, such as [[cancer]] and [[AIDS]]. Anabolic steroids can produce numerous physiological effects including increases in protein synthesis, muscle mass, strength, appetite, and bone growth. Anabolic steroids have also been associated with numerous side effects when administered in excessive doses and these include elevated [[cholesterol]],[[acne]], elevated blood pressure, hepatotoxicity | + | Anabolic steroids were first discovered in the early 1930s and have since been used for numerous medical purposes, including stimulation of bone growth, [[appetite]], [[puberty]], and muscle growth. The most widespread use of anabolic steroids is their use for chronic wasting conditions, such as [[cancer]] and [[AIDS]]. Anabolic steroids can produce numerous physiological effects including increases in protein synthesis, muscle mass, strength, appetite, and bone growth. Anabolic steroids have also been associated with numerous side effects when administered in excessive doses and these include elevated [[cholesterol]], [[acne]], elevated blood pressure, hepatotoxicity and alterations in [[heart|left ventricle]] [[Morphology (biology)|morphology]]. |
Today anabolic steroids are controversial because of their widespread use in competitive sports and their associated side effects. | Today anabolic steroids are controversial because of their widespread use in competitive sports and their associated side effects. | ||
| Line 62: | Line 62: | ||
==References== | ==References== | ||
| − | * Agis-Balboa, R. C., et al. 2006. Characterization of brain neurons that express enzymes mediating neurosteroid biosynthesis. ''Proc Natl Acad Sci U.S.A'' | + | * Agis-Balboa, R. C., et al. 2006. Characterization of brain neurons that express enzymes mediating neurosteroid biosynthesis. ''Proc Natl Acad Sci U.S.A'' 103: 14602-14607. PMID 16984997 |
| − | * Belelli, D., and J. J. Lambert. 2005. Neurosteroids: Endogenous regulators of the GABA<sub>A</sub> receptor. ''Nature Reviews Neuroscience'' | + | * Belelli, D., and J. J. Lambert. 2005. Neurosteroids: Endogenous regulators of the GABA<sub>A</sub> receptor. ''Nature Reviews Neuroscience'' 6: 565-575. PMID 15959466 |
| − | * Dubrovsky, B. O. 2005. Steroids, neuroactive steroids and neurosteroids in psychopathology. ''Prog Neuropsychopharmacol Biol Psychiatry'' | + | * Dubrovsky, B. O. 2005. Steroids, neuroactive steroids and neurosteroids in psychopathology. ''Prog Neuropsychopharmacol Biol Psychiatry'' 29: 169-192. PMID 15694225 |
| − | * International Union of Biochemistry and Molecular Biology (IUBMB). 2000. [http://www.chem.qmul.ac.uk/iubmb/enzyme/reaction/terp/lanost.html Lanosterol and cycloartenol biosynthesis] | + | * International Union of Biochemistry and Molecular Biology (IUBMB). 2000. [http://www.chem.qmul.ac.uk/iubmb/enzyme/reaction/terp/lanost.html Lanosterol and cycloartenol biosynthesis.] ''International Union of Biochemistry and Molecular Biology''. Retrieved January 6, 2008. |
| − | * Mellon, S. H., and L. D. Griffin. 2002. Neurosteroids: biochemistry and clinical significance. ''Trends Endocrinol Metab'' 13: 35-43. PMID 11750861 | + | * Mellon, S. H., and L. D. Griffin. 2002. Neurosteroids: biochemistry and clinical significance. ''Trends Endocrinol Metab'' 13: 35-43. PMID 11750861 |
| − | * Pinna, G., et al. 2005. Fluoxetine and norfluoxetine stereospecifically and selectively increase brain neurosteroid content at doses that are inactive on 5-HT reuptake. ''Psychopharmacology'' 186:362-372. PMID 16432684 | + | * Pinna, G., et al. 2005. Fluoxetine and norfluoxetine stereospecifically and selectively increase brain neurosteroid content at doses that are inactive on 5-HT reuptake. ''Psychopharmacology'' 186: 362-372. PMID 16432684 |
== External links == | == External links == | ||
| − | + | All links retrieved January 6, 2008. | |
| − | |||
| + | * [http://www.indstate.edu/thcme/mwking/steroid-hormones.html Michael W. King's Medical Biochemistry] | ||
