Tetrahydrogestrinone
THG, The Clear
Oral steroidsControlled substanceWADA S1.1 · prohibitedEvidence: animal data only
A designer steroid made from the progestin gestrinone, found in 2003 in a spent syringe and in athletes' samples. A potent androgen and progestin in lab tests; never studied in people.
Legal status: Never approved; a named Schedule III anabolic steroid in the US and controlled in many countries; varies by country.
What it gives
What people use it for and what the sources report. Strength is a general category from the literature: mild, clear or strong.
Purpose
Made to be invisible to doping tests and supplied to elite athletes through the BALCO lab; its discovery in 2003 led to suspensions. Users sought muscle, strength and recovery. It has no medical use.
What people seek and what studies show
Evidence is from lab and animal work only. In yeast assays it strongly activated androgen and progesterone receptors; it also binds glucocorticoid and mineralocorticoid receptors, the glucocorticoid one most tightly. In mice it enlarged muscle and prostate with about a fifth of DHT's potency. No human data on muscle, strength or safety exist.
Effects
Evidence: Animal data only — effects in people are unproven
Sought effects by goal (as reported)
Mass
Sought for: muscle growth, strength, recovery
Recomposition
Sought for: muscle growth
Strength
Sought for: strength, recovery, muscle growth
Endurance
Sought for: recovery
Recovery & healing
Sought for: recovery
Possible side effects
Possible does not mean certain: whether they appear depends on dose, duration, individual response and monitoring. Below — what to watch for and how to notice it early.
16 possible side effects
level · how often it is reportedElevated
Suppression of natural testosterone & fertility
commonAs a potent androgen and progestin it is expected to strongly suppress natural testosterone and sperm production; human data are lacking.
How to notice: Lower libido and energy, smaller testicles; low natural testosterone on tests after stopping.
In women: Menstrual changes or missed periods, lower libido and energy; reduced fertility.
Elevated
Worse cholesterol (HDL↓ LDL↑)
commonA potent androgen that forms no estrogen: a marked HDL drop is expected, though no human data exist. Only a lipid panel shows it.
How to notice: No symptoms — only visible on a lipid panel.
Elevated
Liver strain
possibleCarries a 17α-ethyl group and in rats disturbed glucocorticoid-controlled gene activity in the liver; no human liver data exist. A liver panel checks it.
How to notice: Usually silent early; later tiredness, nausea, itch, dark urine.
Elevated
Kidney strain
rareRare: as with other 17α-alkylated oral steroids, severe cholestasis can injure the kidneys; no THG-specific data exist.
How to notice: Usually silent; foamy urine or swelling in later stages.
Moderate
Black-market quality risk (fakes, contamination)
commonNever a medicine: any product is clandestine, with unknown content and purity.
How to notice: Unexpected effects, pain or infection, a stronger or weaker effect than expected.
Moderate
High prolactin / progestogenic effects
possibleA highly potent progestin in lab tests; human data on prolactin or nipple symptoms are lacking, but progestogenic effects are possible.
How to notice: Lower libido, weaker erections, nipple sensitivity or discharge.
Moderate
Higher blood pressure
possibleAndrogens can raise blood pressure, and it also binds the mineralocorticoid receptor in lab tests; home readings show the trend.
How to notice: Often silent; sometimes headaches, flushing, nosebleeds — a home monitor shows it.
Moderate
Thick blood (hematocrit) / clot risk
possibleNo human data, but potent androgens raise red-cell production; a blood count tracks hematocrit.
How to notice: Often silent; sometimes headaches, flushed face, itch after a hot shower.
Moderate
Heart strain / heart-muscle thickening
possibleLower HDL and higher blood pressure add strain on the heart; years of AAS use are linked to heart-muscle changes.
How to notice: Shortness of breath on effort, lower endurance, palpitations.
Moderate
Irritability, aggression, mood swings
possibleNo specific data; potent androgens such as trenbolone, its close chemical relative, are linked to irritability and aggression.
How to notice: Short temper, irritability, conflicts with others.
Moderate
Acne, oily skin
possibleStrongly androgenic: oily skin and acne are likely.
How to notice: Oily skin, spots on back, shoulders and face.
Moderate
Androgenic hair loss
possibleStrongly androgenic: can speed up genetic hair loss.
How to notice: More hair in the shower, thinning at the temples or crown.
Moderate
Unknown long-term safety (little human data)
possibleNever tested in people; everything known comes from lab and animal studies.
