--- title: "17-alpha-Estradiol: Research & Side Effects" url: https://www.bodyhackguide.co/compound/alpha-estradiol description: "17-alpha-Estradiol: mechanism, clinical studies & side effects." lang: en --- Skip to content Compare notes on r/BodyHackGuide (https://reddit.com/r/bodyhackguide) Compare notes with other researchers. Join r/BodyHackGuide (https://reddit.com/r/bodyhackguide) # 17-alpha-Estradiol Longevity: https://www.bodyhackguide.co/wiki#cat-longevity Status Phase 4 for topical use in hair loss (PMID: 17451383) Evidence Not graded on a research bench yet 17-alpha-estradiol (alfatradiol) is a naturally occurring steroid estrogen, the C17 epimer of the main estrogen 17beta-estradiol, that extends lifespan in male mice, where it causes only mild feminizing effects. Reviewed 4 November 2026 01 Overview ## What 17-alpha-Estradiol is In the US National Institute on Aging's Interventions Testing Program, 17-alpha-estradiol in the diet extended the median lifespan of male mice by 11 to 19 percent in four treatment groups, among them starts at 16 and 20 months of age, but did not extend female lifespan in the two tests that included females (PMID: 24245565, PMID: 27312235, PMID: 33788371). Separately, alfatradiol is authorised for cutaneous use in Germany, where a 2007 trial report described it as approved for androgenetic alopecia in women, and small controlled trials found fewer resting-phase hairs or stabilization of hair loss rather than regrowth (EMA Article 57 list of authorised medicines, file dated 13 October 2026; PMID: 17451383, PMID: 7398983). No human trial has tested 17-alpha-estradiol for aging. ### How it works ### A stereoisomer of estradiol 17-alpha-estradiol differs from 17beta-estradiol only in the orientation of the hydroxyl group at carbon 17 (PMID: 42142594, PMID: 16024755). Using mass spectrometry, a Columbia University group led by C. Dominique Toran-Allerand measured endogenous 17-alpha-estradiol in the brain and adrenal glands of male and female mice, at higher levels than 17beta-estradiol in the neocortex and hippocampus, and also found it in the brains of mice whose gonads, or gonads and adrenal glands, had been removed (PMID: 15947006, PMID: 16024756). Read the full mechanism Show less ### Estrogen receptor activity: conflicting results In a 1997 Karolinska Institute study of human estrogen receptor alpha (ERalpha) and rat estrogen receptor beta (ERbeta) proteins, 17-alpha-estradiol competed for receptor binding less strongly than 17beta-estradiol at both receptor subtypes (PMID: 9048584). The Columbia group reported in 2005 that the two estradiols bound estrogen receptors with similar affinity, that 17-alpha-estradiol switched on an estrogen-responsive reporter gene, and that, unlike 17beta-estradiol, it did not bind the plasma proteins alpha-fetoprotein or sex hormone-binding globulin (SHBG) (PMID: 15947006). The same group described a membrane-associated estrogen-binding site in mouse brain, which it named ER-X, through which both estradiols activated the MAPK/ERK signaling pathway, and called 17-alpha-estradiol its preferred ligand (PMID: 12351713, PMID: 16024756). Authors from the drug developer MIGENIX described 17-alpha-estradiol as at least 200-fold less active than 17beta-estradiol as a transactivating hormone, but as potent as 17beta-estradiol in protecting cultured cells such as neurons from a range of lethal stressors (PMID: 16024755). In the Interventions Testing Program, the 14.4 ppm diet raised uterine weight in ovariectomized mice to the level of intact controls, which the investigators took as evidence that 17-alpha-estradiol acts on classical estrogen receptors at higher concentrations (PMID: 27312235). ### How 17-alpha-estradiol acts in male mice (animal data) Most of this work comes from Michael Stout's group, first at the Mayo Clinic and later in Oklahoma, and from Richard Miller's group at the University of Michigan, one of the three ITP test sites (PMID: 26809497, PMID: 33289482, PMID: 28834262, PMID: 24245565). - In old male mice, 17-alpha-estradiol lowered food intake, body mass, visceral fat and fat stored in other organs without reducing lean mass; lowered fasting glucose, insulin