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A steroid is a biologically active
organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during ...
with four rings arranged in a specific
molecular configuration The molecular configuration of a molecule is the ''permanent'' geometry that results from the space, spatial arrangement of its chemical bond, bonds. The ability of the same set of atoms to form two or more molecules with different configurations i ...
. Steroids have two principal biological functions: as important components of
cell membrane cell membrane vs. Prokaryotes A prokaryote is a typically unicellular organism that lacks a nuclear membrane-enclosed cell nucleus, nucleus. The word ''prokaryote'' comes from the Greek language, Greek (, 'before') and (, 'nut' or 'kernel').C ...

cell membrane
s which alter
membrane fluidityIn biology, membrane fluidity refers to the viscosity The viscosity of a fluid is a measure of its drag (physics), resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup ...
; and as
signaling molecules In biology, cell signaling (cell signalling in British English), or cell-cell communication, governs the basic activities of cell (biology), cells and coordinates multiple-cell actions. A signal is an entity that codes or conveys information. Biolo ...
. Hundreds of steroids are found in
plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel ...

plant
s,
animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells ...

animal
s and
fungi A fungus (plural The plural (sometimes abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken from the full ...

fungi
. All steroids are manufactured in cells from the
sterols Sterol is an organic compound with formula , whose molecule is derived from that of gonane by replacement of a hydrogen atom in position 3 by a hydroxyl group. It is therefore an alcohol (chemistry), alcohol of gonane. More generally, any compounds ...

sterols
lanosterol Lanosterol is a tetracyclic triterpenoid Triterpenes are a class of chemical compounds composed of three terpene units with the molecular formula C30H48; they may also be thought of as consisting of six isoprene units. Animals, plants and fungi a ...

lanosterol
(
opisthokonts The opisthokonts (Greek language , Greek: (''opísthios'')="rear, posterior" + (''kontós'')="pole" i.e. "flagellum") are a broad group of eukaryotes, including both the animal and fungus kingdom (biology) , kingdoms. The opisthokonts, previousl ...
) or
cycloartenol Cycloartenol is an important triterpenoid of the sterol class which is found in plants. It is the starting point for the synthesis of almost all plant steroids, making them chemically distinct from the steroids of fungi and animals which are instea ...

cycloartenol
(plants). Lanosterol and cycloartenol are derived from the
cyclization A cyclic compound (''ring compound'') is a term for a chemical compound, compound in the field of chemistry in which one or more series of atoms in the compound is connected to form a Ring (chemistry), ring. Rings may vary in size from three to many ...
of the
triterpene Triterpenes are a class of chemical compounds composed of three units with the molecular formula C30H48; they may also be thought of as consisting of six . Animals, plants and fungi all produce triterpenes, including , the precursor to all s. St ...
squalene Squalene is an organic compound. With the formula (C5H8)6, it is a triterpene. It is a colourless oil although impure samples appear yellow. It was originally obtained from shark liver oil (hence its name, as ''Squalus'' is a genus of sharks). All ...

squalene
. The steroid core structure is typically composed of seventeen
carbon Carbon (from la, carbo "coal") is a with the C and 6. It is lic and —making four s available to form s. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 percent of Earth's crust. Three occur naturally, ...

carbon
atoms, bonded in four "
fused Fuse or FUSE may refer to: Devices * Fuse (electrical), a device used in electrical systems to protect against excessive current ** Fuse (automotive), a class of fuses for vehicles * Fuse (hydraulic), a device used in hydraulic systems to protect ...
" rings: three six-member
cyclohexane Cyclohexane is a cycloalkane with the molecular formula C6H12. Cyclohexane is non-polar. Cyclohexane is a colorless, flammable liquid with a distinctive detergent-like odor, reminiscent of cleaning products (in which it is sometimes used). Cycloh ...

cyclohexane
rings (rings A, B and C in the first illustration) and one five-member
cyclopentane Cyclopentane (also called C pentane) is a highly flammable , Germany Image:Tu braunschweig 750 grad ofen.jpg, 250px, Germany, German test apparatus for determining combustibility at Technische Universität Braunschweig A combustible material is ...

cyclopentane
ring (the D ring). Steroids vary by the
functional groups In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the r ...
attached to this four-ring core and by the
oxidation state The oxidation state, or oxidation number, is the hypothetical charge Charge or charged may refer to: Arts, entertainment, and media Films * ''Charge, Zero Emissions/Maximum Speed'', a 2011 documentary Music * Charge (David Ford album), ''Charge ...
of the rings.
Sterol Sterol is an organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains with other carbon s), millions of organic compounds are known. The study of the properties, reactions, and synth ...