How to notice: Nothing to notice — the risk is what is not yet known.
Moderate
Abnormal tissue growth (theoretical cancer risk)
rareIn cell tests it caused chromosome errors (micronuclei) at low concentrations, as trenbolone did; whether this matters in people is unknown.
How to notice: No direct signs — the point is not to fuel existing growths.
MenLow
WomenHigh
Virilization in women (often irreversible)
commonA potent androgen and progestin: in women voice deepening, facial hair, clitoral enlargement and menstrual changes are expected and may be permanent.
How to notice: Hoarse or deeper voice, new facial or body hair, menstrual changes, clitoral enlargement.
Low
Too-low estrogen (joints, libido, mood, lipids)
possibleHas no estrogenic activity: used without testosterone it can leave estradiol low — low libido, flat mood and joint aches can follow.
How to notice: Aching, stiff joints, low libido, flat mood, poor sleep.
What the levels mean
Lowbackground — just be aware
Moderatewatch for signs
Elevatedneeds regular control
Highcritical — can be life-threatening or permanent
Level: general category from the literature, not your personal risk
How often
- common
- reported often
- possible
- reported in some people
- rare
- reported occasionally
How to lower the risks
For 13 of 16 possible side effects there are specific ways to lower the chance: everyday measures, supplements and options a doctor may consider. For the rest — general advice. No measure removes a risk completely. Prescription medicines are listed only for a doctor to decide on, after tests — they have side effects of their own.
ElevatedSuppression of natural testosterone & fertility
Check hormones before and after; if they stay low, see an endocrinologist.
Measure
Only if a doctor prescribes
How each option helps (7)
- Regular blood tests — LH, FSH and testosterone show how deep suppression is and whether natural production has recovered afterwards.
- Working with a doctor — Assesses how deep suppression is and guides recovery afterwards, including fertility testing.
- Clomiphene — A doctor may consider it after stopping, guided by hormone tests; recovery after long use can still take months. Risks: vision changes, mood swings, rare clots. Has side effects of its own.
- Human chorionic gonadotropin (hCG) — A doctor may consider it to preserve fertility (in men it keeps the testes working); it does not restart the pituitary, so natural LH still has to recover. Risks: higher estradiol, gynecomastia. Has side effects of its own.
- Tamoxifen — A doctor may consider it after steroids are stopped, guided by hormone tests; it has not been tested for this after steroid use. Risks: blood clots, vision changes. Has side effects of its own. Not offered to women: in the women’s view it adds to a risk this substance already carries.
- Follicle-stimulating hormone (follitropins, menotropins) — A fertility doctor may consider adding it to hCG when semen tests and FSH stay low; it does not restart the pituitary. Risks: gynecomastia, acne. Has side effects of its own.
- Toremifene — A doctor may consider it after steroids are stopped, guided by hormone tests; it raised testosterone in subfertile men but was never tested after steroids. Risks: QT prolongation, clots. Has side effects of its own. Not offered to women: in the women’s view it adds to a risk this substance already carries.
ElevatedWorse cholesterol (HDL↓ LDL↑)
Avoid combining several oral steroids; regular cardio, soluble fiber (psyllium), less saturated fat and alcohol; if LDL/ApoB stay high, a doctor may consider a statin. Omega-3 only lowers triglycerides.
Measure
Supplement or OTC product
Only if a doctor prescribes
How each option helps (12)
- Regular blood tests — A lipid panel with ApoB shows how far HDL has dropped and LDL risen — changes you cannot feel.
- Working with a doctor — Interprets lipids and ApoB and decides whether a statin or other therapy is warranted.
- Avoiding alcohol and other liver stressors — Alcohol raises triglycerides; its small HDL bump does not lower heart risk.
- Regular cardio training — Raises HDL a little and lowers triglycerides; it cannot offset a steroid-driven fall in HDL on its own.
- Berberine — Placebo-controlled meta-analysis: LDL about 0.5 and triglycerides about 0.4 mmol/L lower; HDL unchanged. Trials are mostly small; no statin substitute.
- Citrus bergamot — Pooled small trials show lower LDL and triglycerides, but certainty is low to very low; it is no replacement for statins.
- Omega-3 (fish oil, EPA/DHA) — Clearly lowers triglycerides but does not fix the steroid HDL drop, the main lipid harm; DHA-containing oils may even raise LDL slightly.