and HbA1c; improved glucose disposal in clamp studies; reduced inflammatory markers; and raised AMPK and lowered mTORC1 activity in visceral fat, without feminization or cardiac dysfunction (PMID: 26809497). In mouse models of obesity, the fall in food intake depended on pro-opiomelanocortin (Pomc) expression in the arcuate nucleus of the hypothalamus, an appetite-control center (PMID: 29168299). - 17-alpha-estradiol produced genomic binding and gene activation through ERalpha similar to 17beta-estradiol, its metabolic benefits disappeared in male mice lacking ERalpha, and it also improved metabolic measures in male rats (PMID: 33289482). - A mouse study tested the role of male hormones: male mice given 17-alpha-estradiol, but not females, gained insulin sensitivity, glucose tolerance and liver mTORC2 signaling; castrated males showed fewer of these responses, and ovariectomized females showed some of them (PMID: 28834262). 17-alpha-estradiol also reduced age-related hypothalamic inflammation in male mice at 12 months of age, not in females (PMID: 28544365). ### Hair follicles (laboratory data) In hair follicles from female donors studied outside the body, 17-alpha-estradiol raised aromatase activity in a concentration- and time-dependent way, which the Marburg authors proposed would shift testosterone toward 17beta-estradiol and androstenedione toward estrone (PMID: 12190948). A Berlin study in cultured human skin cells concluded that the effects of 17-alpha-estradiol in androgenetic alopecia are not due to inhibition of 5-alpha-reductase (PMID: 14528059). ### Studied for - Aging biology - Sex differences in aging - Endocrinology - Metabolism - Dermatology - Neuroendocrinology ### Benefits listed - Median lifespan of male mice, 19 percent longer at 14.4 ppm in the diet from 10 months of age (PMID: 27312235) - Male mouse lifespan when started at 16 or 20 months of age, 19 and 11 percent longer (PMID: 33788371) - Fasting glucose, visceral fat, insulin and inflammation markers in old male mice (PMID: 26809497) - Muscle mass, grip strength and rotarod performance in aging male mice (PMID: 30740872) Show 3 more Show less - Weight gain and bone loss after ovary removal in young female mice (PMID: 33065227) - Share of resting-phase (telogen) hairs in a 1980 double-blind trial of a scalp lotion in 51 patients (PMID: 7398983) - Hair counts and hair diameter in an uncontrolled 8-month study of 53 Korean women (PMID: 22879713) 02 Research Free with email ## What the research shows No research bench grades 17-alpha-Estradiol yet. Benches compare compounds people pair, with the evidence for each. ### Unlock the research summary Enter your email to keep reading. It is free, and it opens these sections on every compound page in this browser. - A summary of the key research - Safety and side effects - A link to the PubMed results You also get the free peptide cheat sheet by email. Unsubscribe anytime. Have an account? Sign in (https://www.bodyhackguide.co/auth) 03 Safety ## 17-alpha-Estradiol side effects and interactions ### Side effects #### Common - No side effects seen in a 1980 double-blind trial of a 17-alpha-estradiol scalp lotion in 51 patients (PMID: 7398983) - Good tolerability of a 0.025 percent scalp solution in a randomized trial in 103 women and an 8-month open study in 53 women (PMID: 17451383, PMID: 22879713) - Body weight about 20 percent lower in male mice after late-start treatment (PMID: 33788371) #### Serious events - Testicular atrophy, higher estrogens and suppressed androgens and gonadotropins in male rhesus macaques (PMID: 36897526) - Uterine growth in ovariectomized mice at the higher dose used in ITP studies (PMID: 27312235) - Fewer primordial ovarian follicles in long-lived growth hormone receptor knockout female mice (PMID: 31698046) ### Who should not use it Contraindications In mice, 17-alpha-estradiol acts through estrogen receptor alpha and, at the higher ITP dose, stimulated uterine growth in ovariectomized animals, so estrogen-sensitive conditions are a mechanism-based reason for caution (PMID: 33289482, PMID: 27312235). For men, the caution comes from male rhesus macaques, in which 17-alpha-estradiol caused testicular atrophy and lower androgen and gonadotropin levels (PMID: 36897526). No human data were found for pregnancy or breastfeeding. 