5-androstene-3alpha,17beta-diol

5-Androstene-3alpha,17beta-Diol

1. Identity, Nomenclature, and Chemical Character

5-Androstene-3alpha,17beta-diol is an endogenous androstane steroid belonging to the large family of androstenediol isomers derived, directly or indirectly, from the adrenal precursor dehydroepiandrosterone (DHEA). Its systematic IUPAC name is (3alpha,17beta)-androst-5-ene-3,17-diol, and it shares the molecular formula C₁₉H₃₂O₂ (molecular weight 292.46 g/mol) with all other androstenediol positional and stereo-isomers.

The compound is best understood within the context of its broader isomeric family. Androstenediol — most commonly encountered as androst-5-ene-3beta,17beta-diol (abbreviated A5 or Δ5-diol) — is an endogenous weak androgen and estrogen steroid hormone and an intermediate in the biosynthesis of testosterone from DHEA. The 3alpha,17beta form differs from this well-characterised 3beta,17beta form solely in the axial orientation of the C-3 hydroxyl group: the alpha configuration places the C-3 hydroxyl in an axial (below-the-plane) position on the A ring, whereas the beta form carries it in the equatorial position. This single stereochemical difference produces distinct receptor-binding profiles and metabolic fates.

Androstenediol is a naturally occurring androstane steroid closely related structurally to androstenedione (A4; androst-4-ene-3,17-dione), dehydroepiandrosterone (DHEA; androst-5-en-3beta-ol-17-one), and testosterone (androst-4-en-17beta-ol-3-one), as well as to 3beta-androstanediol (5alpha-androstane-3beta,17beta-diol).

1.1 Nomenclature Disambiguation

The "androstenediol" family encompasses multiple distinct stereoisomers that are frequently conflated in the supplement and even the older scientific literature. The four principal naturally occurring variants sharing the Δ5 double bond are:

• Androst-5-ene-3beta,17beta-diol (5-AED; the 3β-form): the most extensively studied, also the primary subject of radiation countermeasure research and the depot-formulation drug candidate NEUMUNE.
• Androst-5-ene-3alpha,17beta-diol (the 3α-form, the subject of this article): the epimer with an axial C-3 hydroxyl; less studied as an isolated entity.
• Androst-5-ene-3beta,17alpha-diol: the 17α-epimer of the common form.
• Androst-5-ene-3alpha,17alpha-diol: the double-alpha epimer, of primarily synthetic interest.

Additionally, saturated androstane analogs exist, including 3alpha-androstanediol (also known as 5alpha-androstane-3alpha,17beta-diol), a naturally occurring androstane steroid and structural analogue of DHT (5alpha-androstan-17beta-ol-3-one). This saturated 5alpha-androstane analog is biochemically related but structurally distinct from the 5-ene (Δ5 double bond-containing) compound discussed here.

In dietary supplement contexts, 5-androstene-3alpha,17beta-diol has been marketed as a "prohormone" alongside the 3beta counterpart, sometimes under the general label "androstenediol," and has appeared in multi-compound stacks. The broad scientific literature — including all radiation countermeasure work, immunomodulatory studies, and most receptor-binding studies — has predominantly characterised the 3beta,17beta-diol isomer; data specifically isolated to the 3alpha,17beta-diol form are notably limited. This article draws upon data from both isomers where directly applicable, with distinctions explicitly noted.

1.2 Natural Sources and Endogenous Occurrence

Androstenediol is a direct metabolite of the most abundant steroid produced by the human adrenal cortex, DHEA. From five to seven percent of DHEA in both men and women is converted into androstenes, particularly Δ5-androstenediol (5-AED). The compound is thus an endogenous, physiologically present steroid rather than a plant- or fungal-derived exogenous substance. It is not concentrated in any particular botanical source; its primary "natural source" is the human (and mammalian) adrenal cortex and gonads via enzymatic interconversion of DHEA.