Sterol
s are forms of steroids with a
hydroxy group A hydroxy or hydroxyl group is a functional group with the chemical formula -OH and composed of one oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen Group ( ...
at position three and a skeleton derived from
cholestane Cholestane is a saturated tetracyclic triterpene. This carbon-27 biomarker is produced by diagenesis Diagenesis () is the process that describes physical and chemical changes in sediments first caused by water-rock interactions, microbial ac ...

cholestane
. ''Also available with the same authors at'' ; ''Also available online at'' Steroids can also be more radically modified, such as by changes to the ring structure, for example,
cutting Cutting is the separation or opening of a physical object, into two or more portions, through the application of an acutely directed force. Implements commonly used for wikt:cut, cutting are the knife and saw, or in medicine and science the scal ...
one of the rings. Cutting Ring B produces
secosteroid A secosteroid () is a type of steroid with a "broken" ring. The word ''secosteroid ''derives from the Latin verb ''secare'' meaning "to cut", and 'steroid'. Secosteroids are alternatively described as a subclass of steroids; ; or derived from st ...
s one of which is
vitamin D3
vitamin D<sub>3</sub>
. Examples include the
lipid In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...
cholesterol Cholesterol is any of a class of certain organic compound, organic molecules. A cholesterol is a sterol (or chemical modification, modified steroid), a type of lipid. Cholesterol is biosynthesis, biosynthesized by all animal Cell (biology)#Euk ...

cholesterol
, the sex hormones
estradiol Estradiol (E2), also spelled oestradiol, is an estrogen steroid hormone and the major female sex hormone. It is involved in the regulation of the estrous cycle, estrous and menstrual cycle, menstrual female reproductive cycles. Estradiol is resp ...

estradiol
and
testosterone Testosterone is the primary sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two cl ...
, and the
anti-inflammatoryAnti-inflammatory (or antiinflammatory) is the property of a substance or treatment that reduces inflammation or swelling. Anti-inflammatory drugs make up about half of analgesics, remedying pain by reducing inflammation as opposed to opioids, whic ...
drug
dexamethasone Dexamethasone is a used to treat , a number of s, severe , , , , , eye pain following , (a complication of some forms of cancer), and along with s in . In , it may be used in combination with a medication such as . In , it may be used to imp ...

dexamethasone
.


Nomenclature

Gonane Gonane is a chemical compound with formula , whose molecule can be described as three molecules of cyclohexane Cyclohexane is a cycloalkane with the molecular formula C6H12. Cyclohexane is non-polar. Cyclohexane is a colorless, flammable liqu ...

Gonane
, also known as steran or cyclopentanoperhydrophenanthrene, the simplest steroid and the nucleus of all steroids and sterols, is composed of seventeen
carbon Carbon (from la, carbo "coal") is a with the C and 6. It is lic and —making four s available to form s. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 percent of Earth's crust. Three occur naturally, ...

carbon
atoms in carbon-carbon bonds forming four fused rings in a three-dimensional shape. The three
cyclohexane Cyclohexane is a cycloalkane with the molecular formula C6H12. Cyclohexane is non-polar. Cyclohexane is a colorless, flammable liquid with a distinctive detergent-like odor, reminiscent of cleaning products (in which it is sometimes used). Cycloh ...

cyclohexane
rings (A, B, and C in the first illustration) form the skeleton of a
perhydro
perhydro
derivative of
phenanthrene Phenanthrene is a likely carcinogenic compound that poses a large toxicity risk to exposed living organisms. However, according to IARC, it is not identified as probable, possible or confirmed human carcinogen. It is a polycyclic aromatic hydroca ...

phenanthrene
. The D ring has a
cyclopentane Cyclopentane (also called C pentane) is a highly flammable , Germany Image:Tu braunschweig 750 grad ofen.jpg, 250px, Germany, German test apparatus for determining combustibility at Technische Universität Braunschweig A combustible material is ...

cyclopentane
structure. When the two methyl groups and eight carbon
side chain In organic chemistry Organic chemistry is a branch of chemistry that studies the structure, properties and reactions of organic compounds, which contain carbon in covalent bonding.Clayden, J.; Greeves, N. and Warren, S. (2012) ''Organic Chemis ...
s (at C-17, as shown for cholesterol) are present, the steroid is said to have a cholestane framework. The two common 5α and 5β stereoisomeric forms of steroids exist because of differences in the side of the largely planar ring system where the hydrogen (H) atom at carbon-5 is attached, which results in a change in steroid A-ring conformation. Isomerisation at the C-21 side chain produces a parallel series of compounds, referred to as isosteroids. Examples of steroid structures are: File:Testosteron.svg, alt=Chemical diagram,
Testosterone Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...
, the principal male
sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typically made in the ...
and an
anabolic steroid Anabolic steroids, also known more properly as anabolic–androgenic steroids (AAS), are steroid A steroid is a biologically active organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability t ...
File:Cholsäure.svg, alt=Chemical diagram,
Cholic acid Cholic acid, also known as 3α,7α,12α-trihydroxy-5β-cholan-24-oic acid is a primary bile acid that is insoluble in water (soluble in ethanol, alcohol and acetic acid), it is a white crystalline substance. Salts of cholic acid are called cholat ...

Cholic acid
, a
bile acid Bile acids are steroid acids found predominantly in the bile of mammals and other vertebrates. Diverse bile acids are synthesized in the liver. Bile acids are conjugated with taurine or glycine residues to give anions called bile salts. Primary b ...
, showing the
carboxylic acid A carboxylic acid is an organic acid that contains a carboxyl group (C(=O)OH) attached to an R-group. The general formula of a carboxylic acid is R−COOH or R−CO2H, with substituent, R referring to the alkyl, alkenyl, aryl, or other group. ...
and additional
hydroxyl group A hydroxy or hydroxyl group is a functional group with the chemical formula -OH and composed of one oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the ...

hydroxyl group
s often present File:Dexamethasone structure.svg, alt=Chemical diagram,
Dexamethasone Dexamethasone is a used to treat , a number of s, severe , , , , , eye pain following , (a complication of some forms of cancer), and along with s in . In , it may be used in combination with a medication such as . In , it may be used to imp ...

