Peptide & experimental
17α-Estradiol (Alfatradiol)
Weakly active estrogen isomer · Alfatradiol, Ell-Cranell alpha
17α-estradiol is one of the most striking results of the American Interventions Testing Program: in three studies, male mice lived longer with it, most recently by 19 percent, even when administration only began at an older age. In Germany the substance has been known for decades as alfatradiol, a hair tonic against hereditary hair loss. As an agent taken by mouth, it has not been studied in humans.
What 17α-estradiol is
17α-estradiol is the mirror image of 17β-estradiol, the most important female sex hormone. The difference lies only in the spatial position of a group at carbon atom 17, but its estrogenic effect is much weaker. In research it is therefore considered a “non-feminizing” estrogen.
Under the name alfatradiol, it has been known in Germany for decades as a solution for the scalp. The longevity interest, by contrast, comes from the Interventions Testing Program (ITP), in which the US aging research institute NIA tests substances in parallel at three sites in genetically heterogeneous mice and publishes all results, including the negative ones. The data on acarbose and rapamycin come from the same program.
How it works
In male mice, 17α-estradiol lowers fat mass, improves insulin sensitivity and preserves the adaptability of liver metabolism. Many of these effects run via estrogen receptor alpha (ERα), among other places in control centers of the hypothalamus; whether genomic or rapid signaling pathways are decisive, and why females do not benefit, is unresolved (Santín-Márquez 2026). An experiment in which ERα was switched off in specific neurons showed that the metabolic benefits do not depend solely on these cells (Camon 2024).
On hair it acts differently: in isolated human hair follicles, 17α-estradiol lowers the formation of dihydrotestosterone and increases the activity of aromatase, which converts testosterone into estrogens (Hoffmann 2002). This is the same hormonal pathway that finasteride also targets, only by a different route.
What is well supported
- Life extension in male mice has been reproduced several times. In the ITP, 17α-estradiol extended the median lifespan of male mice by 12 percent in 2014 (p = 0.002). At triple the dose, it robustly extended median and maximum lifespan in 2016. In 2021 it also worked when started late: plus 19 percent when started at 16 months (p less than 0.0001), plus 11 percent when started at 20 months (p = 0.007).
- The results come from a particularly rigorous testing system. The ITP tests each substance in parallel at three sites and publishes all results. That 17α-estradiol remained positive there across several rounds, doses and starting ages sets it apart from many longevity candidates that were tested in only a single laboratory.
- The metabolic pathway is well described in mice. Less fat mass, better insulin sensitivity, preserved liver metabolism, mediated largely via ERα – this has been shown in numerous mouse studies and summarized in a 2026 review.
- On the scalp it has long been in use. In a controlled, double-blind study with 51 patients, the proportion of shedding hairs fell in 63 percent under a 17α-estradiol hair tonic and in 37 percent under control; no side effects were observed (Orfanos 1980).
What the studies show
ITP 2014: plus 12 percent in males
Harrison and colleagues tested four substances in genetically heterogeneous mice at three sites. 17α-estradiol extended the median lifespan of males by 12 percent; maximum lifespan was not significantly extended. The effect was markedly stronger at one site than at the other two and could not be explained by body weight. Females did not live longer.
ITP 2016: higher dose, stronger effect
In the follow-up study, the triple dose robustly extended both median and maximum lifespan of male mice, again only in males. The authors see this as an indication of how important dose finding is in lifespan studies (Strong 2016).
ITP 2021: even when started late
When administration began only at 16 months, 17α-estradiol extended the median lifespan of male mice by 19 percent, and by 11 percent when started at 20 months. The 90th percentile of lifespan rose by 7 and 5 percent, the latter not significant. Body weight fell by about 20 percent after the start (Harrison 2021).
Marmosets 2025: first steps toward primates
A short pilot study in male marmosets tested two doses for tolerability. There were no gastrointestinal complaints, no changes in vital signs and no feminization. Body weight, fat percentage and HbA1c fell slightly, mostly without significance (Sathiaseelan 2025). The authors see this as groundwork for later human studies.
Hair loss: two studies in humans
In the double-blind study by Orfanos 1980, a 17α-estradiol hair tonic improved the proportion of shedding hairs over at least 6 months; no new hair growth was seen. In a randomized comparison with minoxidil in 103 women, hair density and hair thickness increased markedly under minoxidil after 6 months, while under alfatradiol they remained almost unchanged. The authors interpret this as a slowing or stabilization of hair loss (Blume-Peytavi 2007). More on this on the page on minoxidil.
Where the data stop
- Life extension in humans. There is not a single study in which humans took 17α-estradiol. All lifespan data come from mice.
- A benefit for women. Female mice did not live longer in any of the ITP studies. Why the effect depends on sex is unresolved.
- Safety when taken orally. On breast, prostate, blood clotting, fertility or liver under orally taken 17α-estradiol, there are no data in humans, only a short tolerability study in marmosets.
- Hair growth. On the scalp, the solution tends to stabilize hair loss rather than make new hair grow; in a direct comparison, minoxidil was more effective.