5alpha-androstanediol isomers are naturally occurring compounds that have been identified as direct metabolites of dihydrotestosterone in placental, uterine, testicular, adrenal and nervous system tissues. The 5-ene (Δ5) variant of the 3alpha,17beta-diol specifically arises from the same DHEA → androstenediol metabolic axis that produces the better-characterised 3beta form, with the alpha versus beta orientation at C-3 determined by the specific 3-hydroxysteroid dehydrogenase (3-HSD) isoform acting on the C-3 ketone or hydroxyl.

1.3 Common Preparations and Supplement Forms

In the dietary supplement market, androstenediol isomers have been sold in the following forms:

• Oral capsules and tablets — the most prevalent consumer supplement form, used as prohormone preparations.
• Sublingual (under-the-tongue) tablets or liquids — employed in an attempt to bypass first-pass hepatic metabolism and improve bioavailability.
• Transdermal creams and gels — applied to the skin to achieve direct systemic absorption.
• Injectable depot formulations (investigational) — the injectable aqueous suspension formulation designated NEUMUNE was developed specifically for the 3beta,17beta-diol isomer as a potential radiation countermeasure. The United States Food and Drug Administration granted investigational new drug (IND) status to its injectable depot formulation.

Derivatives and analogues of androstenediol, such as the 17alpha-substituted methandriol (17alpha-methylandrostenediol) and ethinylandrostenediol (17alpha-ethynylandrostenediol), as well as the naturally occurring 19-norandrostane derivative norandrostenediol (19-nor-5-androstenediol), have been synthesized and studied.

2. Historical and Traditional Use

The androstenediol family does not have a documented history of use in classical herbal medicine traditions (such as Ayurveda, Traditional Chinese Medicine, or European phytotherapy), because the compound was not isolatable or identifiable as a discrete chemical entity prior to modern steroid chemistry. Its existence as an endogenous steroid was characterised in the mid-twentieth century alongside broader advances in steroid biochemistry.

Since 1954, androst-5-ene-3beta,17beta-diol (Adiol) has been known to have estrogenic activity at physiological concentrations. Early biochemical interest centred on its role in the DHEA → testosterone biosynthetic axis. The immunomodulatory potential of these DHEA-derived steroids was recognised progressively through the 1980s and 1990s, primarily through the work of researchers studying DHEA's ability to counteract glucocorticoid-mediated immunosuppression.

The estrogenic effect of Adiol, mediated by the estrogen receptor (ER), has been proposed as an essential female hormone that can partially replace the loss of 17beta-estradiol (E2) for postmenopausal women. This observation prompted interest in its therapeutic utility in the context of menopause and age-related hormonal decline.

Androstenediol — including the 3alpha isomer sold alongside the 3beta form — entered the bodybuilding and performance-enhancement supplement market in the late 1990s in the wake of publicity around DHEA and androstenedione. It was marketed as a "prohormone" capable of raising testosterone levels. This commercial use was not rooted in traditional medicine but rather in the application of steroid biochemistry to athletic enhancement. In October 2004, President George Bush signed the Anabolic Steroid Control Act, which reclassified androstenedione from a supplement to an anabolic steroid, making it and other steroid-based drugs a controlled substance. The regulatory environment for the broader androstenediol class changed correspondingly in a number of jurisdictions.

3. Key Constituents and Active Compounds

As a single discrete steroid molecule rather than a botanical extract, 5-androstene-3alpha,17beta-diol does not contain "constituent compounds" in the phytochemical sense. Its biological activity is intrinsic to its molecular structure. However, because it is both a metabolic precursor and a metabolite within a cascade, its pharmacological profile is intertwined with the activity of related steroids it can be interconverted with.

3.1 Structural Features Determining Activity

The molecule possesses two hydroxyl groups — at C-3 and C-17 — and a Δ5 double bond between C-5 and C-6. The beta orientation at C-17 (17beta-OH) is essential for meaningful androgen receptor (AR) binding, as the 17beta-hydroxyl configuration is conserved across nearly all AR-binding androgens including testosterone and DHT. The stereochemistry at C-3 (alpha vs. beta) primarily modulates:

• The relative affinity for androgen receptors and estrogen receptor subtypes.
• The rate and direction of oxidation/reduction by specific 3-HSD isoforms.
• The neurosteroid properties, particularly GABA_A receptor modulation (a property associated primarily with the 3alpha orientation in the fully saturated 5alpha-androstane series).