Dexamethasone
, a synthetic
corticosteroid Corticosteroids are a class of steroid hormone A steroid hormone is a steroid , hypothetical a steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is shown with IUPAC The International Union of Pure a ...
drug File:Lanosterin.svg, alt=Chemical diagram,
Lanosterol Lanosterol is a tetracyclic triterpenoid Triterpenes are a class of chemical compounds composed of three terpene units with the molecular formula C30H48; they may also be thought of as consisting of six isoprene units. Animals, plants and fungi a ...

Lanosterol
, the
biosyntheticBiosynthesis is a multi-step, enzyme-Catalysis, catalyzed process where substrate (chemistry), substrates are converted into more complex Product (chemistry), products in living organisms. In biosynthesis, simple Chemical compound, compounds are modi ...
precursor to animal steroids. The number of carbons (30) indicates its
triterpenoid Triterpenes are a class of chemical compounds composed of three terpene units with the molecular formula C30H48; they may also be thought of as consisting of six isoprene units. Animals, plants and fungi all produce triterpenes, including squalene ...
classification. File:Progesteron.svg, alt=Chemical diagram,
Progesterone Progesterone (P4) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell (biology), cell. Endogenous substances and processes contrast with exo ...

Progesterone
, a steroid hormone involved in the female menstrual cycle, pregnancy, and embryogenesis File:Medrogestone.png, alt=Chemical diagram,
Medrogestone Medrogestone, sold under the brand name Colprone among others, is a progestin A progestogen, also referred to as a progestagen, gestagen, or gestogen, is a type of medication which produces effects similar to those of the natural product, natura ...

Medrogestone
, a synthetic drug with effects similar to progesterone File:Sitosterol structure.svg, alt=Chemical diagram, , a plant or
phytosterol Phytosterols are phytosteroids, similar to cholesterol, that serve as structural components of biological membranes of plants. They encompass plant sterols and stanol ester, stanols. More than 250 sterols and related compounds have been identified. ...

phytosterol
, with a fully branched hydrocarbon side chain at C-17 and an hydroxyl group at C-3
In addition to the ring scissions (cleavages), expansions and contractions (cleavage and reclosing to a larger or smaller rings)—all variations in the carbon-carbon bond framework—steroids can also vary: * in the
bond orderBond order, as introduced by Linus Pauling, is defined as the difference between the number of Bonding molecular orbital, bonds and Antibonding molecular orbital, anti-bonds. The bond number itself is the number of electron pairs (bonds) between a p ...
s within the rings, * in the number of methyl groups attached to the ring (and, when present, on the prominent side chain at C17), * in the functional groups attached to the rings and side chain, and * in the
configuration Configuration or configurations may refer to: Computing * Computer configuration or system configuration * Configuration file, a software file used to configure the initial settings for a computer program * Configurator, also known as choice board, ...
of groups attached to the rings and chain. For instance,
sterol Sterol is an organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and t ...

sterol
s such as cholesterol and lanosterol have a
hydroxyl group A hydroxy or hydroxyl group is a functional group with the chemical formula -OH and composed of one oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the ...

hydroxyl group
attached at position C-3, while
testosterone Testosterone is the primary sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two cl ...
and
progesterone Progesterone (P4) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell (biology), cell. Endogenous substances and processes contrast with exo ...

progesterone
have a carbonyl (oxo substituent) at C-3; of these,
lanosterol Lanosterol is a tetracyclic triterpenoid Triterpenes are a class of chemical compounds composed of three terpene units with the molecular formula C30H48; they may also be thought of as consisting of six isoprene units. Animals, plants and fungi a ...

lanosterol
alone has two methyl groups at C-4 and cholesterol (with a C-5 to C-6 double bond) differs from testosterone and progesterone (which have a C-4 to C-5 double bond).


Species distribution and function

In
eukaryote Eukaryotes () are organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interact ...

eukaryote
s, steroids are found in fungi, animals, and plants.


Fungal steroids

Fungal steroids include the
ergosterol Ergosterol (ergosta-5,7,22-trien-3β-ol) is a sterol Sterol is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one ...

ergosterol
s, which are involved in maintaining the integrity of the fungal cellular membrane. Various antifungal drugs, such as
amphotericin B Amphotericin B is an antifungal medication An antifungal medication, also known as an antimycotic medication, is a pharmaceutical A medication (also referred to as medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug ...
and
azole antifungals Azoles are a class of five-membered heterocyclic 125px, Pyridine, a heterocyclic compound A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different chemical element, elements as members of its ring(s ...
, utilize this information to kill
pathogenic In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, ...
fungi. Fungi can alter their ergosterol content (e.g. through loss of function mutations in the enzymes
ERG3 ERG3 or Sterol C-5 desaturase is a fungal enzyme originally from ''Saccharomyces cerevisiae'', the human ortholog of ERG3 is Sterol-C5-desaturase-like, SC5D. ERG3 localizes to both the endoplasmic reticulum and vesicle (biology and chemistry), vesic ...
or ERG6, inducing depletion of ergosterol, or mutations that decrease the ergosterol content) to develop resistance to drugs that target ergosterol. Ergosterol is analogous to the
cholesterol Cholesterol is any of a class of certain organic compound, organic molecules. A cholesterol is a sterol (or chemical modification, modified steroid), a type of lipid. Cholesterol is biosynthesis, biosynthesized by all animal Cell (biology)#Euk ...

