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Title: Alfatradiol  
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Subject: Estrone sulfate, Lapisteride, Galeterone, Bexlosteride, Turosteride
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Skeletal formula of alfatradiol
Ball-and-stick model of the alfatradiol molecule
Systematic (IUPAC) name
Clinical data
  • US: C (Risk not ruled out)
  • No studies
Legal status
Routes of
CAS Registry Number  YesY
ATC code None
PubChem CID:
ChemSpider  YesY
Synonyms 17-Epiestradiol
Chemical data
Formula C18H24O2
Molecular mass 272.37 g/mol

Alfatradiol (INN,[1] or 17α-estradiol, trade names Ell-Cranell Alpha and Pantostin in Germany) is a 5α-reductase inhibitor used topically for the treatment of androgenic alopecia (hair loss) in men and women.[2]


Alfatradiol is used in form of an ethanolic solution for topical application on the scalp. Similarly to other drugs against alopecia, topical or oral, it has to be applied continuously to prevent further hair loss.[3] Regrowth of hair that was already lost is only possible to a limited extent. In general, advanced alopecia does not respond well to medical treatment, which has historically been thought to be a consequence of the hair roots being lost.[4]

A university-led study (including several authors who are advisors to companies such as Pfizer) in 103 women comparing alfatradiol to minoxidil, another topical hair loss treatment, found the latter to be more effective. In contrast to minoxidil, alfatradiol did not result in an increase of hair density or thickness, but only in slowing down or stabilization of hair loss in this study.[5] In an earlier study, no systemic side effects were noted, and 17α-estradiol was found to reduce androgenic hair loss, though it was not effective at growing new hair.[6]


Nothing is known about the use of alfatradiol during pregnancy or lactation, or in patients under 18 years of age. It should not be used under these circumstances.[7]

Adverse effects

Local burning or itching is not an effect of alfatradiol, but of the ethanol in the solvent. The solution can stimulate sebum production.[7]

Chemistry and pharmacology

Alfatradiol (top) and 17β-estradiol (bottom)

Alfatradiol (17α-estradiol) is distinguished from estradiol (17β-estradiol), the predominant sex hormone in females, only by the stereochemistry of the carbon atom 17. In contrast to 17β-estradiol, 17α-estradiol, while it still binds to the estrogen receptor, has less or no feminizing estrogen activity depending on its dosage and the tissue it is affecting.[8] Alfatradiol acts as an inhibitor of the enzyme 5α-reductase, which is responsible for the activation of testosterone to dihydrotestosterone, and which plays a role in regulating hair growth.[3] 17α-Estradiol has been studied as a therapeutic with potential to treat Alzheimer's and Parkinson's disease and other patients suffering from neurodegenerative diseases.[9] 17α-Estradiol (as the sodium salt of its sulfated form) is a minor component (<10%) of hormone replacement products (such as Premarin), which have been studied and/or marketed in women and men since the 1930s. A survey of the effects of various forms of 17α-estradiol in humans on biochemical parameters, efficacy, estrogenicity, metabolism, safety, and tolerability has been published.[10]

Alfatradiol has 100-fold lower estrogenic activity relative to estradiol.[11]

See also


  1. ^
  2. ^
  3. ^ a b
  4. ^
  5. ^
  6. ^ C.E. Orfanos, L. Vogels, Local therapy of androgenetic alopecia with 17α-estradiol. A controlled randomized double-blind study, Dermatologica 1980, 161:124-132.
  7. ^ a b
  8. ^ W.H. Moos, J.A. Dykens, N. Howell, 17α-Estradiol: A Less-Feminizing Estrogen, Drug Dev. Res. 2008, 69:177-184.
  9. ^ J.A. Dykens, W.H. Moos, N. Howell, Development of 17α-Estradiol as a Neuroprotective Therapeutic Agent. Rationale and Results from a Phase I Clinical Study, Ann. N. Y. Acad. Sci. 2005, 1052:116-135.
  10. ^ W.H. Moos, J.A. Dykens, D. Nohynek, E. Rubinchik, N. Howell, Review of the Effects of 17α-Estradiol in Humans: A Less Feminizing Estrogen with Neuroprotective Potential, Drug Dev. Res. 2009, 70:1-21.
  11. ^
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