Lipoidal estradiol (LE2) is the variety of endogenous C17β long-chain

fatty acid In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, ...

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides a ...

s of

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 and menstrual female reproductive cycles. Estradiol is responsible for the development o ...

which are formed as metabolites of estradiol. Important examples of these esters include estradiol arachidonate, estradiol lineolate,

estradiol oleate 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 palmitate, and estradiol stearate. LE2 are

estrogen Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal ac ...

s but do not bind to the

estrogen receptor Estrogen receptors (ERs) are a group of proteins found inside cells. They are receptors that are activated by the hormone estrogen (17β-estradiol). Two classes of ER exist: nuclear estrogen receptors ( ERα and ERβ), which are members of the ...

, instead acting as

prohormone A prohormone is a committed precursor of a hormone consisting of peptide hormones synthesized together that has a minimal hormonal effect by itself because of its expression-suppressing structure, often created by protein folding and binding additi ...

s of estradiol. Relative to estradiol, they have far longer-lasting durations of effect due to their much slower rates of

metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run c ...

and clearance. It has been hypothesized that LE2 may serve as a store of estrogen for when estradiol levels become low. LE2 are highly

lipophilic Lipophilicity (from Greek λίπος "fat" and φίλος "friendly"), refers to the ability of a chemical compound to dissolve in fats, oils, lipids, and non-polar solvents such as hexane or toluene. Such non-polar solvents are themselves lipo ...

and

hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, t ...

and are found in highest concentrations in

adipose tissue Adipose tissue, body fat, or simply fat is a loose connective tissue composed mostly of adipocytes. In addition to adipocytes, adipose tissue contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular ...

and other estrogen-sensitive tissues and in low but detectable concentrations in circulation, with none excreted in

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellular ...

. They have been referred to as the "endogenous counterparts of the synthetic esters of estrogens" like

estradiol valerate Estradiol valerate (EV), sold for use by mouth under the brand name Progynova and Primiwal E4 and for use by injection under the brand names Delestrogen and Progynon Depot among others, is an estrogen medication. It is used in hormone therapy fo ...

and

estradiol cypionate Estradiol cypionate (EC), sold under the brand name Depo-Estradiol among others, is an estrogen medication which is used in hormone therapy for menopausal symptoms and low estrogen levels in cis women, in hormone therapy for trans women, and in ...

. Two of the estradiol esters that compose LE2, estradiol palmitate and estradiol stearate, have been developed and marketed for medical use as long-acting estrogens for use via

depot Depot ( or ) may refer to: Places * Depot, Poland, a village * Depot Island, Kemp Land, Antarctica * Depot Island, Victoria Land, Antarctica * Depot Island Formation, Greenland Brands and enterprises * Maxwell Street Depot, a restaurant in ...

intramuscular injection. Estradiol is esterified into LE2 by lecithin–cholesterol acyltransferase (LCAT).

References

Estradiol esters Estranes Estrogens Human metabolites Prodrugs {{genito-urinary-drug-stub

See also

References