<p>Estrogens are used as part of some oral contraceptives, in estrogen replacement therapy of postmenopausal women, and in hormone therapy for transsexual women.</p>

<p>Like all steroid hormones, estrogens readily diffuse across the cell membrane; inside the cell, they interact with estrogen receptors.<sup class="reference" id="_ref-0">[1]</sup></p>

<h2><span class="mw-headline">Types of estrogen</span></h2>

<p>The three major naturally occurring estrogens in women are estradiol, estriol, and estrone. In the body these are all produced from androgens through actions of enzymes.</p>

<li><a title="MedlinePlus" href="http://en.wikipedia.org/wiki/MedlinePlus">MedlinePlus DrugInfo</a> <em><a class="external text" title="http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a682922.html" rel="nofollow" href="http://www.nlm.nih.gov/medlineplus/druginfo/medmaster/a682922.html">medmaster-a682922</a></em> </li>

<li>Nussey and Whitehead: <em><a class="external text" title="http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&amp;rid=endocrin.TOC&amp;depth=10" rel="nofollow" href="http://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&amp;rid=endocrin.TOC&amp;depth=10">Endocrinology, an integrated approach</a></em>, Taylor and Francis 2001. Free online textbook. </li>

<li>conjugated estrogen </li>

<li>esterified estrogen </li>

<li>estriol </li>

<li>estrone </li>

</ul>