Evidence from Human Clinical Trials
TL;DR:
Clinical trial data shows that RAD140 decreases natural testosterone levels through suppression of the hypothalamic–pituitary–gonadal (HPG) axis. Despite its anabolic properties, it does not raise testosterone, and suppression has been observed even at therapeutic doses.
✅ Key Takeaways: Does RAD140 Increase or Decrease Testosterone?
- RAD140 does not increase testosterone — it mimics its effects by activating androgen receptors, but suppresses natural production.
- Clinical trials confirm suppression:
In the Phase I human study (NCT04116437), RAD140 led to dose-dependent suppression of testosterone, LH, and FSH. - Mechanism of suppression is consistent with other androgens:
RAD140 triggers negative feedback on the hypothalamic–pituitary–gonadal (HPG) axis, reducing GnRH, LH/FSH → testosterone drops. - Symptoms of suppression may include: low libido, fatigue, brain fog, testicular shrinkage, and poor recovery.
- Post Cycle Therapy (PCT) is often needed in research settings to restore hormonal balance—common agents include Enclomiphene and Tamoxifen (studied in other androgen-deprived contexts).
- Recovery is typically possible, especially with short cycles and proper recovery protocols—but may take weeks or months depending on individual response and dosage.
- There is no evidence that RAD140 increases total testosterone in any clinical setting.
🧪 What Clinical Trials Say About RAD140 and Testosterone Suppression
RAD140 (Testolone) is a selective androgen receptor modulator (SARM) investigated for androgen-receptor-positive cancers and muscle-wasting conditions. Its selective action targets muscle and bone, but like anabolic steroids, it can suppress endogenous testosterone.
Phase I Clinical Trial (NCT04116437)
Conducted by Radius Health, this trial evaluated RAD140 in patients with breast cancer. While the primary endpoint was safety and tolerability, hormonal assessments showed dose-dependent suppression of testosterone and gonadotropins in male participants.
🔬 Mechanism of Suppression – Clinically Supported
The suppressive action of RAD140 is explained through its agonistic binding to androgen receptors in muscle and other tissues. The body senses this activation and, via negative feedback on the HPG axis, reduces secretion of GnRH, LH, and FSH, which in turn lowers endogenous testosterone.
This is not hypothetical—clinical pharmacology data show that exogenous androgens, including SARMs, exert this effect as a class.
“Administration of selective androgen receptor modulators leads to suppression of the HPG axis, with corresponding decreases in serum testosterone.”
— Journal of Clinical Endocrinology & Metabolism, 2019;104(2):557–566
DOI: 10.1210/jc.2018-01927
Core understanding: What is RAD140?
📉 Summary of Clinical Trial Findings on Testosterone
Findings from RAD140 Human Trials:
| Endpoint | Observed Outcome |
|---|---|
| Testosterone Levels | Decreased across study duration (Phase I) |
| LH/FSH levels | Suppressed dose-dependently |
| Side effects | Included signs of androgen axis modulation |
| Dose range | 50 mg/day used in therapeutic settings |
📍Note: Although the primary trial focused on oncology patients, the mechanism of suppression is consistent with other SARMs studied in male populations.
⚠️ Why RAD140 Feels Like Testosterone… But Isn’t
Participants in observational and pilot studies often report increased energy, libido, and strength early in a cycle. However, these effects are due to androgen receptor activation, not an actual rise in serum testosterone.
Without testosterone lab monitoring, it’s easy to confuse androgenic effects with actual increases. In clinical studies, even with strong anabolic response, testosterone levels still decline.
✅ Clinical Implications for PCT (Post Cycle Therapy)
There is currently no officially approved post-cycle therapy protocol for RAD140 outside of research. However, SARMs like RAD140, due to their suppressive effect, may require intervention to restore hormonal balance.
In androgen-deprivation or SARM cessation contexts, agents like Enclomiphene or Tamoxifen are under investigation to restore LH/FSH levels.
“Clomiphene and Enclomiphene citrate stimulate gonadotropin release and restore testosterone in suppressed males.”
— Reproductive Biology and Endocrinology, 2020
While not part of the RAD140 clinical trial itself, this data is applicable by mechanism.
🔄 Testosterone Recovery Post RAD140 – Clinical Perspective
The duration and dose of RAD140 correlate with the depth and duration of suppression. Although long-term fertility and testosterone recovery outcomes have not yet been fully established in clinical literature for RAD140 specifically, data from other SARMs suggest:
- Recovery is likely after cessation, especially with PCT
- Younger males recover more quickly
- Extended cycles or stacking may delay recovery
A follow-up trial or post-market observational studies are needed to fully quantify testosterone restoration timelines after SARM discontinuation.
FAQ (Evidence-Based)
📉 Does RAD140 increase testosterone?
No. Clinical trials show it suppresses natural testosterone production via negative feedback on the HPG axis.
🧪 Is suppression proven in humans?
Yes. Phase I human trials (NCT04116437) showed measurable suppression of testosterone and gonadotropins.
💊 Is post-cycle therapy required?
While not officially prescribed, recovery agents (e.g., Enclomiphene) are used off-label in SARM cessation protocols due to known suppression patterns in clinical contexts.
🔁 Can testosterone recover post-RAD140?
Yes, especially with short cycles. But full recovery may take weeks to months and varies by individual.
Can you buy RAD140 in the UK?
Yes, it’s available from our SARMs research grade range.
Final Word: Follow the Clinical Data
RAD140 is not a testosterone booster. It’s a powerful androgen receptor agonist that can suppress your body’s testosterone even in therapeutic, clinically studied doses.