3.2 The 3alpha-Diol Saturated Analog (Biochemical Context)

Much of what is scientifically established about a C-3alpha-hydroxyl androstane compound relates to 5alpha-androstane-3alpha,17beta-diol (the saturated ring-A version, also called 3alpha-diol or 3alpha-Adiol), which is a well-characterised DHT metabolite. 5alpha-Androstane-3alpha,17beta-diol (3alpha-diol) is reduced from the potent androgen, 5alpha-dihydrotestosterone (5alpha-DHT), by reductive 3alpha-hydroxysteroid dehydrogenases (3alpha-HSDs) in the prostate. 3alpha-diol is recognized as a weak androgen with low affinity toward the androgen receptor (AR), but can be oxidized back to 5alpha-DHT.

The unsaturated (Δ5) 3alpha,17beta-diol form is similarly positioned metabolically as a potential reversible precursor to more potent androgens, though its direct receptor binding data are considerably less well characterised than those of the saturated analog.

4. Mechanisms of Action

4.1 Androgenic Receptor Activity

Androstenediol (as the 3beta,17beta-diol) is less androgenic than the related compound Δ4-androstenediol, and when administered to rats in vivo, it has approximately 1.4% of the androgenicity of DHEA, 0.54% of the androgenicity of androstenedione, and 0.21% of the androgenicity of testosterone. The 3alpha,17beta-diol isomer, being metabolically convertible to the same downstream androgens (testosterone, DHT), may exhibit broadly comparable weak androgenicity, though its direct AR-binding affinity is even less well established in peer-reviewed literature.

Using a transient transfection assay in human prostate cancer cells, androst-5-ene-3beta,17beta-diol can activate androgen receptor (AR) target genes in the presence of AR, and the AR coactivator ARA70 can further enhance this Adiol-induced AR transcriptional activity. Thin layer chromatography analysis reveals that testosterone, dihydrotestosterone, and 17beta-estradiol are undetectable in human prostate cancer DU145 cells after treatment with Adiol, and a proteolysis assay shows that a distinct ligand-receptor conformational difference exists between testosterone-AR and Adiol-AR complexes. This indicates the compound can activate AR directly — not solely through conversion to downstream potent androgens — while producing a distinct receptor conformation.

4.2 Estrogenic Receptor Activity

Androstenediol possesses potent estrogenic activity, similarly to DHEA and 3beta-androstanediol, with approximately 6% and 17% of the affinity of estradiol at the ERalpha and ERbeta, respectively. These affinity values apply specifically to the 3beta,17beta-diol form (Adiol). Androstenediol binds to ERalpha with a Kis of 3.6 nM and to ERbeta with a Kis of 0.9 nM.

The formation of 5-AED is of great biological significance since it binds to both androgen and estrogen receptors, and 5-AED can be called a "hermaphrodiol" due to its high affinity for both of these receptors. This dual receptor activity distinguishes it from most other steroids, which tend to preferentially activate either the androgen or estrogen pathway.

4.3 Conversion to Downstream Androgens and Estrogens

5alpha-androstanediol isomers act as efficient precursors to dihydrotestosterone, converting to DHT via the 3-hydroxysteroid dehydrogenase (3alpha- and 3beta-HSD depending on isomer) and 17beta-hydroxysteroid dehydrogenase enzymes respectively. For the Δ5 (5-ene) isomers, the 3alpha-form is readily interconverted with the 3beta-form and with the corresponding 3-ketone (which can then enter the androstenedione/testosterone axis) by 3-HSD enzymes present in numerous tissues.

Notably, the Δ5-diol metabolic pathway differs from DHEA in the balance of downstream androgen production. Without intending to be bound by theory, one reason DHEA produces a different androgenic response than 5-DIOL at equal dosage is that they are metabolized differently: 5-DIOL's metabolism leads to less formation and/or more inactivation of certain steroids (e.g., testosterone and DHT) before they can exert androgenic activity, thus leading to lower exposure to these potent androgens compared to an equal dose of DHEA.