17-alpha-estradiol is not the estradiol used in hormone therapy: it is a different molecule from 17beta-estradiol, the main estrogen, with weaker feminizing effects in male mice (PMID: 42142594). For aging use, the lifespan and metabolic results come from mice and rats, and no human trial has tested 17-alpha-estradiol for aging. ### Interactions Not in our record Our record lists no interactions for 17-alpha-Estradiol. That means none are recorded here, not that none exist. This interaction data is compiled from published research and community reports. It may not be exhaustive. Always consult a healthcare professional before combining compounds. Need bloodwork before starting? Full hormone + metabolic panels from Anabolic Insights. Code CHONCH for first-order discount. Order Bloodwork (https://anabolicinsights.ai/?ref=nwm2zjb) 04 Dosing Free with email ## Dosing No dose on record Our record lists no dose for 17-alpha-Estradiol. This section holds what it does list. ### Unlock the Dosing section - Route 05 Prices ## 17-alpha-Estradiol prices No listings We do not track a vendor for 17-alpha-Estradiol yet, so this page states no price. 06 Chemistry ## Chemistry and structure Molecular formula C18H24O2 Molecular mass 272.4 g/mol CAS number 57-91-0 Half-life No published human half-life value was found. In male volunteers given 17-alpha-estradiol by mouth, the drug was rapidly and heavily conjugated and less than 1 percent of the 17-alpha-estradiol in serum was in the free form, while taken under the tongue it gave higher free levels for up to 3 hours (PMID: 12234624). View on PubChem (https://pubchem.ncbi.nlm.nih.gov/compound/68570) 07 Related ## Related to 17-alpha-Estradiol ### In the same category - AcarbosePhase 4 Acarbose is a prescription alpha-glucosidase inhibitor for type 2 diabetes, a complex oligosaccharide produced by fermentation of the bacterium Actinoplanes utahensis, that slows the digestion of starch and table sugar in the small intestine (US prescribing information for Precose).: https://www.bodyhackguide.co/compound/acarbose - Alpha-Ketoglutarate (AKG)Phase 2 Alpha-ketoglutarate (AKG, also called 2-oxoglutarate) is an intermediate of the tricarboxylic acid (Krebs) cycle that cells make from isocitrate and from glutamate, and its calcium salt (Ca-AKG) is the form used in the main aging studies in mice and people.: https://www.bodyhackguide.co/compound/alpha-ketoglutarate-akg - CanagliflozinPhase 4 Canagliflozin is a sodium-glucose cotransporter 2 (SGLT2) inhibitor, a C-glucoside discovered by chemists at Mitsubishi Tanabe Pharma, that lowers blood glucose in type 2 diabetes by making the kidneys excrete glucose in the urine; the FDA approved canagliflozin in 2013 as Invokana.: https://www.bodyhackguide.co/compound/canagliflozin - CMS121Phase 1 CMS121 is a synthetic derivative of the flavonol fisetin, made at the Salk Institute for Biological Studies in La Jolla in the Cellular Neurobiology Laboratory of Pamela Maher and David Schubert, as part of a series of more than 160 fisetin derivatives.: https://www.bodyhackguide.co/compound/cms-121 - CortagenPreclinical Cortagen is a synthetic tetrapeptide, Ala-Glu-Asp-Pro (AEDP), made at Vladimir Khavinson's St. Petersburg Institute of Bioregulation and Gerontology from the amino acid analysis of Cortexin, a peptide preparation from the brain cortex.: https://www.bodyhackguide.co/compound/cortagen - NAD+Phase 2 NAD+ (nicotinamide adenine dinucleotide, oxidized form) is a pyridine dinucleotide coenzyme essential to energy metabolism, DNA repair via PARP enzymes, sirtuin-mediated gene regulation, and calcium signaling via CD38.: https://www.bodyhackguide.co/compound/nad All compounds (https://www.bodyhackguide.co/wiki) ### Compare 17-alpha-Estradiol - Alternatives to 17-alpha-Estradiol: https://www.bodyhackguide.co/alternatives-to/alpha-estradiol ### Research tools - Peptide Calculator Reconstitution and syringe units: https://www.bodyhackguide.co/tools/reconstitution - Reconstitution Guide How to mix, step by step: https://www.bodyhackguide.co/guides/how-to-reconstitute-peptides - Nasal Spray Calc mL per actuation: https://www.bodyhackguide.co/tools/intranasal - Half-Life Visualizer Decay curves: https://www.bodyhackguide.co/tools/halflife All articles (https://www.bodyhackguide.co/blog) 08 Questions ## Frequently asked questions What is 17-alpha-estradiol? 