Estriol (source code)
= Estriol
<Estriol> is an <estrogen> with three <hydroxy groups> on its <steroid> framework, at positions 3, 16 and 17 in the conventional numbering. The usual compound has the specified $16\alpha,17\beta$ arrangement and molecular formula $\mathrm{C_{18}H_{24}O_3}$. Chemical identity includes this spatial arrangement, rather than only a list of constituent elements.<Estriol in ChEBI>[CHEBI:27974, Definition, Formula and structure]{ref}
The structure provides an illuminating comparison with <estrone>, whose formula is $\mathrm{C_{18}H_{22}O_2}$. The two compounds share an eighteen-carbon framework but differ in functional groups and hydrogen count. Equal carbon count does not make them the same molecule, and a shared <estrogen> classification does not imply equal activity in every assay.
Using the database's average <molar mass> of $288.387\,\mathrm{g\,mol^{-1}}$, an illustrative $1\,\mathrm{nmol}$ sample has mass $288.387\,\mathrm{ng}$ by $m=nM$. This converts amount to mass without predicting a physiological response. A comparison of hormonal effects must additionally specify the experimental system and exposure, rather than infer potency from mass alone.<Estriol in ChEBI>[Formula, Average Mass and estrogen role]{ref}
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