All Hail King Tren

TL:DR lack of human data forces some guesswork. Tren is highly anabolic, and has been shown to increase muscle size. Can cause mood swings, have a progesterone impact, and will impact cardiovascular health. Oddly, seems to increase attraction to Thai and Filipino ladyboys.

Tren was released for human consumption as trenbolone hexahydrobenzylcarbonate, with a big, throbbing & veiny long ester, and then ‘voluntarily withdrawn’ from the market in the 90s. Like we saw in DNP, a compound that is easily abused may be banned from the FDA in the US, which ultimately leads to it being withdrawn from the prescription market. It was anecdotally highly beneficial in its limited use case but unfortunately the clinical trial results have been more or less suppressed, and are written in some kind of code (french). Accordingly, I’m relying on clinical data from animals and inferences from broscience. I’m also speaking generally about tren and its esters (acetate, enanthate, undecanoate), and while there are some differences in effects this article is broadly applicable.

What makes Tren king is its versatility - give the high binding affinity and anabolic rating 5 times that of test , it offers advantage to cycles that look to preserve or add mass. It’s also lipolytic: Tren reduces fat while increasing muscle while otherwise at maintenance.

Tren binds to androgen receptors with 3 times the affinity of test. It is highly virilizing, inhibits spermiogenesis, and is more androgenic than test (interestingly, the research I’m citing here makes a claim that androgenicity and virilization seem to run parallel and that would make sense when we think of other highly androgenic and highly virilizing compounds, as well as the opposite, but I digress). Despite the high androgenic rating of 500 (test is the baseline of 100, making tren 5 times more androgenic), there is evidence that tren does not act as androgenic as the rating would imply, given research findings that tren does not have the same impact in organs as test:

17-TBOH (tren) exerts less pronounced effects than testosterone in androgen-sensitive tissues… Despite its inability to undergo 5(alpha) reduction, 17-TBOH remains highly anabolic.

This is demonstrated in Rat Study 2 below, and is due to tren not having as significant effect on tissue that express 5a reductase enzyme. This enzyme is what metabolizes testosterone into DHT, which has a strong binding affinity in areas such as the prostate which causes the undesirable side effect of tissue enlargement. Tren has either limited or no effect.

Medical Trials

Rat study 1: tren increased satellite cells (the precursor to skeletal muscle) by 178% compared compared to the neutered group. Oddly tren did not increase the number of myonuclei found in muscle (this generally happens before hypertrophy can occur), and myostatin was increased by 169% when compared to the neutered group but was lower than the unneutered control.

Rat study 2: dose dependent relation to fat loss is demonstrated, as well as improved bone density. At the lowest of doses, the neutered group did not increase prostate mass or hemoglobin, while improving skeletal muscle mass and lowered visceral fat. Researchers conclude that low dose tren only (without a test base) has its advantages over supraphysiological test and is an option for hormone replacement therapy.

Human studies are not really available: we are unaware of any paper that has reported the effects of 17-TBOH administration on the growth of androgen-sensitive tissues in humans. Given that rats are not a great analog for humans, especially where it comes to myonuclei, it’s not possible to make conclusive statements from the two rat studies. Or, for that matter, studies done in cattle or other mammals.

Side Effects - Actual

Mood swings: there are some undeniable effects of tren (beside getting swole) and a couple that I think we should be skeptical of. The first is the anecdotal evidence of its impact on mood which will vary. It’s not that it puts you in a bad mood per se, as it does have positive effects to the feeling of well-being that most PEDs do, but you might over-react to an unforeseen event. My personal experience is that trensomnia exasperates this side effect, and accordingly I recommend using sleep aids if you have tren in your cycle. I personally prefer CBD which is well tolerated and effective without straining kidneys, but /r/nootropics can recommend others if this is not suitable or available.

Progesterone: reliable data on tren and its relationship with progesterone receptors is lacking, however tren belongs to the nandrolone group of aas, which we know binds to the progesterone receptor with about 22% the affinity of progesterone. Ordinarily, men have very low levels of both prolactin (0.2ng/ml or less) and progesterone (1ng/ml or less). Even a small real increase in either, and there is a relationship between the two, will cause issues - specifically the growth of breasts. Nice. Prolactin and progesterone are both suppressed using cabergoline. B6 is also likely effective. Have either on hand during your tren cycle.