4.4 NF-κB Signalling and Innate Immunity

A well-characterised mechanism specific to the 3beta,17beta-diol isomer involves the nuclear factor-κB (NF-κB) pathway. 5-AED promotes survival of irradiated human hematopoietic progenitors in vitro through induction of Nuclear Factor-κB (NF-κB)-dependent Granulocyte Colony-Stimulating Factor (G-CSF) expression, and causes elevations of circulating G-CSF and interleukin-6 (IL-6).

This agent is important for innate immunity, serves to modulate cell cycle progression, reduces radiation-induced apoptosis, and regulates DNA repair.

4.5 PI3K/AKT Pathway (Saturated 3alpha-Diol Analog)

For the closely related saturated 5alpha-androstane-3alpha,17beta-diol form, distinct cytoplasmic signalling has been identified. 3alpha-diol may have potent effects by activating cytoplasmic signaling pathways, stimulating AR-independent prostate cell growth, and — more importantly — providing a key signal for androgen-independent prostate cancer progression. Several canonical pathways appeared to be affected by 3alpha-diol-regulated responses in LNCaP cells; among them are apoptosis signaling, PI3K/AKT signaling, and death receptor signaling pathways. Biological analysis confirmed that 3alpha-diol stimulates AKT activation; and the AKT pathway can be activated independent of the classical AR signaling.

Through microarray and bioinformatics analysis, a similar set of 30 responsive genes involving signal transduction, transcription regulation, and cell proliferation were identified in 5alpha-DHT-, 3alpha-diol-, and epidermal growth factor (EGF)-treated samples, with the responsive pattern of these genes more closely related between 3alpha-diol and EGF than between 5alpha-DHT and 3alpha-diol. This indicates that 3alpha-diol is capable of stimulating prostate cell proliferation by eliciting an EGF-like pathway in conjunction with the androgen receptor pathway.

4.6 Neurosteroid Activity

The saturated 3alpha-androstanediol is an endogenous steroid hormone and neurosteroid and a metabolite of androgens like dihydrotestosterone (DHT). It is an inhibitory androstane neurosteroid and weak androgen and estrogen. As a neurosteroid, it acts as a potent positive allosteric modulator of the GABA_A receptor, and has been found to have rewarding, anxiolytic, pro-sexual, and anticonvulsant effects. The 3alpha sterochemistry at C-3 is critical for GABA_A receptor potentiation; the 3beta isomer does not share this property. Relative to its isomer 3beta-androstanediol, which is a potent estrogen, 3alpha-androstanediol has substantially lower, though still significant, affinity for the estrogen receptors, with a several-fold preference for ERbeta over ERalpha. Whether the unsaturated (Δ5) 3alpha,17beta-diol shares neurosteroid GABA_A activity to the same degree as the saturated 5alpha-androstane analog has not been definitively established in the peer-reviewed literature reviewed here.

5. Scientific Evidence by Area of Use

5.1 Radiation Countermeasure / Hematopoietic Protection

This is the most extensively studied area, though essentially all robust data pertain to the 3beta,17beta-diol isomer (5-AED/NEUMUNE) rather than to the 3alpha,17beta-diol form specifically.

Preclinical evidence (animal studies): In laboratory animals of various species, including monkeys, 5-AED demonstrated a pronounced radioprotective effect under conditions of acute and long-term irradiation, as well as under combined exposure to radiation and chemical and biological damaging factors. The drug exhibited anti-radiation properties when injected both before (48–24 hours) irradiation and in the early (1–4 hours) periods after radiation exposure.

In one mouse study, animals were subjected to whole-body irradiation with a sublethal dose of 5 Gy gamma-irradiation to induce severe myelosuppression, and 5-AED (50 mg/kg) was administered subcutaneously — either 1 day before irradiation (pre-treatment) or twice weekly for 3 weeks starting from 1 hour after irradiation (post-treatment). Treatment with 5-AED significantly ameliorated the decrease in the peripheral blood neutrophil and platelet populations in irradiated myelosuppressive mice, but had no effect on the lymphocyte population. It also ameliorated hypocellularity and disruption of bone marrow induced by irradiation and led to rapid recovery of myeloid cells.

