Estriol is a metabolite of estrone metabolized via 16alpha-hydroxyestrone through the agitator 16alpha-hydroxysteroid dehydrogenase or to 2- or 4-hydroxyestrone (catechol estrogens) by the activity of catecho-O-methyltransferase. The closing metabolites can be formed in the academician and may attempt with receptors for catecholamines. Metabolites are conjugated with sulfate or glucuronide afore elimination by the kidney.
During pregnancy, estriol constitutes 60-70% of the absolute estrogens, accretion to 300-500-fold in affiliation to non-pregnant women. The backward appellation animal fetus produces almost ample amounts of 16 alphahydroxy DHEA, which serves the mother as a forerunner of estriol. It has been apparent that 90% of the precursors for the accumulation of estriol are of fetal origin. If aberrant affectionate serum screening results, accurately low levels of unconjugated estriol in the additional trimester are detected, a analysis of Smith-Lemli-Opitz affection (SLOS), or RSH is suspected. SLOS is an autosomal backward ataxia acquired by mutations of the gene encoding 7-dehydrocholesterol reductase.

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