| + | * [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=stryer.TOC&depth=2 ''Biochemistry''] by Jeremy M. Berg, John L. Tymoczko and Lubert Stryer. 2002. W. H. Freeman and Co. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=Books&cmd=Search&term=steroid+AND+stryer%5Bbook%5D&doptcmdl=TOC View steroid topics in this book.] | ||
| − | [[Category: | + | [[Category:Anatomy and Physiology]] |
{{credit|Steroid|120869621|Steroid_hormone|122162270|Anabolic_steroid|122867717}} | {{credit|Steroid|120869621|Steroid_hormone|122162270|Anabolic_steroid|122867717}} | ||
Revision as of 01:24, 7 January 2008
A steroid is any of a group of natural or synthetic, fat-soluble, organic compounds belonging to the class of lipids and characterized by a molecular core of four fused rings totaling 17 carbon atoms: three six-carbon rings and one five-carbon ring fused together. The type of steroid is determined by the three-dimensional configuration and the type of additional side chains and rings.
Steroids include such varieties as sterols, bile acids, adrenal and sex hormones, among others, and are ubiquitous in nature, being found in animals, plants, fungi and protozoa. Cholesterol is the most abundant steroid in mammalian cells. These various steroids perform many key biological functions, including involvement in cell membranes and serving as hormones. Steroids help to stimulate bone and muscle growth, puberty, tissue synthesis, and regulate metabolism and immune function. They are used medically, such as part of treatments of cancer and AIDS.
However, some steroids also have been used inappropriately. A well-known example is the use of anabolic steroids in competitive sports to gain an edge over other competitors, causing the danger of side effects to the user and harm to the integrity of the sport.
Chemistry
Steroids belong to the class of biochemicals called lipids. Along with proteins, nucleic acids, and carbohydrates, lipids are one of the major classes of biologically important molecules (or biomolecules). They are water-insoluble, organic compounds that are highly soluble in nonpolar organic solvents. In addition to steroids, other lipids include fatty acids, glycerides (such as triglycerides or fat), phospholipids, and more complex lipid derivatives such as glycolipids (sugar-linked lipids).
A steroid is a lipid characterized by a carbon skeleton with four fused rings known as a cyclopentanoperhydrophenanthrene ring system. There are three fused six-carbon rings (cyclohexane) and a five-carbon ring (cyclopentane), fused such that there are a total of 17 carbon atoms in the molecular nucleus. Different steroids vary in the functional groups attached to these rings. 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 (IUBMB 2000).
Categories of steroids
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.
- Cholesterol modulates the fluidity of cell membranes and is the principle constituent of the plaques implicated in atherosclerosis.
- Insect steroids
- Plant steroids
- Phytosterols
- Brassinosteroids
- Fungus steroids
- Ergosterols
Cholesterol
Cholesterol is a sterol lipid (a combination steroid and alcohol) with the chemical formula C27H45OH. It is found in the cell membranes of all human body tissues, and transported in the blood plasma of all animals. Lesser amounts of cholesterol are also found in plant membranes.
Cholesterol is an important component of cell membranes, which enhances their fluidity. Cholesterol also aids in the manufacture of bile (which helps digest fats), and is also important for the metabolism of fat-soluble vitamins.
Steroid hormones
Cholesterol is an important precursor of the steroid hormones. Steroid hormones are steroids that act as hormones. Mammalian steroid hormones can be grouped into five groups by the receptors to which they bind:
- Androgens (such as testosterone) are responsible for the development of male secondary sex characteristics.
- Glucocorticoids enable animals to respond to stress. They regulate many aspects of metabolism and immune function, and are often prescribed by doctors to reduce inflammatory conditions like asthma and arthritis.
- Mineralocorticoids help maintain blood volume and control renal excretion of electrolytes.
