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High riskCardiotoxicNeuropsychiatric

Trenbolone Hexahydrobenzylcarbonate

Parabolan · Tren Hex

Trenbolone hexahydrobenzylcarbonate (Parabolan, "Tren Hex") is a long-acting injectable ester of trenbolone, a synthetic 19-nortestosterone (nandrolone-derived) anabolic-androgenic steroid (AAS). The ester only slows release; the active drug is trenbolone, which binds the androgen receptor with roughly three times the affinity of testosterone and is not aromatized to estradiol. It is used non-medically to increase muscle mass and reduce fat, and has never been established as safe in controlled human trials. There is essentially no controlled human safety data for trenbolone; the human record is limited to case reports and one survey. Documented harms include severe cholestatic liver injury (jaundice with bilirubin over 60 mg/dL requiring liver-support therapy), acute pancreatitis, hypercalcemia with acute kidney injury, erythrocytosis (thickened blood), hypertension and cardiac arrhythmia, marked suppression of the hypothalamic-pituitary-testicular axis with testicular atrophy and infertility, gynecomastia and severe acne in roughly one third of users, and dose-related aggression. Reviews report that about 90% of trenbolone users experience adverse effects. This substance is high-risk; anyone using or considering it should be under the care of a physician with regular bloodwork.

Clinical readoutAAS · injectable-19nor
Hepatic strainHigh
CardiovascularHigh
HPTA suppressionVery high
Half-life
No human pharmaco…
Route
Intramuscular oil-based…
Evidence
B
Active
Long-acting depot
1·t½2·t½3·t½4·t½5·t½
Illustrative single-compartment washout · each mark = one half-life · t½ ≈ No human pharmacokinetic study of the hexahydrobenzylcarbonate ester was identified. The parent hormone trenbolone has a short intrinsic half-life; the hexahydrobenzylcarbonate (cyclohexylmethyl carbonate) ester is a long-chain ester that creates an intramuscular depot, giving an effective release half-life on the order of days (functionally intermediate-to-long, broadly comparable to enanthate/cypionate esters). Exact human values are not established.
Pharmacology

Mechanism of action

Trenbolone is a potent full agonist of the androgen receptor (AR), binding with approximately three times the affinity of testosterone and producing strong AR activation in mammalian-cell bioassays. Unlike testosterone it is not a substrate for aromatase, so it does not convert to estradiol, and it is metabolized to weaker rather than stronger androgens, which underlies its relatively high anabolic-to-classical-androgenic ratio in preclinical models. It increases skeletal muscle protein accretion and bone growth and reduces adiposity in multiple mammalian species. As a 19-nortestosterone derivative it also has progestogenic activity at the progesterone receptor, which is the proposed mechanism for gynecomastia despite the absence of aromatization. Suppression of endogenous gonadotropin (LH/FSH) secretion and testicular testosterone production follows from potent negative feedback on the HPTA. The hexahydrobenzylcarbonate ester is cleaved to release free trenbolone; it does not change the pharmacology, only the rate of release.
Kinetics

Pharmacokinetics

Half-life

No human pharmacokinetic study of the hexahydrobenzylcarbonate ester was identified. The parent hormone trenbolone has a short intrinsic half-life; the hexahydrobenzylcarbonate (cyclohexylmethyl carbonate) ester is a long-chain ester that creates an intramuscular depot, giving an effective release half-life on the order of days (functionally intermediate-to-long, broadly comparable to enanthate/cypionate esters). Exact human values are not established.

Active duration

Long-acting depot; biological activity persists roughly 1-2 weeks per injection based on ester chemistry (no primary human data). Clinically relevant for washout before surgery, pregnancy planning, or lab interpretation.

Route

Intramuscular oil-based injection (confirmed in human case reports).

Metabolism & clearance

After ester cleavage, trenbolone undergoes hepatic metabolism to metabolites including epitrenbolone and trendione, excreted in urine and bile; it is not aromatized. Metabolites are detectable for a prolonged period. This information is provided for clinical monitoring and washout, not for evading testing. Human clearance parameters are not well characterized.

For monitoring and washout planning, not drug-test evasion.