cholesterol
found in the cellular membranes of animals (including humans), or the
phytosterols Phytosterols are phytosteroid Phytosteroids, also known as plant steroids, are naturally occurring steroid , a steroid with 27 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is shown with IUPAC The International Un ...
found in the cellular membranes of plants. All mushrooms contain large quantities of ergosterol, in the range of tens to hundreds of milligrams per 100 grams of dry weight. Oxygen is necessary for the synthesis of
ergosterol Ergosterol (ergosta-5,7,22-trien-3β-ol) is a sterol Sterol is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one ...

ergosterol
in fungi. Ergosterol is responsible for the
vitamin D Vitamin D is a group of fat-soluble secosteroid 250px, The parent steroid skeleton. The B-ring of the parent steroid is broken between C9 and C10 to yield D vitamins. A secosteroid () is a type of steroid , hypothetical a steroid with ...
content found in mushrooms; ergosterol is chemically converted into provitamin D2 by exposure to
ultraviolet light Ultraviolet (UV) is a form of electromagnetic radiation with wavelength In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural s ...
. Provitamin D2 spontaneously forms vitamin D2. However, not all fungi utilize ergosterol in their cellular membranes; for example, the pathogenic fungal species ''
Pneumocystis jirovecii ''Pneumocystis jirovecii'' (previously ''P. carinii'') is a yeast-like fungus A fungus (plural: fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), m ...
'' does not, which has important clinical implications (given the mechanism of action of many antifungal drugs). Using the fungus ''
Saccharomyces cerevisiae ''Saccharomyces cerevisiae'' () is a species of yeast Yeasts are eukaryotic Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are ...

Saccharomyces cerevisiae
'' as an example, other major steroids include ergosta‐5,7,22,24(28)‐tetraen‐3β‐ol, , and
lanosterol Lanosterol is a tetracyclic triterpenoid Triterpenes are a class of chemical compounds composed of three terpene units with the molecular formula C30H48; they may also be thought of as consisting of six isoprene units. Animals, plants and fungi a ...

lanosterol
. ''S. cerevisiae'' utilizes 5,6‐dihydroergosterol in place of ergosterol in its cell membrane.


Animal steroids

Animal steroids include compounds of
vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functions as an indiv ...
and
insect Insects (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be in ...

insect
origin, the latter including
ecdysteroid Ecdysteroids are arthropod Steroid hormone, steroid hormones that are mainly responsible for Moulting, molting, development and, to a lesser extent, reproduction; examples of ecdysteroids include ecdysone, ecdysterone, turkesterone and 2-deoxyecdys ...
s such as
ecdysterone 20-Hydroxyecdysone (ecdysterone or 20E) is a naturally occurring ecdysteroid hormone which controls the ecdysis (moulting) and metamorphosis of arthropods. It is therefore one of the most common moulting hormones in insects, crabs, etc. It is also ...
(controlling molting in some species). Vertebrate examples include the
steroid hormones A steroid hormone is a steroid , a steroid with 27 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is shown with IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of ...
and cholesterol; the latter is a structural component of
cell membranes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane A biological membrane, biomembrane or cell membrane is a selectively permeable membra ...
which helps determine the fluidity of
cell membranes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane A biological membrane, biomembrane or cell membrane is a selectively permeable membra ...
and is a principal constituent of (implicated in
atherosclerosis Atherosclerosis is a disease in which the wall of the artery An artery (plural arteries) () is a blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels tr ...

atherosclerosis
). Steroid hormones include: *
Sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typically made in the ...
s, which influence
sex differences Sexual dimorphism is the condition where the two sexes of the same species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A spec ...
and support
reproduction Reproduction (or procreation or breeding) is the biological process Biological processes are those processes that are vital for an organism In biology, an organism () is any organic, life, living system that functions as an indivi ...

reproduction
. These include
androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone A steroid hormone is a steroid , hypothetical a steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 c ...
s,
estrogen Estrogens or oestrogens, are a class of natural or synthetic s responsible for the development and regulation of the female and s. There are three major estrogens that have estrogenic hormonal activity: (E1), (E2), and (E3). Estradiol, an ...

estrogen
s, and
progestogen Progestogens, also sometimes written progestagens or gestagens, are a class of natural or synthetic steroid hormone A steroid hormone is a steroid , hypothetical a steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 c ...
s. *
Corticosteroid Corticosteroids are a class of steroid hormone A steroid hormone is a steroid A steroid is a biologically active organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains w ...
s, including most synthetic steroid drugs, with
natural product A natural product is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together b ...
classes the
glucocorticoid Glucocorticoids (or, less commonly, glucocorticosteroids) are a class of corticosteroid Corticosteroids are a class of steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: cor ...
s (which regulate many aspects of
metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities A bubble of exhaled gas in water In common usage and classical mechanics, a phys ...