- Psyllium husk fiber — Lowers LDL by about 0.2–0.3 mmol/L (roughly 5–10%), also on top of doctor-prescribed statins; no effect on HDL.
- Atorvastatin — A doctor may consider it when LDL or ApoB stay high; it strongly lowers them but barely lifts steroid-lowered HDL. Risks: muscle aches, drug interactions, rarely muscle or liver injury. Has side effects of its own.
- Rosuvastatin — A doctor may consider it when LDL or ApoB stay high; it strongly lowers them but barely lifts steroid-lowered HDL. Risks: muscle aches, rarely muscle or liver injury, slightly higher diabetes risk. Has side effects of its own.
- Ezetimibe — A doctor may consider it when LDL stays high on a statin or a statin isn't tolerated; it lowers LDL moderately but does not raise HDL. Risks: rare liver-enzyme rises. Has side effects of its own.
- Pravastatin / pitavastatin (low-interaction statins) — A doctor may consider them when LDL is high and other statins aren't tolerated; they lower LDL moderately and barely lift HDL. Risks: muscle aches, slightly higher diabetes risk. Has side effects of its own.
ElevatedLiver strain
No alcohol, no other liver stressors, limit oral steroids and their combinations, check liver enzymes.
Measure
Supplement or OTC product
Only if a doctor prescribes
How each option helps (6)
- Avoiding alcohol and other liver stressors — Removes a major extra liver stressor during oral steroids and other hepatotoxic drugs.
- Regular blood tests — ALT, AST, GGT and bilirubin show liver strain before symptoms; heavy lifting alone raises AST/ALT for days, and GGT helps tell muscle from liver.
- Ademetionine (SAMe) — Used for intrahepatic cholestasis in some countries, but trials are small and of low quality; untested in steroid users. Stopping the oral steroid matters most.
- N-acetylcysteine (NAC) — Restores glutathione; proven in paracetamol poisoning and helped in early acute liver failure of other causes, but untested in steroid users.
- TUDCA (tauroursodeoxycholic acid) — Improves bile flow in cholestatic disease; in steroid cholestasis only case reports, with failures in severe cases. Stopping the oral steroid matters most.
- Ursodeoxycholic acid (UDCA) — A doctor may consider it to improve bile flow; in steroid cholestasis benefit is unproven and severe cases often did not respond. Stopping the oral steroid comes first. Has side effects of its own.
ElevatedKidney strain
Drink enough water, control blood pressure, avoid regular painkillers (NSAIDs).
Measure
Only if a doctor prescribes
How each option helps (6)
- Fluid & electrolyte management — Good hydration eases kidney stress from heavy training and heat; dehydration plus NSAIDs is a classic cause of acute kidney injury.
- Regular blood tests — Creatinine reads high in muscular people and with creatine; cystatin C and a urine test give a truer picture of the kidneys.
- Working with a doctor — Investigates protein in the urine or falling kidney function and can start treatment that slows kidney damage.
- ACE inhibitors (ramipril, perindopril, lisinopril) — May reduce protein leakage into urine and slow kidney disease. But with dehydration, diuretics or NSAIDs (ibuprofen etc.) they can trigger acute kidney injury. Has side effects of its own.
- Losartan / valsartan (angiotensin receptor blockers) — May reduce protein leakage into urine. But with dehydration, water cuts, diuretics or NSAIDs (ibuprofen etc.) they can trigger acute kidney injury. Has side effects of its own.
- Telmisartan — May reduce protein leakage into urine. But with dehydration, diuretics or NSAIDs (ibuprofen etc.) it can trigger acute kidney injury. Has side effects of its own.
ModerateBlack-market quality risk (fakes, contamination)
Products obtained without a prescription are often fake, mislabeled or non-sterile, and there is no way to check at home. For legal supplements, look for third-party testing (Informed Sport, NSF).
ModerateHigh prolactin / progestogenic effects
Test prolactin if libido drops; a doctor decides on correction.
Measure
How each option helps (1)
- Regular blood tests — Prolactin testing matters with 19-nor compounds and helps explain low libido or nipple discharge.
ModerateHigher blood pressure
Less salt, regular cardio, good sleep; home readings; a doctor if it stays high.
Measure
Supplement or OTC product
How each option helps (8)
- Home blood-pressure monitoring — Seated, rested readings on several days show your true BP; persistently high values are a signal to see a doctor.
- Regular cardio training — Regular aerobic training lowers resting BP by a few mmHg, more in people with high BP.