A molecular specificity study compared the in vivo radioprotective efficacy of 5-AED (5-androstenediol) to that of ten other steroids including 17alpha-androstenediol, DHEA, 5-androstenetriol (AET), testosterone, and estradiol, among others. Steroids were administered 24 or 48 hours before, or 1 hour after, whole-body gamma-irradiation; blood elements were counted two days after irradiation at 3 Gy, and after irradiation at 9–12.5 Gy, survival was recorded for 30 days. The results showed radioprotective efficacy was specific for 5-AED.

5-Androstenediol significantly ameliorated myeloid suppression, as demonstrated by elevated levels of total white blood cells, including neutrophils and platelets, in the peripheral blood. Additional mechanistic research demonstrated that this agent is important for innate immunity, serves to modulate cell cycle progression, reduces radiation-induced apoptosis, and regulates DNA repair.

Human/clinical evidence: The first stage of clinical trials of NEUMUNE (double-blind randomized trial) was performed on 129 healthy volunteers of different ages and yielded highly promising results. Injections of NEUMUNE showed excellent tolerance and noticeably increased the number of neutrophils and platelets circulating in the peripheral blood. The side effects were negligible, with only a minor local reaction at the injection site.

Findings suggest that parenteral administration of 5-AED in aqueous suspension may be a safe and effective means to stimulate innate immunity and alleviate neutropenia and thrombocytopenia associated with acute radiation syndrome (ARS).

Currently, 5-AED is not used in clinical practice; clinical trials of a 5-AED-based drug were terminated. The experimental drug NEUMUNE, which has a chemical structure of 5-androstenediol (5-AED), was widely studied as a radioprotector and radiomitigator in the USA. However, the trials did not reach the FDA approval phase.

Evidence strength assessment: Preclinical evidence in rodents and non-human primates for the 3beta,17beta-diol isomer is substantial. Human clinical data are limited to Phase I pharmacokinetic/safety studies showing biological activity (elevated neutrophils and platelets). No Phase III efficacy trials in radiation-exposed humans have been completed. Evidence specifically for the 3alpha,17beta-diol isomer in this context is absent from the peer-reviewed literature examined.

5.2 Immunomodulation

Androstenetriol (AET) and androstenediol (AED) upregulate host immunity, leading to increased resistance against infections. AET augments IL-2, IL-3, and IFN-gamma levels, and counteracts hydrocortisone immune suppression.

Androstenediol is a direct metabolite of the most abundant steroid produced by the human adrenal cortex, DHEA, and it has been found to stimulate the immune system. The mechanism of this immune stimulation involves the NF-κB pathway and downstream cytokine production (see Section 4.4). Most data for immunomodulation in humans comes from studies of the NEUMUNE formulation (3beta,17beta-diol form); the 3alpha,17beta-diol form has not been independently investigated for immunomodulatory effects in human trials.

Evidence strength assessment: Mechanistic and animal data support an immunostimulant role for the 3beta,17beta-diol isomer. For the 3alpha,17beta-diol isomer specifically, evidence is preclinical and largely inferential from structural analogy; no independent human immunomodulation trials exist.

5.3 Hormonal / Androgenic and Estrogenic Effects

Androst-5-ene-3beta,17beta-diol (Δ5-Androstenediol), derived from DHEA and convertible into testosterone, has been suggested to play a role in the regulation of immune responses, obesity, and the genesis of estrogen-sensitive carcinomas, such as breast cancer.

The estrogenic effect of Adiol, mediated by the estrogen receptor (ER), has been proposed as an essential female hormone that can partially replace the loss of 17beta-estradiol (E2) for postmenopausal women. Due to the decline in E2 synthesis after menopause, circulating Δ5-androstenediol and 5alpha-androstanediol may be important physiological estrogens in postmenopausal women.

With respect to androgenic activity compared to DHEA, the maximum level of serum DHT reached after 5-DIOL was less than half of the maximum level reached with DHEA, and at relatively low dosage levels, the androgenic effect of 5-DIOL reaches a plateau of maximum activity much lower than that achieved by DHEA. Furthermore, depending on dosage, DHEA is two to five times more potent than 5-DIOL in stimulating prostate binding protein-C1 (PBP-C1) and prostate binding protein-C3 (PBP-C3) mRNA levels, which are particularly sensitive parameters of androgenic action.