Reported effects

Physiological & performance effects

  • Increases skeletal muscle mass and strength and reduces body fat in mammalian models (no controlled human efficacy trials)
  • Binds the androgen receptor ~3x more strongly than testosterone and is a strong AR agonist
  • Not aromatized to estrogen, but retains progestogenic (19-nor) activity
  • Users commonly report rapid changes in body composition; reviews estimate ~90% of trenbolone users experience adverse effects alongside any perceived benefits
  • Higher trenbolone dose is statistically associated with greater verbal aggression among male AAS users
Safety

Adverse effects by system

Cardiovascular

Trenbolone-specific controlled data are absent. A human review of trenbolone reports hypertension and cardiac arrhythmia among users. Extrapolated from general AAS cohorts: chronic supraphysiologic AAS use is associated with left ventricular hypertrophy, left atrial myocardial dysfunction, and subclinical left-ventricular systolic dysfunction (reduced global longitudinal strain) that can persist off-cycle despite a normal ejection fraction. Adverse lipid shifts are expected with non-aromatizing androgens. Treat as high cardiovascular risk.

Hepatic

Trenbolone is not 17-alpha-alkylated, so classic oral-steroid hepatocellular toxicity is less expected; nonetheless severe cholestatic liver injury is documented. A 21-year-old using Parabolan (trenbolone) developed profound cholestasis with serum bilirubin up to 65.5 mg/dL, unresponsive to supportive care and requiring molecular adsorbent recirculating system (MARS) therapy. Acute pancreatitis, recurring on rechallenge, has also been attributed to trenbolone acetate.

Endocrine / HPTA

Potent, expected suppression of the hypothalamic-pituitary-testicular axis (reduced LH/FSH and endogenous testosterone), consistent with the AAS class; documented as anabolic-steroid-induced hypogonadism (ASIH). Gynecomastia occurs in roughly one third of users, attributed to progestogenic (19-nor) activity rather than aromatization. Onset, depth, and duration of suppression are individual and can be prolonged.

Reproductive

Testicular atrophy, impaired spermatogenesis, and infertility are recognized consequences of AAS use including 19-nor compounds; gynecomastia is common. Preclinical work shows trenbolone binds the AR and disrupts gonadal/sexual differentiation and germ-cell number in fish and rodents. Human fertility recovery is variable and not guaranteed.

Neuropsychiatric

In a cross-sectional survey of 282 male AAS users, higher trenbolone dose was independently associated with greater verbal aggression after adjustment for age and BMI; the study also examined psychological distress. Human reviews describe nervous-system and behavioral effects. Widely reported insomnia, night sweats, anxiety, and mood lability are anecdotal with no controlled human data. Treat neuropsychiatric change as a warning sign.

Renal

A trenbolone user developed severe hypercalcemia (15 mg/dL) with acute kidney injury (creatinine 6.02 mg/dL) after malignancy, hyperparathyroidism, and vitamin D toxicity were excluded, improving with fluids and pamidronate. Forensic review of AAS abuse links long-term use to renal disease. Data are limited to case reports.

Hematologic

Erythrocytosis (elevated hematocrit/polycythemia) is documented in a trenbolone user, consistent with androgen-driven stimulation of erythropoiesis; this raises blood viscosity and thrombotic risk. An oil-vehicle steroid injection also produced pseudohyponatremia as a laboratory artifact. No trenbolone-specific controlled hematologic data exist.

Dermatologic

Severe acne affects approximately one third of users; reported dermatologic effects also include stretch marks and excessive body hair. Injection-site local inflammation, fibrosis, muscle adhesions, and in extreme cases tissue necrosis are described, compounded by product contamination in illicit supply.

Recovery

HPTA suppression & recovery

Suppression: Marked/severe and expected; can be prolonged

As a potent, progestogenic 19-nortestosterone androgen, trenbolone strongly suppresses LH/FSH and endogenous testosterone, producing anabolic-steroid-induced hypogonadism (ASIH). Recovery is individual and not guaranteed; time to normalization depends on dose, duration, and agents used. No high-quality trials define an optimal recovery approach (a planned meta-analysis found no studies meeting inclusion criteria). Any post-use recovery, including consideration of a single selective estrogen receptor modulator (SERM), must be directed and monitored by an endocrinologist or andrologist with baseline and follow-up hormone testing; this monograph does not endorse any self-managed hormonal protocol. Persistent hypogonadal symptoms warrant specialist referral rather than self-treatment.