metabolism
and
immune function The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as Tumor immunology, cancer cells and objects such as ...
) and the
mineralocorticoid Mineralocorticoids are a class of corticosteroids, which in turn are a class of steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typically made in the adren ...
s (which help maintain blood volume and control
renal The kidneys are two reddish-brown bean-shaped organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly categorized ...

renal
excretion of
electrolyte An electrolyte is a medium containing ions that is electrically conducting Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that quantifies how strongly it resis ...

electrolyte
s) *
Anabolic steroid Anabolic steroids, also known more properly as anabolic–androgenic steroids (AAS), are steroid A steroid is a biologically active organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability t ...
s,
natural Nature, in the broadest sense, is the natural, physical, material world or universe The universe ( la, universus) is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and ...
and synthetic, which interact with androgen receptors to increase muscle and bone synthesis. In popular use, the term "steroids" often refers to anabolic steroids.


Plant steroids

Plant steroids include steroidal
alkaloid Alkaloids are a class of basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming language In computer science Computer science deals with the theoretical foundations of ...
s found in
Solanaceae The Solanaceae , or nightshades, are a family (biology), family of flowering plants that ranges from annual and perennial herbs to vines, lianas, epiphytes, shrubs, and trees, and includes a number of agricultural crops, medicinal plants, spice ...
and
Melanthiaceae Melanthiaceae, also called the bunchflower family, is a family of flowering herbaceous perennial plants native to the Northern Hemisphere. Along with many other lilioid monocots, early authors considered members of this family to belong to ...
(specially the genus
Veratrum ''Veratrum'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer to a ...

Veratrum
),
cardiac glycoside Cardiac glycosides are a class of organic compounds that increase the output force of the heart and decrease its rate of contractions by acting on the cellular sodium-potassium ATPase pump. Their beneficial medical uses are as treatments for conges ...
s, the
phytosterol Phytosterols are phytosteroids, similar to cholesterol, that serve as structural components of biological membranes of plants. They encompass plant sterols and stanol ester, stanols. More than 250 sterols and related compounds have been identified. ...

phytosterol
s and the
brassinosteroid Brassinosteroids (BRs) are a class of polyhydroxysteroids that have been recognized as a sixth class of plant hormones Plant hormones (or phytohormones) are signal molecule In biology, cell signaling (cell signalling in British English), or ce ...
s (which include several plant hormones).


Prokaryotes

In
prokaryotes A prokaryote () is a single-celled organism A unicellular organism, also known as a single-celled organism, is an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contig ...

prokaryotes
, biosynthetic pathways exist for the tetracyclic steroid framework (e.g. in
mycobacteria ''Mycobacterium'' is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles that underlie such classification. The term may also refer ...
) – where its origin from
eukaryote Eukaryotes () are organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interact ...

eukaryote
s is conjectured – and the more-common pentacyclic triterpinoid framework.


Types


By function

The major classes of
steroid hormones A steroid hormone is a steroid , a steroid with 27 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is shown with IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of ...
, with prominent members and examples of related functions, are: *
Corticosteroid Corticosteroids are a class of steroid hormone A steroid hormone is a steroid A steroid is a biologically active organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains w ...
s: ** Glucocorticoids: *** Cortisol, a
glucocorticoid Glucocorticoids (or, less commonly, glucocorticosteroids) are a class of corticosteroid Corticosteroids are a class of steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: cor ...
whose functions include immunosuppression ** Mineralocorticoids: *** Aldosterone, a
mineralocorticoid Mineralocorticoids are a class of corticosteroids, which in turn are a class of steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes: corticosteroids (typically made in the adren ...
which helps regulate blood pressure through water and electrolyte balance * Sex steroids: ** Progestogens: ***
Progesterone Progesterone (P4) is an endogenous Endogenous substances and processes are those that originate from within a system such as an organism, Tissue (biology), tissue, or Cell (biology), cell. Endogenous substances and processes contrast with exo ...

Progesterone
, which regulates cyclical changes in the endometrium of the uterus and maintains a pregnancy ** Androgens: ***
Testosterone Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of Male reproductive system, male reproductive tissues such as testes and prostate, as well as promoting secondar ...
, which contributes to the development and maintenance of male secondary sex characteristics ** Estrogens: *** Estradiol, which contributes to the development and maintenance of female secondary sex characteristics Additional classes of steroids include: * Neurosteroids such as and allopregnanolone * Aminosteroid neuromuscular blocking agents such as pancuronium bromide As well as the following class of
secosteroid A secosteroid () is a type of steroid with a "broken" ring. The word ''secosteroid ''derives from the Latin verb ''secare'' meaning "to cut", and 'steroid'. Secosteroids are alternatively described as a subclass of steroids; ; or derived from st ...
s (open-ring steroids): * Vitamin D forms such as ergocalciferol, cholecalciferol, and calcitriol


By structure


Intact ring system

Steroids can be classified based on their chemical composition. One example of how Medical Subject Headings, MeSH performs this classification is available at the Wikipedia MeSH catalog. Examples of this classification include: The gonane (steroid nucleus) is the parent 17-carbon tetracyclic hydrocarbon molecule with no alkyl sidechains.