17-alpha-estradiol is a steroid estrogen that differs from 17beta-estradiol, the main estrogen, only in the orientation of the hydroxyl group at carbon 17 (PMID: 42142594, PMID: 16024755). 17-alpha-estradiol occurs naturally in mice, where a Columbia University group measured it in the brain and adrenal glands of both sexes (PMID: 15947006). Under its drug name alfatradiol, 17-alpha-estradiol is authorised in Germany for cutaneous use (EMA Article 57 list of authorised medicines, file dated 13 October 2026). Does 17-alpha-estradiol extend lifespan? 17-alpha-estradiol at 14.4 ppm in the diet from 10 months of age extended the median lifespan of male mice by 19 percent in the NIA Interventions Testing Program, with no effect in female mice (PMID: 27312235). 17-alpha-estradiol still extended male mouse lifespan by 19 and 11 percent when started at 16 and 20 months of age (PMID: 33788371). No human study has tested whether 17-alpha-estradiol affects lifespan or aging. Why does 17-alpha-estradiol help only male mice? According to the ITP investigators, the reason 17-alpha-estradiol extends lifespan only in male mice is not known (PMID: 27312235). 17-alpha-estradiol improved insulin sensitivity and glucose tolerance in male mice but not in female mice, and castrated male mice showed fewer of these 17-alpha-estradiol responses (PMID: 28834262). 17-alpha-estradiol preserved muscle and grip strength in aging male mice but not in females or castrated males (PMID: 30740872). Is 17-alpha-estradiol feminizing? In a 2017 study, 17-alpha-estradiol caused no feminization or cardiac dysfunction in old male mice, and long-term 17-alpha-estradiol did not impair sperm quality or fertility in male mice (PMID: 26809497, PMID: 35689785). At the higher dose used in later ITP studies, 17-alpha-estradiol raised uterine weight in ovariectomized female mice (PMID: 27312235). In male rhesus macaques, 17-alpha-estradiol caused feminization such as testicular atrophy and suppressed androgens, while a short marmoset pilot study of 17-alpha-estradiol found no feminization (PMID: 36897526, PMID: 39107620). Is 17-alpha-estradiol used for hair loss? 17-alpha-estradiol is authorised for cutaneous use in Germany (EMA Article 57 list of authorised medicines, file dated 13 October 2026), and a 2007 trial report from Berlin described topical alfatradiol as one of two drugs approved in Germany for androgenetic alopecia in women (PMID: 17451383). In that randomized trial of 103 women, topical alfatradiol left hair density and thickness nearly unchanged over 6 months while topical minoxidil increased them, and the authors concluded that alfatradiol slows or stabilizes hair loss (PMID: 17451383). In a 1980 double-blind trial, a 17-alpha-estradiol lotion reduced the share of resting-phase hairs but produced no regrowth of new hair (PMID: 7398983). What is the regulatory status of 17-alpha-estradiol? 17-alpha-estradiol is not an FDA-approved drug, and a search of Drugs@FDA through openFDA on 27 October 2026 found no product containing alfatradiol. 17-alpha-estradiol, as alfatradiol, is authorised for cutaneous use in Germany under the names Ell-Cranell and Pantostin (EMA Article 57 list of authorised medicines, file dated 13 October 2026). No approval was found for 17-alpha-estradiol taken by mouth or for aging. Has 17-alpha-estradiol been tested in people for aging? No human trial of 17-alpha-estradiol for aging was found in PubMed or ClinicalTrials.gov on 27 October 2026. The human data on 17-alpha-estradiol come from small topical hair-loss trials, a metabolism study in male volunteers and a phase 1 study of an oral form reported by its developer (PMID: 17451383, PMID: 12234624, PMID: 16024755). Researchers studying 17-alpha-estradiol for aging have tested its tolerability in rhesus macaques and marmosets as a step toward human studies (PMID: 36897526, PMID: 39107620). Free 2026 Peptide Cheat Sheet (PDF) 38 compounds and blends: vial sizes, BAC water volumes, dosing ranges and bloodwork markers. Download Free (https://www.bodyhackguide.co/guides/peptide-cheat-sheet-download) BodyHackGuide (https://www.bodyhackguide.co/) Your biohacking research hub: compound pricing, brain health protocols, dosing tools, and vendor reviews. support@bodyhackguide.co Join our Discord: https://discord.gg/Mhq5UdRYBA r/BodyHackGuide on Reddit: https://reddit.com/r/BodyHackGuide **Affiliate Disclosure:** We rank every vendor on the same public, reproducible methodology (https://www.bodyhackguide.co/vendors/methodology). 