17-alpha-Estradiol

Interventions Testing Program lifespan studies (animal data)

• In the 2009 cohort, published in 2014, 17-alpha-estradiol at 4.8 ppm in food from 10 months of age increased male median lifespan by 12 percent in pooled data, but the gain was 28 percent at UT Health San Antonio and a non-significant 3 percent at The Jackson Laboratory and Michigan; maximum lifespan did not change significantly, and female lifespan was not affected (PMID: 24245565).
• In the 2011 cohort, published in 2016, a threefold higher dose, 14.4 ppm from 10 months of age, increased male median lifespan by 19 percent (P<0.001), with significant gains at all three sites (26, 9 and 23 percent), and raised the age at the 90th percentile of survival by 12 percent; female survival did not change (PMID: 27312235).
• In the 2016 cohort, published in 2021 and limited to males, 14.4 ppm started at 16 or 20 months of age increased male median lifespan by 19 percent (P<0.0001) and 11 percent (P=0.007); the age at the 90th percentile rose 7 percent (P=0.004) with the 16-month start and a non-significant 5 percent (P=0.17) with the 20-month start, and body weight fell about 20 percent after the diets began (PMID: 33788371). Median lifespan with the 16-month start (933 days) was close to that with the 10-month start in the 2016 report (925 days) (PMID: 33788371).

Healthspan studies in mice and rats (animal data)

• In old male mice, 17-alpha-estradiol reduced fasting glucose, visceral fat, insulin, HbA1c and inflammatory markers without feminizing the males (PMID: 26809497), and it improved metabolic measures in male rats (PMID: 33289482).
• Started at 4 months of age, 17-alpha-estradiol preserved muscle mass, fiber size, grip strength and rotarod performance at 25 months in male mice but not in females or castrated males, and similar benefits were seen when treatment started at 16 months (PMID: 30740872).
• In male mice, long-term treatment did not reduce sperm quality or the ability of males to impregnate females (PMID: 35689785).
• In young female C57BL/6J mice, 17-alpha-estradiol prevented the weight gain, fat gain and bone loss that followed ovary removal over 6 weeks (PMID: 33065227), but did not preserve ovarian reserve or female fertility in intact females (PMID: 35032571).

Primate tolerability studies (animal data)

• In rhesus macaques, short-term treatment of male monkeys was tolerated and mildly improved metabolic measures at the higher dose, but both doses caused feminization such as testicular atrophy (PMID: 36897526).
• A short pilot study in male marmosets found no feminization at two dose ranges, with mild, mostly non-significant drops in body mass, fat and HbA1c (PMID: 39107620).

Human trials of topical 17-alpha-estradiol for hair loss

• Orfanos and Vogels (1980) ran a controlled randomized double-blind trial of at least 6 months in 51 patients with androgenetic alopecia and increased hair shedding. With a lotion containing 0.025 percent 17-alpha-estradiol, the share of telogen (resting-phase) hairs fell in 63 percent of treated patients against 37 percent of controls, and the telogen rate rose in 11 percent against 50 percent; growing (anagen) hair counts did not change significantly, and no regrowth of new hair was found (PMID: 7398983).
• Blume-Peytavi and colleagues (2007) led a randomized multicenter phase 4 trial from the Charite in Berlin in 103 women with androgenetic alopecia. Women used 0.025 percent alfatradiol solution once daily for 6 months and then switched to 2 percent minoxidil, or used 2 percent minoxidil twice daily for 12 months. Measured by TrichoScan, minoxidil increased hair thickness and density at 6 months, while these measures stayed nearly unchanged with alfatradiol, and the authors concluded that alfatradiol slows or stabilizes hair loss (PMID: 17451383). BodyHackGuide's minoxidil guide covers the comparison drug.
• Kim and colleagues (2012) ran an 8-month open-label phase 4 study in 53 Korean women aged 18 to 55 with female pattern hair loss. With a 0.025 percent 17-alpha-estradiol solution once daily, hair counts and hair diameter rose from baseline (p<0.0001); the study had no control group (PMID: 22879713).
• In a retrospective study of 119 postmenopausal women by Rossi and colleagues (2020), women treated with topical finasteride 0.5 percent plus minoxidil 2 percent improved more on blinded photographic scoring than women treated with 17-alpha-estradiol 0.05 percent plus minoxidil 2 percent (PMID: 32363101). BodyHackGuide's finasteride guide covers that drug.
• A 2003 review by a Zurich dermatologist described topical 17-alpha-estradiol as an alternative for women with hair loss whose efficacy had not been proven (PMID: 12942187).

Human studies of 17-alpha-estradiol taken by mouth

• In a metabolism study, male volunteers took 17-alpha-estradiol by mouth or under the tongue with a tritium-labeled tracer; after oral intake less than 1 percent of serum 17-alpha-estradiol was free, sublingual intake gave temporarily higher free levels, and phase I metabolism was poor (PMID: 12234624).
• Authors from MIGENIX, which was developing an oral sulfate conjugate of 17-alpha-estradiol as a neuroprotective drug, reported positive safety and pharmacokinetic data from a phase 1 study, but the abstract gave no participant numbers or phase 1 results (PMID: 16024755). A ClinicalTrials.gov search on 27 October 2026 found no registered trial of 17-alpha-estradiol or alfatradiol.

Feminizing effects in animals

At 14.4 ppm in the diet, the dose used in the 2016 and 2021 ITP studies, 17-alpha-estradiol raised uterine weight in ovariectomized mice to the level of intact controls, while the 4.8 ppm dose of the 2014 study did not (PMID: 27312235). In male rhesus macaques given 0.20 or 0.30 mg/kg a day over a relatively short period, 17-alpha-estradiol caused no gastrointestinal distress or blood count changes and mildly improved body mass, fat and HbA1c at the higher dose, but both doses caused feminization such as testicular atrophy, higher circulating estrogens and suppressed androgens and gonadotropins, with a sevenfold rise in serum 17beta-estradiol in the first trial (PMID: 36897526). A short pilot study in male marmosets found no feminization at two dose ranges (PMID: 39107620). In male mice, long-term 17-alpha-estradiol at the dose most used in aging research did not change testis mass, sperm measures, fertility or plasma 17beta-estradiol and mildly raised testosterone (PMID: 35689785). Body weight fell about 20 percent after late-start treatment in male mice (PMID: 33788371).

Female mice (animal data)

17-alpha-estradiol did not extend female lifespan in the ITP (PMID: 24245565, PMID: 27312235), did not preserve ovarian reserve or fertility in female mice (PMID: 35032571), and reduced the number of primordial ovarian follicles in long-lived growth hormone receptor knockout mice but not in normal littermates (PMID: 31698046).

Interactions

No human drug interaction studies of 17-alpha-estradiol were found.