Bloodwork & vitals

Monitoring

Recommended labs & checks
CBC with hematocrit/hemoglobin (erythrocytosis)Liver panel including total/direct bilirubin, ALT, AST, ALP, GGTLipase (if abdominal pain, to assess pancreatitis)Renal function: creatinine, eGFR, electrolytesSerum calcium (and albumin/ionized calcium if abnormal)Fasting lipid panelReproductive hormones: LH, FSH, total testosterone, estradiol, prolactinPSA in older menBlood pressure at every visitECG and echocardiography with global longitudinal strain if cardiac symptoms or long-term use

Cadence: Baseline before any use, then periodic monitoring (e.g., approximately every 3 months during use and during any post-use recovery) and promptly whenever warning signs appear; all under a supervising clinician.

Warning signs — seek care
  • Jaundice, dark urine, pale stools, or itching (cholestasis)
  • Severe upper abdominal pain radiating to the back (possible pancreatitis)
  • Chest pain, breathlessness, palpitations, or fainting
  • Leg swelling, sudden severe headache, or signs of clot/stroke
  • Markedly elevated blood pressure
  • Reduced urine output, severe fatigue, confusion (kidney injury/hypercalcemia)
  • Severe mood change, aggression, depression, or suicidal thoughts
  • Rapidly worsening acne, breast tissue growth, or testicular shrinkage
Do not use if

Contraindications

  • Pre-existing cardiovascular disease, hypertension, or cardiomyopathy
  • Hepatic impairment or prior cholestatic/drug-induced liver injury
  • Polycythemia or elevated hematocrit / prothrombotic states
  • Renal impairment or history of hypercalcemia/AKI
  • Known or suspected hormone-sensitive cancer (prostate, breast)
  • History of acute pancreatitis
  • Significant psychiatric illness, mood disorder, or aggression/impulse-control problems
  • Pregnancy, breastfeeding, and women generally (virilization, some effects irreversible)
  • Adolescents and anyone with open growth plates
  • Men seeking to preserve current or near-term fertility
  • Concurrent hepatotoxic or thrombogenic medications
Combinations

Interaction profile

  • MajorWith another anabolic steroid: Additive cardiovascular strain
  • MajorWith a thermogenic stimulant: Additive cardiovascular strain
  • ModerateWith thyroid hormone: Additive cardiovascular strain
  • ModerateWith growth hormone: Additive cardiovascular strain
  • MajorWith another anabolic steroid: Blood / clotting
  • MajorWith a clot-promoting SERM: Blood / clotting
  • ModerateWith an aromatase inhibitor: Hormonal
  • ModerateWith an anabolic steroid: Hormonal
  • ModerateWith another 19-nor (progestogenic) steroid: Hormonal
  • ContraindicatedWith DNP: Additive cardiovascular strain

Check a specific combination in the interaction checker.

Harm reduction

Reducing harm & when to stop

  • There is no controlled human safety data for trenbolone; individual risk cannot be reliably predicted, and reviews estimate ~90% of users experience adverse effects.
  • Do not use without a physician aware of the use; establish baseline bloodwork (CBC/hematocrit, liver, renal, calcium, lipids, hormones, blood pressure) before and during any exposure.
  • Stop and seek urgent medical care for jaundice, dark urine or itching (liver), severe abdominal pain radiating to the back (pancreatitis), chest pain, breathlessness, palpitations or fainting, reduced urine output or confusion (kidney/calcium), or severe mood change, aggression, or suicidal thoughts.
  • Rising hematocrit thickens the blood and raises clot/stroke risk. Do not ignore it: medical evaluation is needed and use should stop.
  • Injection-site pain, redness, swelling, or spreading infection requires medical assessment; illicit products are frequently contaminated or mislabeled (some 'Parabolan' has contained trenbolone acetate).
  • This monograph does not provide dosing to maximize effect; any clinical dose range in the literature is inseparable from the harms above.
  • For HPTA recovery, do not self-manage: see an endocrinologist or andrologist. Recovery is individual and may be incomplete, and fertility should not be assumed to return.
  • Women, adolescents, and anyone pregnant or planning pregnancy should not use trenbolone; some virilizing effects are irreversible.
Evidence

Citations (14)

Every clinical claim above is tied to a primary source. Overall evidence grade B — graded to the best available evidence for its core claims.

  1. 01

    Trenbolone binds the androgen receptor with ~3x the affinity of testosterone, is not aromatized to estradiol, is metabolized to weaker androgens, and increases muscle and bone while reducing adiposity in mammalian models (mechanism, SARM-like profile).

