A catechol estrogen is a steroidal estrogen that contains catechol (1,2-dihydroxybenzene) within its structure. The catechol estrogens are endogenous metabolites of estradiol and estrone and include the following compounds:
2-Hydroxylated:
2-Hydroxyestradiol
2-Hydroxyestrone
2-Hydroxyestriol
4-Hydroxylated:
4-Hydroxyestradiol
4-Hydroxyestrone
4-Hydroxyestriol
The most abundant catechol estrogen in serum and urine is 2-hydroxyestrone, with 2-hydroxyestradiol and 2-hydroxyestriol also being formed, while the principal 4-hydroxy catechol estrogen, 4-hydroxyestrone, is present in only small amounts in urine. 4-Hydroxyestriol has been detected in the urine of pregnant women. The catechol estrogens are formed from estradiol and estrone by cytochrome P450 enzymes predominantly in the liver but also in extrahepatic tissues, and are metabolized by catechol O-methyltransferase (COMT) into methoxylated estrogens such as 2-methoxyestradiol and 4-methoxyestrone as well as by conjugation via other phase II enzymes. Under poor conditions of inactivation by phase II enzymes, catechol estrogens can undergo oxidation to reactive quinones and semiquinones, and this has been hypothesized to contribute to estrogen-induced carcinogenesis.
Similarly to estradiol and estrone, catechol estrogens possess estrogenic activity. 2-Hydroxylated catechol estrogens are weak and possibly antiestrogenic estrogens, whereas their 4-hydroxylated counterparts are more potent in their estrogenic activity. For instance, 2-hydroxyestrone reportedly shows negligible uterotrophic effect in animals, whereas 4-hydroxy catechol estrogens show moderate changes in stimulating uterine weight. In addition to being substrates for COMT similarly to catecholamines like dopamine, norepinephrine, and epinephrine, catechol estrogens are potent competitive inhibitors of COMT as well as of tyrosine hydroxylase, and may affect both catecholamine biosynthesis and metabolism.
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2-Hydroxyestradiol (2-OHE2), also known as estra-1,3,5(10)-triene-2,3,17β-triol, is an endogenous steroid, catechol estrogen, and metabolite of estradiol, as well as a positional isomer of estriol. Transformation of estradiol to 2-hydroxyestradiol is a major metabolic pathway of estradiol in the liver. CYP1A2 and CYP3A4 are the major enzymes catalyzing the 2-hydroxylation of estradiol. Conversion of estradiol into 2-hydroxyestradiol has also been detected in the uterus, breast, kidney, brain, and pituitary gland, as well as the placenta, and may similarly be mediated by cytochrome P450 enzymes.
2-Hydroxyestrone (2-OHE1), also known as estra-1,3,5(10)-trien-2,3-diol-17-one, is an endogenous, naturally occurring catechol estrogen and a major metabolite of estrone and estradiol. It is formed irreversibly from estrone in the liver and to a lesser extent in other tissues via 2-hydroxylation mediated by cytochrome P450 enzymes, mainly the CYP3A and CYP1A subfamilies. 2-OHE1 is the most abundant catechol estrogen in the body.
L'estrone ou œstrone (E1), est une hormone œstrogène sécrétée par l'ovaire chez la femme non ménopausée (sous l'influence des hormones FSH et LH), par le placenta en phase de grossesse et, dans une moindre mesure, par les tissus adipeux chez l'homme ou la femme ménopausée. Sa formule brute est C18H22O2. L'estrone a un point de fusion de . L’estrone est également parfois appelée folliculine. L'estrone est synthétisée à partir de l'androstènedione, un dérivé de la progestérone.
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