Pharmacodynamics<unk>  is an estrogen, or an agonist of the estrogen receptor. It shows somewhat lower affinity for the estrogen receptor than estradiol or ethinylestradiol.<unk>  is an active metabolite of the androgens/anabolic steroids methyltestosterone (17α-methyltestosterone), metandienone (17α-methyl-δ1-testosterone), and normethandrone (17α-methyl-19-nortestosterone), and is responsible for their estrogenic side effects, such as gynecomastia and fluid retention. Relative affinities (%) of<unk>  and related steroids Compound Estradiol 2.6 7.9 100 0.6 0.13 8.7 <0.1 Ethinylestradiol 15–25 1–3 112 1–3 <1 ? ?<unk>  3–10, 15–25 1–3 67 1–3 <1 ? ? Methyltestosterone 3 45, 100–125 ? 1–5 ? 5 ? Normethandrone 100 146 <0.1 1.5 0.6 ? ? Sources: Values are percentages (%). Reference ligands (100%) were progesterone for the , testosterone for the , for the , for the , aldosterone for the , for , and cortisol for . Sources: Pharmacokinetics Due to the presence of its C17α methyl group,<unk>  cannot be deactivated by oxidation of the C17β hydroxyl group, resulting in improved metabolic stability and potency relative to estradiol. This is analogous to the case of ethinylestradiol and its C17α ethynyl group.
Methylestradiol
Progestogen 
Progestogen
Vinyltestosterone
2-Hydroxyestradiol
Methyltestosterone
Ethinylestradiol
Cloxestradiol