- Working with a doctor — Diagnoses persistent hypertension and prescribes treatment when needed.
- Avoiding alcohol and other liver stressors — Regular drinking raises blood pressure; cutting it out lowers it.
- Coenzyme Q10 — Inconsistent: some analyses show a small systolic drop in cardiometabolic disease, but a Cochrane review found no clinically meaningful effect.
- Magnesium — Meta-analysis of trials: about 2 mmHg lower systolic pressure on average.
- Omega-3 (fish oil, EPA/DHA) — Small drop of a few mmHg, mainly in people with untreated high blood pressure.
- Taurine — Meta-analysis of 20 small trials: about 4 mmHg lower systolic pressure on average.
ModerateThick blood (hematocrit) / clot risk
Check the blood count regularly; if hematocrit stays high, a doctor decides — usually stopping or reducing the cause, sometimes therapeutic phlebotomy, never blood-bank donation. Avoid dehydration: it thickens the blood further.
Measure
How each option helps (3)
- Regular blood tests — A blood count shows hematocrit and hemoglobin climbing toward the range where clot and stroke risk rises.
- Therapeutic phlebotomy prescribed by a doctor — Only on a doctor's decision, never at a blood bank. Lowers hematocrit quickly but temporarily; repeated sessions drain iron, and a lower clot risk is unproven.
- Working with a doctor — Manages thick blood by changing what you use or, if justified, by therapeutic phlebotomy.
ModerateHeart strain / heart-muscle thickening
Regular cardio, blood pressure control, an echo as a baseline and then yearly.
Measure
How each option helps (4)
- Heart screening: ECG and echocardiogram — Echocardiography shows wall thickening and reduced pumping early, while stopping AAS and treating BP can still help.
- Working with a doctor — Orders ECG and echocardiography and treats early heart changes.
- Home blood-pressure monitoring — Keeping BP controlled is one of the main ways to limit heart-wall thickening.
- Regular cardio training — Supports heart and vessel function, but does not reverse steroid-related heart thickening or weakening.
ModerateIrritability, aggression, mood swings
Good sleep, fewer stressors, tell someone close to you what to watch for.
Measure
How each option helps (2)
- Avoiding alcohol and other liver stressors — Alcohol and other drugs on top of steroids explain much of the link between steroid use and violence.
- Sleep hygiene — Enough sleep lowers irritability and improves impulse control.
ModerateAcne, oily skin
Gentle skin care, cleansing after training, a dermatologist if it spreads.
Supplement or OTC product
How each option helps (3)
- Adapalene — Reduces spots in many users. Redness, scaling, dryness and stinging are common early and usually ease; acne may look worse at first. Rarely, allergic swelling.
- Benzoyl peroxide — A first-line acne option. Dryness, redness and peeling are common at first; it bleaches hair and fabric; rarely, serious allergic reactions. Severe steroid acne needs a dermatologist.
- Zinc — Trials show a modest drop in inflamed spots, weaker than antibiotics; steroid acne is driven by androgens.
ModerateAndrogenic hair loss
Ketoconazole shampoo, minoxidil, a dermatologist early if you are prone to it.
Supplement or OTC product
How each option helps (1)
- Minoxidil (topical) — Slows thinning and regrows some hair; scalp itching and early temporary shedding are common, unwanted facial hair possible. Gains fade once stopped.
ModerateUnknown long-term safety (little human data)
What is unknown cannot be lowered, only avoided; tell your doctor what you have taken.
ModerateAbnormal tissue growth (theoretical cancer risk)
No check-up or blood test lowers this risk; avoid with any personal or family history of cancer.
MenLow
WomenHigh
Stop at the first voice change and see a doctor — early stopping matters.
Measure
How each option helps (1)
- Working with a doctor — Steroid labels say to stop at the first mild signs (hoarse voice, facial hair, clitoral growth) to prevent permanent change; checks catch them early but do not make use safe.
Low-level side effects
Low estrogen
Avoid controlling estrogen blindly; adjust only by blood tests with a doctor.
Measure
How each option helps (1)
- Regular blood tests — Testing ends guesswork use of aromatase inhibitors — prescription drugs that can push estrogen too low and harm joints, libido, mood and lipids.
Check-ups and blood tests
Which tests and check-ups to do and when. This is a guide — agree the exact schedule with your doctor.
