17α-Estradiol

17α-Estradiol is a stereoisomer of the dominant estrogen 17β-estradiol with much weaker feminizing activity. In the NIA Interventions Testing Program, it consistently extended median lifespan in male mice, possibly via hypothalamic and metabolic effects. Mechanism is incompletely understood and human longevity data do not exist; it is not approved or established as a human anti-aging therapy.