Status, approval and legal
In Germany, alfatradiol is in principle prescription-only under the Ordinance on Prescription-Only Medicines (Arzneimittelverschreibungsverordnung). The exception is use on the scalp in mild androgenetic alopecia in people aged 18 and over: for this it is approved as a solution and available in pharmacies without a prescription.
There is no medicine to be taken by mouth, nor any approval or human study for life extension. Any systemic use for this purpose is an experiment without a data basis in humans; doses from animal experiments cannot be transferred.
Safety
For the solution on the scalp, no side effects were observed in the two studies, or both preparations were described as well tolerated.
For oral intake, safety data in humans are missing entirely. 17α-estradiol is an estrogen isomer; even though it had hardly any feminizing effect in mice and marmosets, hormonal effects in humans are not ruled out and have not been studied. In mice, body weight also fell markedly.
BK-Score Hype far ahead of evidence
| Human evidence | 2 | |
|---|---|---|
| Mechanism | 5 | |
| Safety data | 3 | |
| Hype gap | 2 | |
| Track record of use | 4 |
Evidence 2, because life extension has been shown only in male mice – in three studies of the Interventions Testing Program, most recently by 19 percent when started at 16 months of age (Harrison 2021) – and in humans there are only two small studies on use on the scalp. Mechanism 5, because the metabolic effects in mice run largely via estrogen receptor alpha, but it remains open why only males benefit. Safety 3, because the scalp solution has been used for decades without notable side effects, but there are no safety data at all for oral intake in humans, only a short pilot study in marmosets. Hype 2, because 17α-estradiol is considered in the longevity scene to be one of the strongest agents from the mouse program, without a single human study on oral intake existing. Use 4, because the scalp solution has long been on the market in Germany, but oral intake in humans is not documented. Direction open: in humans there are no data for the advertised effect.
The score rates the state of knowledge, not the substance. “Safety data 9” means well studied – not harmless. “Track record of use 9” means used long and widely – that is not proof of efficacy.
Subjective assessment by Biohacking Kompakt based on published scoring rules – not a scientific rating and not a medical recommendation. Rules and all ratings (German)
Frequently asked questions about 17α-estradiol (alfatradiol)
Does 17α-estradiol extend life?
In male mice, yes, in three studies of the US lifespan program ITP, most recently by 19 percent when started at 16 months of age. Female mice did not live longer. In humans, there is not a single study on this.
Why does 17α-estradiol work only in male mice?
That is unresolved. It is known that many metabolic effects run via estrogen receptor alpha, among other places in the hypothalamus. Why females do not benefit is currently being investigated.
Is 17α-estradiol the same as alfatradiol?
Yes. Alfatradiol is the drug name of 17α-estradiol. In Germany it is available without a prescription in pharmacies as a solution for use on the scalp in mild hereditary hair loss from age 18.
Does alfatradiol help against hair loss?
It can slow hair loss. In a double-blind study with 51 patients, the proportion of shedding hairs fell more often than under control; no new hair grew. In a direct comparison with minoxidil in 103 women, hair density and hair thickness increased only under minoxidil.
Can 17α-estradiol be taken as a longevity agent?
For this there is neither an approved medicine nor a study in humans. All data on life extension come from mice; on safety when taken orally there are no data in humans. Such use would be an experiment without a data basis.
Related
- Related topicAcarbose
- Related topicMinoxidil
- Related topicCanagliflozin (SGLT2 inhibitor)
- Related topicKetoconazole shampoo against hair loss
- Related topicClascoterone (Winlevi / Breezula)
- Related topicDutasteride
Sources
- Harrison DE et al., Aging Cell 2014 – ITP: acarbose, 17-α-estradiol and NDGA extend life mainly in male mice
- Strong R et al., Aging Cell 2016 – ITP: triple dose of 17-α-estradiol extends median and maximum lifespan of male mice
- Harrison DE et al., Aging Cell 2021 – ITP: 17-α-estradiol extends life in male mice even when started at 16 and 20 months
- Santín-Márquez R et al., Ageing Res Rev 2026 – review: 17α-estradiol, sex-specific effects on metabolism and lifespan, role of ERα
- Camon C et al., GeroScience 2024 – metabolic effects of 17α-estradiol do not depend solely on ERα in specific neurons (mouse)
- Sathiaseelan R et al., GeroScience 2025 – pilot study on the tolerability of 17α-estradiol in male marmosets
- Orfanos CE and Vogels L, Dermatologica 1980 – 17α-estradiol hair tonic in androgenetic alopecia, controlled double-blind study with 51 patients
- Blume-Peytavi U et al., J Dtsch Dermatol Ges 2007 – minoxidil versus alfatradiol in female androgenetic alopecia, randomized, 103 women
- Hoffmann R et al., Exp Dermatol 2002 – 17α-estradiol increases aromatase activity in human hair follicles ex vivo
- German Ordinance on Prescription-Only Medicines (AMVV), Annex 1 – alfatradiol prescription-only, except for use on the scalp in mild androgenetic alopecia from age 18
Open in the database – with search, filters and comparison (German app)
Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in the hands of a physician. Last updated: 2026-10-07.