17-Alpha-Estradiol
A non-feminising stereoisomer of estradiol that reproducibly extends lifespan in male (but not female) mice in the NIA Interventions Testing Program. Because it lacks strong classical estrogenic activity, it is of high interest as a geroprotector, but there is essentially no human longevity data.
01 Overview
17-alpha-estradiol is the alpha stereoisomer of the main human estrogen 17-beta-estradiol. It binds estrogen receptors far more weakly and is considered largely non-feminising, historically explored for hair loss and lipid effects.
In aging science it is notable because the NIA Interventions Testing Program found it reliably extended median lifespan in male mice across multiple sites, with little or no effect in females — a striking sex-specific geroprotective signal linked to improved metabolic health, reduced inflammation, and hypothalamic effects rather than classical estrogen signalling. Human data for longevity use are essentially absent; it is not an approved oral drug in most markets for this purpose, and self-experimentation carries unknown risks, including possible estrogenic effects at higher doses. Doses used in mice do not translate directly to humans.
02 Mechanism
Acts largely independently of classical estrogen-receptor feminisation; proposed to improve metabolic health and reduce inflammation via hypothalamic and hepatic effects, producing a male-specific geroprotective response.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Experimental (no established human dose) | 1–5 mg/day | Oral | No validated human longevity dose exists; ranges are speculative extrapolations, not recommendations. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Male-specific lifespan extension (mice)Reproducibly extended lifespan in male mice across multiple ITP sites, with little effect in females. | ~+12% median (male mice) | Preclinical | |
| Improved metabolic markers (animal)Reduced adiposity, improved glucose tolerance, and lowered inflammation in male rodents. | moderate | Preclinical |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Possible estrogenic effects at higher dosesThough marketed as non-feminising, at sufficient doses it may exert estrogenic effects such as gynaecomastia in males. | Moderate | Dose-dependent / uncharacterised | Preclinical | |
| No human safety or efficacy dataThere are no human trials for longevity use, so risks and benefits in people are unknown. | Moderate | Inherent | Unconfirmed |