Cleaved, contracted, and expanded rings

Secosteroids (Latin ''seco'', "to cut") are a subclass of steroidal compounds resulting, Biosynthesis, biosynthetically or conceptually, from scission (cleavage) of parent steroid rings (generally one of the four). Major secosteroid subclasses are defined by the steroid carbon atoms where this scission has taken place. For instance, the prototypical secosteroid cholecalciferol, (shown), is in the 9,10-secosteroid subclass and derives from the cleavage of carbon atoms C-9 and C-10 of the steroid B-ring; 5,6-secosteroids and 13,14-steroids are similar. Norsteroids (nor-, L. ''norma''; "normal" in chemistry, indicating carbon removal) and homosteroids (homo-, Greek ''homos''; "same", indicating carbon addition) are structural subclasses of steroids formed from biosynthetic steps. The former involves enzymic ring expansion, ring expansion-contraction reactions, and the latter is accomplished (biomimetic synthesis, biomimetically) or (more frequently) through ring closures of open-chain compound, acyclic precursors with more (or fewer) ring atoms than the parent steroid framework. Combinations of these ring alterations are known in nature. For instance, Sheep, ewes who graze on Veratrum, corn lily ingest cyclopamine (shown) and veratramine, two of a sub-family of steroids where the C- and D-rings are contracted and expanded respectively via a biosynthesis, biosynthetic migration of the original C-13 atom. Ingestion of these C-nor-D-homosteroids results in birth defects in lambs: cyclopia from cyclopamine and leg deformity from veratramine. A further C-nor-D-homosteroid (nakiterpiosin) is excreted by Okinawan cyanobacteria, cyanobacteriosponges. e.g., ''Terpios hoshinota'', leading to coral mortality from black coral disease. Nakiterpiosin-type steroids are active against the signaling pathway involving the smoothened and hedgehog (cell signaling), hedgehog proteins, a pathway which is hyperactive in a number of cancers.


Biological significance

Steroids and their metabolites often function as signal transduction, signalling molecules (the most notable examples are steroid hormones), and steroids and phospholipids are components of
cell membrane cell membrane vs. Prokaryotes A prokaryote is a typically unicellular organism that lacks a nuclear membrane-enclosed cell nucleus, nucleus. The word ''prokaryote'' comes from the Greek language, Greek (, 'before') and (, 'nut' or 'kernel').C ...

cell membrane
s. Steroids such as cholesterol decrease
membrane fluidityIn biology, membrane fluidity refers to the viscosity The viscosity of a fluid is a measure of its drag (physics), resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup ...
. Similar to
lipid In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanis ...
s, steroids are highly concentrated energy stores. However, they are not typically sources of energy; in mammals, they are normally metabolized and excreted. Steroids play critical roles in a number of disorders, including malignancies like prostate cancer, where steroid production inside and outside the tumour promotes cancer cell aggressiveness.


Biosynthesis and metabolism

The hundreds of steroids found in animals, fungi, and
plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel ...

plant
s are made from
lanosterol Lanosterol is a tetracyclic triterpenoid Triterpenes are a class of chemical compounds composed of three terpene units with the molecular formula C30H48; they may also be thought of as consisting of six isoprene units. Animals, plants and fungi a ...

lanosterol
(in animals and fungi; see examples above) or
cycloartenol Cycloartenol is an important triterpenoid of the sterol class which is found in plants. It is the starting point for the synthesis of almost all plant steroids, making them chemically distinct from the steroids of fungi and animals which are instea ...

cycloartenol
(in other eukaryotes). Both lanosterol and cycloartenol derive from
cyclization A cyclic compound (''ring compound'') is a term for a chemical compound, compound in the field of chemistry in which one or more series of atoms in the compound is connected to form a Ring (chemistry), ring. Rings may vary in size from three to many ...
of the triterpene, triterpenoid
squalene Squalene is an organic compound. With the formula (C5H8)6, it is a triterpene. It is a colourless oil although impure samples appear yellow. It was originally obtained from shark liver oil (hence its name, as ''Squalus'' is a genus of sharks). All ...

squalene
. Lanosterol and cycloartenol are sometimes called protosterols because they serve as the starting compounds for all other steroids. Steroid biosynthesis is an anabolism, anabolic pathway which produces steroids from simple precursors. A unique biosynthetic pathway is followed in animals (compared to many other organisms), making the pathway a common target for antibiotics and other anti-infection drugs. Steroid metabolism in humans is also the target of cholesterol-lowering drugs, such as statins. In humans and other animals the biosynthesis of steroids follows the mevalonate pathway, which uses acetyl-CoA as building blocks for dimethylallyl pyrophosphate, dimethylallyl diphosphate (DMAPP) and isopentenyl pyrophosphate, isopentenyl diphosphate (IPP). In subsequent steps DMAPP and IPP conjugate to form Farnesyl pyrophosphate, farnesyl diphosphate (FPP), which further conjugates with each other to form the linear triterpenoid squalene. Squalene biosynthesis is catalyzed by Farnesyl-diphosphate farnesyltransferase, squalene synthase, which belongs to the squalene/phytoene synthase family. Subsequent Epoxide, epoxidation and cyclization of squalene generate lanosterol, which is the starting point for additional modifications into other steroids (steroidogenesis). In other eukaryotes, the cyclization product of epoxidized squalene (oxidosqualene) is cycloartenol.