Evidence strength assessment: Receptor binding and in vitro evidence for estrogenic and weak androgenic effects of the 3beta,17beta-diol form is well established. Clinical data specifically for the 3alpha,17beta-diol form as an androgenic or estrogenic agent are absent; inference by structural analogy is reasonable but not a substitute for direct study.

5.4 Neurosteroid / Central Nervous System Activity (GABA_A Modulation)

For the saturated analogue 5alpha-androstane-3alpha,17beta-diol, neurosteroid activity is well established. As a neurosteroid, it acts as a potent positive allosteric modulator of the GABA_A receptor, and has been found to have rewarding, anxiolytic, pro-sexual, and anticonvulsant effects. As androgens such as testosterone and DHT are known to have many of the same effects as 3alpha-diol and are converted into it in vivo, it is thought that this compound may in part be responsible for said effects.

The 3alpha sterochemistry at C-3 is a structural prerequisite for GABA_A receptor positive allosteric modulation in the androstane neurosteroid series. Whether the Δ5 (5-ene) unsaturated form of the 3alpha,17beta-diol retains comparable GABA_A activity has not been definitively demonstrated in available peer-reviewed sources reviewed here. The saturated 5alpha-androstane nucleus appears important for optimal GABAergic activity in this steroid class.

Evidence strength assessment: Neurosteroid GABA_A modulation is well established for the saturated 5alpha-androstane-3alpha,17beta-diol form. Direct evidence for the unsaturated Δ5 form is not established in the peer-reviewed literature consulted; any CNS claims for the supplement form rely on structural analogy and are unverified.

5.5 Prostate Cancer Biology

Research on the relationship between androstenediol isomers and prostate cancer has produced important but complex findings, primarily relating to the potential for these steroids to drive cancer cell proliferation:

The first systems-biology approach to demonstrate that 3alpha-diol-activated cytoplasmic signaling pathways are important components of androgen-activated biological functions in human prostate cells showed that, based on the observation that levels of reductive 3alpha-HSD expression are significantly elevated in localized and advanced prostate cancer, 3alpha-diol may therefore play a critical role for the transition from androgen-dependent to androgen-independent prostate cancer in the presence of androgen.

Androst-5-ene-3beta,17beta-diol (AED) is a multi-potent hormone that is an androgen and oestrogen precursor, with the ability to directly transactivate AR and ER in prostate cancer cells. Research has identified inhibitors of AED signalling as potential therapeutic agents. A novel androstane steroid, HE3235 (17alpha-ethynyl-5alpha-androstan-3alpha,17beta-diol), was identified with significant inhibitory activity for AED-stimulated LNCaP proliferation; this inhibitory activity is accompanied by an increase in the number of apoptotic cells; animal studies confirmed the cytoreductive activity of HE3235 on LNCaP tumours; and the results suggest this compound may be of clinical use in castration-resistant prostate cancer.

Evidence strength assessment: The evidence that 3alpha-diol (saturated form) and Δ5-androstenediol (3beta,17beta form) can promote prostate cancer cell proliferation is based on in vitro cell line studies (LNCaP, DU145, PC-3) and in vivo tumour models. There are no human clinical trials of therapeutic utility in prostate cancer for the 3alpha,17beta-diol isomer. The cancer biology data are predominantly preclinical and should be understood as evidence of potential risk rather than therapeutic opportunity.

5.6 Breast Cancer Biology

DNA cell cycle analysis demonstrates that 5-androstene-3beta,17beta-diol stimulates the proliferation of hormone-dependent cell lines at physiological levels by an oestrogen receptor-mediated mechanism, whereas 5alpha-dihydrotestosterone does not affect the proliferation of MCF7 and T47D cell lines at physiological levels over short (48-hour) incubations. Both 5alpha-dihydrotestosterone and 5-androstene-3beta,17beta-diol stimulate proliferation of hormone-dependent cell lines at pharmacological levels via an interaction with the oestrogen receptor. In long (6–9 day) incubations, both 5alpha-dihydrotestosterone and 5-androstene-3beta,17beta-diol inhibit the 17beta-oestradiol-induced proliferation of MCF7 and T47D cell lines.