    ReviewTissue selectivity and potential clinical applications of trenbolone (17beta-hydroxyestra-4,9,11-trien-3-one): A potent anabolic steroid with reduced androgenic and estrogenic activity.PMID 20138077 ↗

  2. 02

    Beta-trenbolone is a strong androgen-receptor agonist in a mammalian (HEK293) cell bioassay, more potent than testosterone.

    PreclinicalUnravelling androgens in sport: Altrenogest shows strong activation of the androgen receptor in a mammalian cell bioassay.PMID 33037724 ↗

  3. 03

    Trenbolone review: about 90% of users experience adverse effects; severe acne and gynecomastia affect ~one third of users; excessive body hair, stretch marks, hypertension and cardiac arrhythmia occur; injection-site inflammation, fibrosis, adhesions, nerve damage and necrosis, plus product contamination.

    ReviewImpact of trenbolone on selected organs.PMID 38887114 ↗

  4. 04

    Higher trenbolone dose is independently associated with greater verbal aggression among male AAS users (cross-sectional survey, n=282), with assessment of psychological distress.

    CohortExamining the association between trenbolone, psychological distress, and aggression among males who use anabolic-androgenic steroids.PMID 39486244 ↗

  5. 05

    Severe cholestasis (bilirubin up to 65.5 mg/dL) in a 21-year-old bodybuilder using Parabolan/trenbolone, requiring MARS liver-support therapy.

    Case reportCholestasis induced by parabolan successfully treated with the molecular adsorbent recirculating system.PMID 16436902 ↗

  6. 06

    Acute pancreatitis attributed to trenbolone acetate, recurring on rechallenge with the same drug.

    Case reportAcute pancreatitis secondary to the use of the anabolic steroid trenbolone acetate.PMID 30101635 ↗

  7. 07

    Trenbolone use associated with severe hypercalcemia (15 mg/dL) and acute kidney injury (creatinine 6.02 mg/dL) after excluding malignancy, hyperparathyroidism and vitamin D toxicity.

    Case reportHypercalcemia From Trenbolone Use: A Case Report.PMID 41769525 ↗

  8. 08

    Erythrocytosis consistent with anabolic steroid use, and pseudohyponatremia as a lab artifact, following intramuscular trenbolone injection.

    Case reportWhen the Numbers Lie: Uncovering Pseudohyponatremia After an Anabolic Steroid Injection.PMID 41492630 ↗

  9. 09

    Fatal case involving long-term multi-agent AAS use including trenbolone; long-term AAS abuse linked to cardiac, hepatic and renal disease.

    Case reportThe Power of Keratinous Matrices (Head Hair, Body Hair and Nail Clippings) Analysis in a Case of Death Involving Anabolic Agents.PMID 36516229 ↗

  10. 10

    Chronic AAS abuse is associated with left ventricular hypertrophy and left atrial myocardial dysfunction (extrapolated class evidence, not trenbolone-specific).

    CohortLeft atrial myocardial dysfunction after chronic abuse of anabolic androgenic steroids: a speckle tracking echocardiography analysis.PMID 29790034 ↗

  11. 11

    Chronic AAS use produces subclinical left-ventricular systolic dysfunction (reduced global longitudinal strain) persisting off-cycle despite normal ejection fraction, with septal/posterior wall thickening (extrapolated class evidence).

    CohortChronic anabolic androgenic steroid administration reduces global longitudinal strain among off-cycle bodybuilders.PMID 37003371 ↗

  12. 12

    AAS use causes anabolic-steroid-induced hypogonadism and male infertility; recovery of spermatogenesis is variable and managed with endocrine therapy under specialist care.

    ReviewAnabolic steroid misuse and male infertility: management and strategies to improve patient awareness.PMID 33973822 ↗

  13. 13

    Anabolic-steroid-induced hypogonadism (ASIH): diagnosis and treatment; a planned meta-analysis found no studies meeting quality inclusion criteria, underscoring the weak evidence base and need for specialist management.

    ReviewAnabolic steroid-induced hypogonadism: diagnosis and treatment.PMID 24636400 ↗

  14. 14

    Trenbolone binds the androgen receptor and disrupts gonadal/sexual differentiation and reduces primordial germ-cell number (preclinical, zebrafish).

    Preclinical17beta-Trenbolone binds to androgen receptor, decreases number of primordial germ cells, modulates expression of genes related to sexual differentiation, and affects sexual differentiation in zebrafish (Danio rerio).PMID 34662611 ↗

Last reviewed 2026-07-06 · Verified against PubMed · Educational, not medical advice