Review of the Effects of 17α-Estradiol in Humans: A Less Feminizing Estrogen with Neuroprotective Potential

The document reviews the potential neuroprotective effects of 17α-estradiol, a less feminizing estrogen, in humans. It has been used in FDA-approved hormone replacement products for over 65 years and may have therapeutic potential for neurodegenerative diseases like Alzheimer's and Parkinson's. Despite its extensive use, there are no studies of it as a single agent for these diseases in humans. The review includes a Phase I clinical trial with eight postmenopausal women, showing dose-dependent pharmacokinetics and safety. A pilot study with six men over 50 showed no metabolism to more potent estrogens after 12 weeks of treatment. In vitro studies and a controlled trial on alopecia androgenetica indicated antioxidant potential and a reduction in telogen hairs without significant side effects. The document concludes that 17α-estradiol is well tolerated, does not metabolize to feminizing hormones, and has potential therapeutic value without adverse effects. Further testing in animal models and humans at non-feminizing doses is warranted.