Mevalonate pathway

The mevalonate pathway (also called HMG-CoA reductase pathway) begins with acetyl-CoA and ends with dimethylallyl pyrophosphate, dimethylallyl diphosphate (DMAPP) and isopentenyl pyrophosphate, isopentenyl diphosphate (IPP). DMAPP and IPP donate isoprene units, which are assembled and modified to form terpenes and terpenoid, isoprenoids (a large class of lipids, which include the carotenoids and form the largest class of plant
natural product A natural product is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together b ...
s. Here, the isoprene units are joined to make
squalene Squalene is an organic compound. With the formula (C5H8)6, it is a triterpene. It is a colourless oil although impure samples appear yellow. It was originally obtained from shark liver oil (hence its name, as ''Squalus'' is a genus of sharks). All ...

squalene
and folded into a set of rings to make
lanosterol Lanosterol is a tetracyclic triterpenoid Triterpenes are a class of chemical compounds composed of three terpene units with the molecular formula C30H48; they may also be thought of as consisting of six isoprene units. Animals, plants and fungi a ...

lanosterol
. Lanosterol can then be converted into other steroids, such as cholesterol and
ergosterol Ergosterol (ergosta-5,7,22-trien-3β-ol) is a sterol Sterol is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one ...

ergosterol
. Two classes of medication, drugs target the mevalonate pathway: statins (like rosuvastatin), which are used to reduce hypercholesterolemia, elevated cholesterol levels, and bisphosphonates (like zoledronate), which are used to treat a number of bone-degenerative diseases.


Steroidogenesis

Steroidogenesis is the biological process by which steroids are generated from cholesterol and changed into other steroids. The metabolic pathway, pathways of steroidogenesis differ among species. The major classes of steroid hormones, as noted above (with their prominent members and functions), are the Progestogen,
Corticosteroid Corticosteroids are a class of steroid hormone A steroid hormone is a steroid A steroid is a biologically active organic compound In , organic compounds are generally any s that contain - . Due to carbon's ability to (form chains w ...
s (corticoids), Androgens, and Estrogens. Human steroidogenesis of these classes occurs in a number of locations: *Progestogens are the precursors of all other human steroids, and all human tissues which produce steroids must first convert cholesterol to pregnenolone. This conversion is the rate-limiting step of steroid synthesis, which occurs inside the mitochondrion of the respective tissue. *Cortisol, corticosterone, aldosterone, and testosterone are produced in the adrenal cortex. *Estradiol, estrone and progesterone are made primarily in the ovary, estriol in placenta during pregnancy, and
testosterone Testosterone is the primary sex hormone Sex hormones, also known as sex steroids, gonadocorticoids and gonadal steroids, are steroid hormone A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two cl ...
primarily in the testes (some testosterone is also produced in the adrenal cortex). *Estradiol is converted from testosterone directly (in males), or via the primary pathway DHEA - androstenedione - estrone and secondarily via testosterone (in females). *Stromal cells have been shown to produce steroids in response to signaling produced by androgen-starved prostate cancer cells. *Some neurons and glia in the central nervous system (CNS) express the enzymes required for the local synthesis of pregnenolone, progesterone, DHEA and DHEAS, de novo synthesis, ''de novo'' or from peripheral sources.


Alternative pathways

In plants and bacteria, the non-mevalonate pathway (MEP pathway) uses Pyruvic acid, pyruvate and glyceraldehyde 3-phosphate as substrates to produce IPP and DMAPP. During diseases pathways otherwise not significant in healthy humans can become utilized. For example, in one form of congenital adrenal hyperplasia a congenital adrenal hyperplasia due to 21-hydroxylase deficiency, deficiency in the 21-hydroxylase enzymatic pathway leads to an excess of 17α-Hydroxyprogesterone (17-OHP) – this pathological excess of 17-OHP in turn may be converted to dihydrotestosterone (DHT, a potent androgen) through among others CYP17A1, 17,20 Lyase (a member of the cytochrome P450 family of enzymes), 5α-Reductase and 3α-Hydroxysteroid dehydrogenase.


Catabolism and excretion

Steroids are primarily oxidized by cytochrome P450, cytochrome P450 oxidase enzymes, such as CYP3A4. These reactions introduce oxygen into the steroid ring, allowing the cholesterol to be broken up by other enzymes into bile acids. These acids can then be eliminated by secretion from the liver in bile. The expression of the oxidase gene can be Downregulation and upregulation, upregulated by the steroid sensor PXR when there is a high blood concentration of steroids. Steroid hormones, lacking the side chain of cholesterol and bile acids, are typically Hydroxylation, hydroxylated at various ring positions or 17-ketosteroid, oxidized at the 17 position, Conjugated system, conjugated with sulfate or glucuronic acid and excreted in the urine.