Cardiovascular health: Nandrolone, and tren which belongs in the same AAS family, put cardiac health is at risk. I’m using nandrolone as the proxy for tren, given lack of cardiovascular studies and the similarity in the compounds. Both will cause cardiac hypertrophy and result in poor LDL markers:

We found that 6 weeks of nandrolone treatment with or without accompanying physical training increased oxidative stress damage markers, unfavorable lipid profile, cardiac hypertrophy, fibrosis, and cardiac and coronary vessel proliferation in rats.

Oddly, this study demonstrated that nandrolone + cardio exercise (enforced swimming) actually worsened health compared to nandrolone + sedentary. It’s possible that the added stress of the type of exercise, which involves swimming until the rat starts to drown, had something to do with this and we should discount the fact that this study shows cardio worsened cardiac health. Either way, given that cardio was not shown to improve cardiac health in either of the nandrolone groups, diet then becomes the main variable that can the user can control to reduce impact to heart health and cholesterol levels.

On a positive note, tren is ‘relatively non-estrogenic’ and may have anti-estrogen effects in humans. It does possess an estrogen receptor binding efficiency of 20% of that of e2 which is not a problem as tren does not aromatize - there’s no conversion to DHT or e2. The implication of this is important later on in this article as it may support running tren only cycles: because tren binds to the estrogen receptor it may fill some of the role that e2 binding would ordinarily play.

Side Effects - Bro-science

There’s some broscience that tren is highly toxic to kidneys and/or liver and while tren is indeed metabolized in the liver, toxicity is low due to being administered intramuscularly (as opposed to orally or otherwise). I would not be overly concerned about this side effect unless running very high doses.

And on the topic of DHT - tren is reportedly devastating to hairlines, apparently due to its high androgenicity. But this doesn’t make sense from what we know of this compound - with no aromatisation comes no increase in DHT. No DHT means no acceleration of alopecia if predisposed:

In certain tissues, such as the prostate or in the hair follicles, testosterone is converted to dihydrotestosterone (DHT) by 5 alpha-reductase (5AR)... A critical role for DHT in hair growth can be seen in the case study of men with Imperato-McGinley syndrome. This condition results from a mutation in the gene for type II 5AR that prevents the expression of the enzyme. As a consequence, men with this condition never become bald.

My speculation is that that tren is not a contributor to hair loss, unless paired with a TRT or higher doses of test (say, 200mg or more every week). Given that tren is in the nandrolone group of aas, and that deca (also in this group) is ‘hair friendly’, I hold that this is more likely broscience than fact. That said, if you know better or have a link showing that tren / DHN does impact scalp androgen receptors, or the high binding affinity of tren affects scalp receptors in a novel way, or has some other action (such as displacing DHT ligands which causes a short term impact on hair) please share it with the bromunity - I’m happy to be wrong and post an update saying as much.

Sacred Cow: Tren must be paired with test

In multiple studies, researchers claim that tren is a potential candidate for hormone replacement therapy. One conclusion I found was especially poignant (paraphrased):

Tren prevents the alterations in body composition associated with losing ones testicles to the same extent as supraphysiological testosterone. Specifically, tren and supraphysiologic test produced equally myotrophic responses in both intact and de-balled animals, Tren partially prevented induced bone loss to roughly the same extent as supraphysiological test, and at equal doses, tren was somewhat more lipolytic (i.e. fat reducing) than test in visceral fat.

When you couple this conclusion with the lack of androgenic effect in the prostate, the binding to estrogen receptors, and the dose-gains relationship that rats shows on tren only cycles, this compound could theoretically be ran by itself. Tren will, however, result in shutdown via (presumably) HPTA feedback loop, leaving the individual in a low test state similar to a SARM or oral AAS only cycle, and would require PCT.


I’ve advanced two controversial ideas in this post, the first about tren not having an impact on hair loss and the second about tren only cycles being viable. It’s not my intention to be deliberately aggressive with these ideas for the sake of fake internet points, but rather the PEDsR mission is to learn, be curious, and question broscience wherever it is productive to do so. The one fact that cannot be disputed about tren is that with an anabolic rating of 500 it is incredibly effective at building and maintaining muscle. Be in a good place, mentally, before you run it.