Evidence strength assessment: In vitro data only; no human clinical trials in breast cancer. The finding of ER-mediated stimulation of hormone-dependent breast cancer cell lines at physiological concentrations is relevant to safety considerations (see Section 7).

6. Body Systems and Health Areas Associated with This Compound

• Endocrine system: Interacts with androgen receptors and both ERalpha and ERbeta; modulates circulating levels of testosterone, estradiol, and DHT through enzymatic interconversion.
• Hematopoietic system: Stimulates recovery of neutrophils and platelets following myelosuppression; promotes innate immune progenitor cell survival via NF-κB/G-CSF axis (evidence from 3beta,17beta-diol isomer).
• Immune system: Modulates cytokine production (IL-2, IL-3, IFN-gamma, IL-6, G-CSF); counteracts glucocorticoid-mediated immune suppression.
• Central nervous system: The saturated 3alpha analog is an established GABA_A positive allosteric modulator; CNS activity of the Δ5 (5-ene) form is less characterised.
• Prostate gland: Both the 3alpha-diol (saturated) and Δ5-androstenediol (3beta form) have documented potential to stimulate prostate cancer cell proliferation through AR and non-AR pathways.
• Reproductive system (female): May serve as a physiological estrogen substitute in postmenopausal women; potential relevance to hormone-sensitive gynecological conditions.
• Musculoskeletal system: Marketed as a performance-enhancer on the basis of weak androgenic activity, though no robust clinical evidence supports meaningful anabolic effects at supplement doses.

7. Dosage Forms and Reported Dosages

Dosage data in the peer-reviewed literature specifically for the 3alpha,17beta-diol isomer are not available; the following data derive from studies of the 3beta,17beta-diol (5-AED/NEUMUNE) isomer:

• Animal studies (subcutaneous): Mice were subjected to whole-body irradiation with a sublethal dose of 5 Gy, and 5-AED at 50 mg/kg was administered subcutaneously.
• Toxicology studies (mice): There were no indications of toxicity in chemical analyses of serum in mice after subcutaneous doses as high as 4,000 mg/kg; at this dose, 2 of 54 mice died when given AED alone. When 4,800 mg/kg was given orally, no deaths resulted.
• Human Phase I trial (injectable): The first stage of clinical trials of NEUMUNE (double-blind randomized trial) was performed on 129 healthy volunteers of different ages; injections showed excellent tolerance, noticeably increased circulating neutrophils and platelets, and the side effects were negligible, with only a minor local reaction at the injection site. Specific mg doses used in the human trial are not disclosed in publicly available abstracts or the review sources consulted.
• Oral bioavailability limitation: Poor oral bioavailability of 5-AED has limited its development as an oral agent, while a variant compound, 17alpha-ethinyl-androst-5-ene-3beta,17beta-diol (EAD), exhibits significant oral bioavailability.

Supplement products containing androstenediol isomers have historically listed doses of approximately 50–200 mg per day in oral and sublingual preparations, based on commercial labelling; however, no robust dose-response human efficacy data exist for such dosage regimens in the peer-reviewed literature.

8. Safety Considerations and Interactions

8.1 Regulatory Status

In October 2004, President George Bush signed the Anabolic Steroid Control Act, which reclassified androstenedione from a supplement to an anabolic steroid, making it and other steroid-based drugs a controlled substance. The 2004 Act also added androstenediol isomers to Schedule III of the Controlled Substances Act in the United States, making their sale and possession without a prescription a federal offence. This effectively removed them from the legal over-the-counter dietary supplement market in the US.

Unlike DHEA, 5-AED is not used as a drug, and no completed clinical trials have been carried out. DHEA itself received FDA approval (as prasterone/Intrarosa) for a specific indication. The experimental drug NEUMUNE (5-androstenediol) was widely studied as a radioprotector and radiomitigator in the USA. However, the trials did not reach the FDA approval phase.