Isolation, structure determination, and methods of analysis

Steroid ''isolation'', depending on context, is the isolation of chemical matter required for chemical structure elucidation, derivitzation or degradation chemistry, biological testing, and other research needs (generally milligrams to grams, but often more or the isolation of "analytical quantities" of the substance of interest (where the focus is on identifying and quantifying the substance (for example, in biological tissue or fluid). The amount isolated depends on the analytical method, but is generally less than one microgram. The methods of isolation to achieve the two scales of product are distinct, but include extraction (chemistry), extraction, precipitation, adsorption, chromatography, and crystallization. In both cases, the isolated substance is purified to chemical homogeneity; combined separation and analytical methods, such as Liquid chromatography–mass spectrometry, LC-MS, are chosen to be "orthogonal"—achieving their separations based on distinct modes of interaction between substance and isolating matrix—to detect a single species in the pure sample. ''Structure determination'' refers to the methods to determine the chemical structure of an isolated pure steroid, using an evolving array of chemical and physical methods which have included NMR and small-molecule crystallography. ''Methods of analysis'' overlap both of the above areas, emphasizing analytical methods to determining if a steroid is present in a mixture and determining its quantity.


Chemical synthesis

Microbial catabolism of
phytosterol Phytosterols are phytosteroids, similar to cholesterol, that serve as structural components of biological membranes of plants. They encompass plant sterols and stanol ester, stanols. More than 250 sterols and related compounds have been identified. ...

phytosterol
side chain In organic chemistry Organic chemistry is a branch of chemistry that studies the structure, properties and reactions of organic compounds, which contain carbon in covalent bonding.Clayden, J.; Greeves, N. and Warren, S. (2012) ''Organic Chemis ...
s yields C-19 steroids, C-22 steroids, and 17-ketosteroids (i.e. Precursor (chemistry), precursors to adrenocortical hormones and contraceptives). The addition and modification of functional groups is key when producing the wide variety of medications available within this chemical classification. These modifications are performed using conventional organic synthesis and/or biotransformation techniques.


Precursors


Semisynthesis

The semisynthesis of steroids often begins from precursors such as
cholesterol Cholesterol is any of a class of certain organic compound, organic molecules. A cholesterol is a sterol (or chemical modification, modified steroid), a type of lipid. Cholesterol is biosynthesis, biosynthesized by all animal Cell (biology)#Euk ...

cholesterol
,
phytosterol Phytosterols are phytosteroids, similar to cholesterol, that serve as structural components of biological membranes of plants. They encompass plant sterols and stanol ester, stanols. More than 250 sterols and related compounds have been identified. ...

phytosterol
s, or sapogenins. The efforts of Syntex, a company involved in the Mexican barbasco trade, used ''Dioscorea mexicana'' to produce the sapogenin diosgenin in the early days of the synthetic steroid Fine chemical#Pharmaceuticals, pharmaceutical industry.


Total synthesis

Some steroidal hormones are economically obtained only by total synthesis from petrochemicals (e.g. 13-alkyl steroids). For example, the pharmaceutical Norgestrel begins from Methoxy-1-tetralone, a petrochemical derived from phenol.


Research awards

A number of Nobel Prizes have been awarded for steroid research, including: * 1927 (Nobel Prize in Chemistry, Chemistry) Heinrich Otto Wieland — Constitution of bile acids and sterols and their connection to vitamins * 1928 (Chemistry) Adolf Otto Reinhold Windaus — Constitution of sterols and their connection to vitamins * 1939 (Chemistry) Adolf Butenandt and Leopold Ruzicka, Leopold Ružička — Isolation and structural studies of steroid sex hormones, and related studies on higher terpenes * 1950 (Nobel Prize in Physiology or Medicine, Physiology or Medicine) Edward Calvin Kendall, Tadeus Reichstein, and Philip Hench — Structure and biological effects of adrenocortical hormone, adrenal hormones * 1965 (Chemistry) Robert Burns Woodward — In part, for the synthesis of cholesterol, cortisone, and
lanosterol Lanosterol is a tetracyclic triterpenoid Triterpenes are a class of chemical compounds composed of three terpene units with the molecular formula C30H48; they may also be thought of as consisting of six isoprene units. Animals, plants and fungi a ...

lanosterol
* 1969 (Chemistry) Derek Barton and Odd Hassel — Development of the concept of conformation in chemistry, emphasizing the steroid nucleus * 1975 (Chemistry) Vladimir Prelog — In part, for developing methods to determine the stereochemical course of cholesterol biosynthesis from mevalonic acid via
squalene Squalene is an organic compound. With the formula (C5H8)6, it is a triterpene. It is a colourless oil although impure samples appear yellow. It was originally obtained from shark liver oil (hence its name, as ''Squalus'' is a genus of sharks). All ...

squalene


See also

* Adrenal gland * Batrachotoxin * List of steroid abbreviations * List of steroids * Membrane steroid receptor * Pheromone * Reverse cholesterol transport * Steroidogenesis inhibitor * Steroidogenic acute regulatory protein * Steroidogenic enzyme


References


Bibliography

* * * A concise history of the study of steroids. * A review of the history of steroid synthesis, especially biomimetic. * Adrenal steroidogenesis pathway. * * {{Authority control Steroids, Metabolic pathways Wikipedia articles with sections published in WikiJournal of Medicine