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All rights reserved. - Terms: https://www.bodyhackguide.co/terms - Privacy: https://www.bodyhackguide.co/privacy ## Structured data ```json [ { "@context": "https://schema.org", "@type": "BreadcrumbList", "itemListElement": [ { "@type": "ListItem", "position": 1, "name": "Home", "item": "https://www.bodyhackguide.co/" }, { "@type": "ListItem", "position": 2, "name": "Compounds", "item": "https://www.bodyhackguide.co/compare" }, { "@type": "ListItem", "position": 3, "name": "17-alpha-Estradiol" } ] }, { "@context": "https://schema.org", "@type": "MedicalWebPage", "name": "17-alpha-Estradiol", "description": "17-alpha-estradiol (alfatradiol) is a naturally occurring steroid estrogen, the C17 epimer of the main estrogen 17beta-estradiol, that extends lifespan in male mice, where it causes only mild feminizing effects (PMID: 42142594, PMID: 15947006). In the US National Institute on Aging's Interventions Testing Program, 17-alpha-estradiol in the diet extended the median lifespan of male mice by 11 to 19 percent in four treatment groups, among them starts at 16 and 20 months of age, but did not extend female lifespan in the two tests that included females (PMID: 24245565, PMID: 27312235, PMID: 33788371). Separately, alfatradiol is authorised for cutaneous use in Germany, where a 2007 trial report described it as approved for androgenetic alopecia in women, and small controlled trials found fewer resting-phase hairs or stabilization of hair loss rather than regrowth (EMA Article 57 list of authorised medicines, file dated 13 October 2026; PMID: 17451383, PMID: 7398983). 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In the US National Institute on Aging's Interventions Testing Program, 17-alpha-estradiol in the diet extended the median lifespan of male mice by 11 to 19 percent in four treatment groups, among them starts at 16 and 20 months of age, but did not extend female lifespan in the two tests that included females (PMID: 24245565, PMID: 27312235, PMID: 33788371). Separately, alfatradiol is authorised for cutaneous use in Germany, where a 2007 trial report described it as approved for androgenetic alopecia in women, and small controlled trials found fewer resting-phase hairs or stabilization of hair loss rather than regrowth (EMA Article 57 list of authorised medicines, file dated 13 October 2026; PMID: 17451383, PMID: 7398983). No human trial has tested 17-alpha-estradiol for aging.", "activeIngredient": "17-alpha-Estradiol", "administrationRoute": "Topical, Oral, Sublingual", "mechanismOfAction": "A stereoisomer of estradiol 17-alpha-estradiol differs from 17beta-estradiol only in the orientation of the hydroxyl group at carbon 17 (PMID: 42142594, PMID: 16024755). Using mass spectrometry, a Columbia University group led by C. Dominique Toran-Allerand measured endogenous 17-alpha-estradiol in the brain and adrenal glands of male and female mice, at higher levels than 17beta-estradiol in the neocortex and hippocampus, and also found it in the brains of mice whose gonads, or gonads and adrenal glands, had been removed (PMID: 15947006, PMID: 16024756). Estrogen receptor activity: conflicting results In a 1997 Karolinska Institute study of human estrogen receptor alpha (ERalpha) and rat estrogen receptor beta (ERbeta) proteins, 17-alpha-estradiol competed for receptor binding less strongly than 17beta-estradiol at both receptor subtypes (PMID: 9048584). The Columbia group reported in 2005 that the two estradiols bound estrogen receptors with similar affinity, that 