8.2 Hormone-Sensitive Conditions

Because androstenediol isomers can elevate circulating estrogens and androgens through metabolic conversion, hormone-sensitive conditions such as breast cancer, uterine cancer, ovarian cancer, endometriosis, or uterine fibroids represent potential contraindications, as exposure to elevated estrone, estradiol, and testosterone levels could worsen these conditions.

Androstenediol can increase testosterone levels, and there is developing evidence that androstenediol might help prostate cancer cells grow. This is consistent with the preclinical data described in Section 5.5 regarding AR activation and PI3K/AKT pathway stimulation in prostate cancer cell lines.

8.3 Breast Cancer Cell Proliferation Risk

DNA cell cycle analysis demonstrates that 5-androstene-3beta,17beta-diol stimulates the proliferation of hormone-dependent breast cancer cell lines at physiological levels by an oestrogen receptor-mediated mechanism. This in vitro finding is directly relevant to the safety profile of all androstenediol isomers with ER affinity, and represents an unresolved safety concern in the absence of long-term human clinical data.

8.4 Pharmacokinetic Drug Interactions

As steroids metabolised by cytochrome P450 enzymes and hydroxysteroid dehydrogenases, androstenediol isomers are subject to interactions with drugs that alter these enzyme systems. CYP7B1-mediated metabolism of 5alpha-androstane-3alpha,17beta-diol (3alpha-Adiol) represents a novel pathway for potential regulation of androstane metabolism. Compounds that inhibit or induce CYP7B1 and related cytochrome P450 enzymes may therefore alter androstenediol metabolism.

Androstenediol appears to increase estrogen levels in the body; taking androstenediol along with estrogen pills might cause too much estrogen in the body. Such estrogen pills include conjugated equine estrogens (Premarin), ethinyl estradiol, estradiol, and others.

8.5 Sports Doping Status

Androstenediol and its isomers are prohibited substances in competitive sport. The World Anti-Doping Agency (WADA) includes androstenediol in its Prohibited List under endogenous anabolic androgenic steroids (AAS), prohibited both in and out of competition. Administration of exogenous androstenediol produces detectable urinary steroid metabolite ratios that are identifiable by standard anti-doping urine analysis.

8.6 Androgenic/Virilising Effects

Given its convertibility to testosterone and DHT, chronic or high-dose use of androstenediol isomers carries the potential for androgenic side effects including: acne, changes in sebum production, potential for androgenic alopecia in genetically susceptible individuals, alterations in gonadotropin levels (LH, FSH) via negative feedback, and — of particular concern in females — virilisation with prolonged use. These risks are mechanistically predicted from steroid biochemistry and are consistent with the known risks of androstenedione supplementation, for which more extensive human data exist.

9. Evidence Summary and Limitations

The scientific literature on 5-androstene-3alpha,17beta-diol as a distinct molecular entity is sparse. The preponderance of published research on "androstenediol" or "5-androstenediol" pertains to the 3beta,17beta-diol isomer (5-AED/NEUMUNE). The most robust finding in that literature — radioprotective and hematopoietic-stimulant activity — reached Phase I human trials without progressing to FDA approval, representing promising but incomplete evidence.

For the 3alpha,17beta-diol form specifically, peer-reviewed evidence is limited primarily to: its identification as an endogenous DHEA metabolite; receptor-binding characterisation in relation to AR and ER; and mechanistic studies (PI3K/AKT, EGF-like signalling) performed on the saturated analog (5alpha-androstane-3alpha,17beta-diol) in prostate cancer cells. No independent clinical trials of the isolated 3alpha,17beta-diol form exist in the sources reviewed.

Claims made in the dietary supplement market for the 3alpha,17beta-diol form — including muscle building, testosterone elevation, and immune enhancement — are largely extrapolated from studies of structurally related steroids and from the pharmacology of the better-studied 3beta counterpart. These claims are not supported by independent human clinical evidence for this specific isomer.

References

• Wikipedia: Androstenediol (Androst-5-ene-3β,17β-diol)
• Wikipedia: 3α-Androstanediol (5α-Androstane-3α,17β-diol)
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