Estradiol stearate
Estradiol stearate (brand name Depofollan), or estradiol octadecanoate, is a naturally occurring steroidal estrogen and an estrogen ester – specifically, the C17β stearate ester of estradiol. It occurs in the body as a very long-lasting metabolite and prohormone of estradiol. In addition, estradiol stearate is or has been available as a pharmaceutical drug for use via depot intramuscular injection. The drug was introduced in 1941 as Depofollan and was the first long-acting estrogen, although it has never been widely used. It has been reported in at least one source to have a duration of at least one month.
Pharmacodynamics of estradiol
Lower dosages and concentrations of estradiol can also significantly suppress gonadotropin secretion and testosterone levels in men and transgender women. A retrospective study of oral estradiol monotherapy in transgender women found that dosages of 1 to 8 mg/day increased mean estradiol levels to about 50 to 150 pg/mL and suppressed mean testosterone levels to about 120 to 10 ng/dL. However, there was high interindividual variability in the estradiol and testosterone levels achieved, and testosterone levels were insufficiently suppressed in many even at 8 mg/day. In another study, a dosage of 1 mg/day oral micronized estradiol in healthy older men, which increased circulating estradiol levels by a relatively high amount of 6-fold (to 159 pg/mL), estrone levels by 15-fold (to 386 pg/mL), and SHBG levels by 17%, was found to suppress total testosterone levels by 27% (to 436 ng/dL) and free testosterone levels by 34% (to 11.8 ng/dL). A pharmacodynamic study of testosterone suppression by polyestradiol phosphate in men with prostate cancer found that estradiol levels of about 135 pg/mL (500 pmol/L) would decrease testosterone levels by 50% (from 430 ng/dL to 215 ng/dL), while estradiol levels of about 410 to 545 pg/mL (1500–2000 pmol/L) would decrease testosterone levels well into the castrate range to about 6 to 12 ng/dL (0.2–0.4 nmol/L).