17-alpha-estradiol switched on an estrogen-responsive reporter gene, and that, unlike 17beta-estradiol, it did not bind the plasma proteins alpha-fetoprotein or sex hormone-binding globulin (SHBG) (PMID: 15947006). The same group described a membrane-associated estrogen-binding site in mouse brain, which it named ER-X, through which both estradiols activated the MAPK/ERK signaling pathway, and called 17-alpha-estradiol its preferred ligand (PMID: 12351713, PMID: 16024756). Authors from the drug developer MIGENIX described 17-alpha-estradiol as at least 200-fold less active than 17beta-estradiol as a transactivating hormone, but as potent as 17beta-estradiol in protecting cultured cells such as neurons from a range of lethal stressors (PMID: 16024755). In the Interventions Testing Program, the 14.4 ppm diet raised uterine weight in ovariectomized mice to the level of intact controls, which the investigators took as evidence that 17-alpha-estradiol acts on classical estrogen receptors at higher concentrations (PMID: 27312235). How 17-alpha-estradiol acts in male mice (animal data) Most of this work comes from Michael Stout's group, first at the Mayo Clinic and later in Oklahoma, and from Richard Miller's group at the University of Michigan, one of the three ITP test sites (PMID: 26809497, PMID: 33289482, PMID: 28834262, PMID: 24245565). In old male mice, 17-alpha-estradiol lowered food intake, body mass, visceral fat and fat stored in other organs without reducing lean mass; lowered fasting glucose, insulin and HbA1c; improved glucose disposal in clamp studies; reduced inflammatory markers; and raised AMPK and lowered mTORC1 activity in visceral fat, without feminization or cardiac dysfunction (PMID: 26809497). In mouse models of obesity, the fall in food intake depended on pro-opiomelanocortin (Pomc) expression in the arcuate nucleus of the hypothalamus, an appetite-control center (PMID: 29168299). 17-alpha-estradiol produced genomic binding and gene activation through ERalpha similar to 17beta-estradiol, its metabolic benefits disappeared in male mice lacking ERalpha, and it also improved metabolic measures in male rats (PMID: 33289482). A mouse study tested the role of male hormones: male mice given 17-alpha-estradiol, but not females, gained insulin sensitivity, glucose tolerance and liver mTORC2 signaling; castrated males showed fewer of these responses, and ovariectomized females showed some of them (PMID: 28834262). 17-alpha-estradiol also reduced age-related hypothalamic inflammation in male mice at 12 months of age, not in females (PMID: 28544365). Hair follicles (laboratory data) In hair follicles from female donors studied outside the body, 17-alpha-estradiol raised aromatase activity in a concentration- and time-dependent way, which the Marburg authors proposed would shift testosterone toward 17beta-estradiol and androstenedione toward estrone (PMID: 12190948). A Berlin study in cultured human skin cells concluded that the effects of 17-alpha-estradiol in androgenetic alopecia are not due to inhibition of 5-alpha-reductase (PMID: 14528059).", "legalStatus": "Not approved for human use (research chemical)", "warning": "For research purposes only. Not for human consumption." } }, { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "What is 17-alpha-estradiol?", "acceptedAnswer": { "@type": "Answer", "text": "17-alpha-estradiol is a steroid estrogen that differs from 17beta-estradiol, the main estrogen, only in the orientation of the hydroxyl group at carbon 17 (PMID: 42142594, PMID: 16024755). 17-alpha-estradiol occurs naturally in mice, where a Columbia University group measured it in the brain and adrenal glands of both sexes (PMID: 15947006). Under its drug name alfatradiol, 17-alpha-estradiol is authorised in Germany for cutaneous use (EMA Article 57 list of authorised medicines, file dated 13 October 2026)." } }, { "@type": "Question", "name": "Does 17-alpha-estradiol extend lifespan?", "acceptedAnswer": { "@type": "Answer", "text": "17-alpha-estradiol at 14.4 ppm in the diet from 10 months of age extended the median lifespan of male mice by 19 percent in the NIA Interventions Testing Program, with no effect in female mice (PMID: 27312235). 