Wikipedia
Methylestradiol, or 17α-methylestradiol (17α-ME), is a semisynthetic, steroidal estrogen that has been sold in combination with normethandrone (methylestrenolone), a progestin and weak androgen/ anabolic steroid, under brand names including Ginecosid, Ginecoside, Mediol, Renodiol for the treatment of menopausal symptoms in Brazil, Venezuela, and Indonesia. Due to the presence of the 17α-methyl group, methylestradiol cannot be deactivated by oxidation of the 17β-hydroxy group, resulting in improved metabolic stability and potency relative to estradiol analogously to ethinyl estradiol (17α-ethinylestradiol). In addition to its clinical use, methylestradiol has been studied as a radiopharmaceutical.
Methylestradiol is an active metabolite of the anabolic steroid methyltestosterone (17α-methyltestosterone), and is responsible for the estrogenic side effects of the drug such as gynecomastia. Metandienone (17α-methyl-δ-testosterone), another anabolic steroid, produces a similar but non-identical estrogenic metabolite.