- Estrogens and progestagens are two classes of sex steroids, a subset of the hormones that produce sex differences or support reproduction.
Vitamin D derivatives are a sixth closely related hormone system with homologous receptors. Steroid hormones produce their physiological effects by binding to steroid hormone receptor proteins, which causes changes in gene transcription and cell function.
The natural steroid hormones are generally synthesized from cholesterol in the gonads and adrenal glands. Because these steroids are lipid soluble, they can diffuse fairly freely from the blood through the cell membrane and into the cytoplasm of target cells. In the cytoplasm, the steroid may or may not undergo an enzyme-mediated alteration such as reduction, hydroxylation, or aromatization. In the cytoplasm, the steroid binds to the specific receptor, a large metalloprotein. Upon steroid binding, many kinds of steroid receptor dimerize: two receptor subunits join together to form one functional DNA-binding unit that can enter the cell nucleus. Once in the nucleus, the steroid-receptor ligand complex binds to specific DNA sequences and induces transcription of its target genes.
Steroid hormones are generally carried in the blood bound to specific carrier proteins such as sex hormone binding globulin or corticosteroid binding globulin. Further conversions and catabolism occurs in the liver, other "peripheral" tissues, and in the target tissues.
Estrogen (oestrogen) and progesterone are made primarily in the ovary and in the placenta during pregnancy and testosterone in the testes.
Anabolic steroids
Anabolic androgenic steroids or AAS are a class of natural and synthetic steroid hormones that promote cell growth and division, resulting in growth of several types of tissues, especially muscle and bone. Different anabolic androgenic steroids have varying combinations of androgenic and anabolic properties, and are often referred to in medical texts as AAS (anabolic/androgenic steroids). Anabolism is the metabolic process that builds larger molecules from smaller ones.
Anabolic steroids were first discovered in the early 1930s and have since been used for numerous medical purposes, including stimulation of bone growth, appetite, puberty, and muscle growth. The most widespread use of anabolic steroids is their use for chronic wasting conditions, such as cancer and AIDS. Anabolic steroids can produce numerous physiological effects including increases in protein synthesis, muscle mass, strength, appetite, and bone growth. Anabolic steroids have also been associated with numerous side effects when administered in excessive doses and these include elevated cholesterol, acne, elevated blood pressure, hepatotoxicity and alterations in left ventricle morphology.
Today anabolic steroids are controversial because of their widespread use in competitive sports and their associated side effects.
ReferencesISBN links support NWE through referral fees
- Agis-Balboa, R. C., et al. 2006. Characterization of brain neurons that express enzymes mediating neurosteroid biosynthesis. Proc Natl Acad Sci U.S.A 103: 14602-14607. PMID 16984997
- Belelli, D., and J. J. Lambert. 2005. Neurosteroids: Endogenous regulators of the GABAA receptor. Nature Reviews Neuroscience 6: 565-575. PMID 15959466
- Dubrovsky, B. O. 2005. Steroids, neuroactive steroids and neurosteroids in psychopathology. Prog Neuropsychopharmacol Biol Psychiatry 29: 169-192. PMID 15694225
- International Union of Biochemistry and Molecular Biology (IUBMB). 2000. Lanosterol and cycloartenol biosynthesis. International Union of Biochemistry and Molecular Biology. Retrieved January 6, 2008.
- Mellon, S. H., and L. D. Griffin. 2002. Neurosteroids: biochemistry and clinical significance. Trends Endocrinol Metab 13: 35-43. PMID 11750861
- Pinna, G., et al. 2005. Fluoxetine and norfluoxetine stereospecifically and selectively increase brain neurosteroid content at doses that are inactive on 5-HT reuptake. Psychopharmacology 186: 362-372. PMID 16432684
External links
All links retrieved January 6, 2008.
- Michael W. King's Medical Biochemistry
- Biochemistry by Jeremy M. Berg, John L. Tymoczko and Lubert Stryer. 2002. W. H. Freeman and Co. View steroid topics in this book.
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