17-alpha-estradiol still extended male mouse lifespan by 19 and 11 percent when started at 16 and 20 months of age (PMID: 33788371). No human study has tested whether 17-alpha-estradiol affects lifespan or aging." } }, { "@type": "Question", "name": "Why does 17-alpha-estradiol help only male mice?", "acceptedAnswer": { "@type": "Answer", "text": "According to the ITP investigators, the reason 17-alpha-estradiol extends lifespan only in male mice is not known (PMID: 27312235). 17-alpha-estradiol improved insulin sensitivity and glucose tolerance in male mice but not in female mice, and castrated male mice showed fewer of these 17-alpha-estradiol responses (PMID: 28834262). 17-alpha-estradiol preserved muscle and grip strength in aging male mice but not in females or castrated males (PMID: 30740872)." } }, { "@type": "Question", "name": "Is 17-alpha-estradiol feminizing?", "acceptedAnswer": { "@type": "Answer", "text": "In a 2017 study, 17-alpha-estradiol caused no feminization or cardiac dysfunction in old male mice, and long-term 17-alpha-estradiol did not impair sperm quality or fertility in male mice (PMID: 26809497, PMID: 35689785). At the higher dose used in later ITP studies, 17-alpha-estradiol raised uterine weight in ovariectomized female mice (PMID: 27312235). In male rhesus macaques, 17-alpha-estradiol caused feminization such as testicular atrophy and suppressed androgens, while a short marmoset pilot study of 17-alpha-estradiol found no feminization (PMID: 36897526, PMID: 39107620)." } }, { "@type": "Question", "name": "Is 17-alpha-estradiol used for hair loss?", "acceptedAnswer": { "@type": "Answer", "text": "17-alpha-estradiol is authorised for cutaneous use in Germany (EMA Article 57 list of authorised medicines, file dated 13 October 2026), and a 2007 trial report from Berlin described topical alfatradiol as one of two drugs approved in Germany for androgenetic alopecia in women (PMID: 17451383). In that randomized trial of 103 women, topical alfatradiol left hair density and thickness nearly unchanged over 6 months while topical minoxidil increased them, and the authors concluded that alfatradiol slows or stabilizes hair loss (PMID: 17451383). In a 1980 double-blind trial, a 17-alpha-estradiol lotion reduced the share of resting-phase hairs but produced no regrowth of new hair (PMID: 7398983)." } }, { "@type": "Question", "name": "What is the regulatory status of 17-alpha-estradiol?", "acceptedAnswer": { "@type": "Answer", "text": "17-alpha-estradiol is not an FDA-approved drug, and a search of Drugs@FDA through openFDA on 27 October 2026 found no product containing alfatradiol. 17-alpha-estradiol, as alfatradiol, is authorised for cutaneous use in Germany under the names Ell-Cranell and Pantostin (EMA Article 57 list of authorised medicines, file dated 13 October 2026). No approval was found for 17-alpha-estradiol taken by mouth or for aging." } }, { "@type": "Question", "name": "Has 17-alpha-estradiol been tested in people for aging?", "acceptedAnswer": { "@type": "Answer", "text": "No human trial of 17-alpha-estradiol for aging was found in PubMed or ClinicalTrials.gov on 27 October 2026. The human data on 17-alpha-estradiol come from small topical hair-loss trials, a metabolism study in male volunteers and a phase 1 study of an oral form reported by its developer (PMID: 17451383, PMID: 12234624, PMID: 16024755). Researchers studying 17-alpha-estradiol for aging have tested its tolerability in rhesus macaques and marmosets as a step toward human studies (PMID: 36897526, PMID: 39107620)." } } ] }, { "@context": "https://schema.org", "@type": "Organization", "@id": "https://www.bodyhackguide.co#organization", "name": "BodyHackGuide", "alternateName": "BHG", "url": "https://www.bodyhackguide.co", "logo": { "@type": "ImageObject", "url": "https://www.bodyhackguide.co/logo.png", "width": 512, "height": 512 }, "description": "Evidence-based research reference for peptides and nootropics. 273 compound profiles, interactive dosing calculators, vendor price comparisons, and trust-scored vendor reviews scored on a public, reproducible methodology applied to every vendor. 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