Baseline tests
your own starting values — every later result is compared with them
Lipid panel (HDL, LDL, triglycerides, ApoB)cholesterol, low estrogen
Liver panel (ALT, AST, GGT, bilirubin)liver
Complete blood count (hematocrit, hemoglobin)hematocrit
Kidney panel (creatinine, eGFR, cystatin C)kidneys, blood pressure
Testosterone (total, free), LH, FSH, SHBGnatural testosterone, libido
Estradiol (sensitive assay)low estrogen, libido
Prolactinprolactin, libido
Home blood-pressure logkidneys, blood pressure, heart
ECGheart
Echocardiogram (heart ultrasound)heart
Urinalysiskidneys
While taking
about 4–6 weeks in, then every 6–8 weeks — agree the exact schedule with your doctor
Lipid panel (HDL, LDL, triglycerides, ApoB)cholesterol, low estrogen
Liver panel (ALT, AST, GGT, bilirubin)liver
Complete blood count (hematocrit, hemoglobin)hematocrit
Kidney panel (creatinine, eGFR, cystatin C)kidneys, blood pressure
Estradiol (sensitive assay)low estrogen, libido
Prolactinprolactin, libido
Home blood-pressure logkidneys, blood pressure, heart
Urinalysiskidneys
After stopping
4–8 weeks after stopping (later after long-acting injections), then until values return to baseline
Lipid panel (HDL, LDL, triglycerides, ApoB)cholesterol, low estrogen
Liver panel (ALT, AST, GGT, bilirubin)liver
Complete blood count (hematocrit, hemoglobin)hematocrit
Kidney panel (creatinine, eGFR, cystatin C)kidneys, blood pressure
Testosterone (total, free), LH, FSH, SHBGnatural testosterone, libido
Semen analysisnot earlier than 3 months after stopping, then every 3 months until normalnatural testosterone
Every year
with regular or repeated use
ECGheart
Echocardiogram (heart ultrasound)heart
Which doctors can help
Sports physiciancoordinates everything
Cardiologistcholesterol, blood pressure, hematocrit, heart
Endocrinologistnatural testosterone, low estrogen, prolactin, libido
Dermatologistacne, hair loss
Gastroenterologist / hepatologistliver
Nephrologistkidneys
Psychotherapist / psychiatristmood
Urologistlibido
Gynecologistvirilization, natural testosterone, libido (women)
At home
- Home blood pressure: 2–3 times a week in the morning, keep a log
Get medical help at once if
- Yellow skin or eyes, dark urine, pale stools, intense itching, pain under the right ribs — see a doctor now; sudden severe abdominal pain with dizziness or fainting — call emergency services.
- Much less urine than usual, cola-colored urine, new swelling, flank pain — see a doctor now.
- Sudden severe headache, vision changes, numbness or weakness on one side, trouble speaking — call emergency services.
- Swelling, pain or redness in one leg; sudden shortness of breath or chest pain; sudden one-sided weakness or numbness, trouble speaking or seeing — seek urgent care.
- Chest pain or pressure, breathlessness on light effort, swollen ankles, fainting — seek urgent care.
- Losing control of anger, thoughts of harming yourself or others — stop and get help today.
- A new lump (including in the neck), trouble swallowing or persistent hoarseness, unexplained weight loss, or blood in stool or urine — see a doctor promptly.
- Deepening voice, new facial hair, clitoral enlargement — stop and see a doctor: changes can become permanent. (women)
In an emergency, call your local emergency number.
For women
Both strongly androgenic and progestogenic: virilization and menstrual disturbances are expected in women; voice and clitoral changes may be permanent. Must not be used in pregnancy: androgens can virilize a female fetus.
Myth & fact
Myth
“"The Clear" is a clean steroid.”
Fact
The name referred to escaping doping tests, not to safety. It was never tested in people, binds several hormone receptors and caused chromosome errors in cell studies.
Combinations
No specific combination notes for this substance yet. The stack check still adds up side effects that several substances share.
Sources
Death AK et al. Tetrahydrogestrinone is a potent androgen and progestin. J Clin Endocrinol Metab 2004 (opens in a new tab)Friedel A et al. Tetrahydrogestrinone is a potent but unselective binding steroid and affects glucocorticoid signalling in the liver. Toxicol Lett 2005 (opens in a new tab)Catlin DH et al. Tetrahydrogestrinone: discovery, synthesis, and detection in urine. Rapid Commun Mass Spectrom 2004 (opens in a new tab)
Check how Tetrahydrogestrinone combines with your stack
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