Metribolone
Active ingredient: Methyltrienolone (Metribolone, R1881). Orally active Trenbolone and in the laboratory the standard ligand for the androgen receptor, to which it binds more tightly than any other tested steroid. Never studied on humans. It also binds the progesterone receptor.
Auch bekannt als: Metribolone, R1881, Methyltrienolon, Oral Tren, M-Tren, Methyltrienolone
What it is
Methyltrienolone, listed in research as R1881, is 17β-hydroxy-17α-methyl-estra-4,9,11-trien-3-one. The molecular formula is C₁₉H₂₄O₂. It is Trenbolone with an additional methyl group at C17, so the same relationship as between Nandrolone and Norethandrolone: the 19-nor framework that carries the double bonds at 4, 9 and 11, plus the attachment that makes the substance swallowable.
It was never a medicine. This substance made its real career in the laboratory: it is the standard ligand with which androgen receptors are made visible in tissue samples. That is the reason why it is available for sale at all and the reason why it is traded in the scene as a research chemical.
How it works
Why it became the reference ligand
In the 1970s, a method was developed to find the most specific labeled ligand possible for each class of steroid receptors. A crude extract was prepared from target organs and over 700 molecules were measured to see how well they displace the labeled ligand from its binding; For 81 of these, it was evaluated which additions to the steroid framework change affinity and specificity and how. Methyltrienolone emerged from this process as the ligand for the androgen receptor.
How strongly it binds is shown by a later series of displacements on skeletal muscle and prostate: Methyltrienolone was the one there most effective competitors of all, before Nandrolone, Metenolone and testosterone. The statement that this substance binds the androgen receptor more tightly than any other common steroid is one of the few potency statements in this category that have actually been measured.
And not as specific as the name suggests
Of all things, the specificity is limited when it comes to the reference ligand for the androgen receptor. Methyltrienolone binds with high affinity to protein from human prostate tissue; it binds the androgen receptor of the rat prostate and the progesterone receptor in the rabbit uterus. If you check which other steroids compete for binding sites in human prostate tissue, the pattern is more similar to that of the progesterone receptor than to that of the androgen receptor; These progesterone receptor-like binding sites are located in the connective tissue of the prostate and not in the glandular epithelium.
For the user, this explains the widespread observation of a gestagen effect. In the case of this substance, it is not only derived from the 19-nor structure, but has also been demonstrated in a binding experiment, albeit on animal tissue and human prostate tissue instead of at an end point. For laboratory practice, this means that a finding with this ligand does not solely reflect the androgen receptor without further precautions.
No flavoring
The three double bonds in the framework undergo a transformation through the aromatase impossible. There is no estradiol produced, there is no estrogen-related water retention, and a aromatase inhibitors has nothing to inhibit. Anyone who uses the substance alone has low androgen and estrogen levels at the same time, see Estrogen.
What the studies show
There is nothing to humans. No controlled study, no observational series, no dose determination, no measurement of strength, muscle mass or side effects, and no approval in any country. The search was for the free name, the research identifier R1881 and for use on humans; what comes back is receptor research.
This puts this material in a class of its own. Most steroids in this category lack efficacy studies, but at least there are case reports or clinical history. There is neither here: What is said about Metribolone comes entirely from binding data and user reports.
The only study on the liver question
Metribolone is considered one of the most liver-toxic steroids available. A case report that would support this could not be found. What was found is a French paper from 1970 entitled “Absence of hepatotoxic signs in pigs given high doses of methyltrienolone in the diet.”
There is no abstract available for this work; There is therefore nothing here other than what the title suggests. It is not suitable as an all-clear: pigs are not people, food is not a tablet, and a missing finding in a single old test is not proof of safety. What it shows is that the attribution “extremely liver toxic” for this substance is not based on any measurement. The suspicion remains justified because the methyl group at C17 is the same as at Methandienone and Methasterone, and in these cases the bile buildup is well documented. But it remains a conclusion based on the construction method.
For the substance class as a whole, a review article describes short-term administration increases in strength of around 5 to 20 percent of the initial value and 2 to 5 kg of body weight, as well as increased blood pressure, reduced HDL cholesterol and a disruption in one's own hormone production, which can last months after discontinuation. Where Metribolone lies within is not determined; its bond strength suggests the upper end.
Dosage
- There is no dose to rely on. Not in the sense of “not tested on humans”, but in the sense of: This substance was never a medicine, there is no package leaflet, no study dose and no clinical experience. The circulating fractions of a milligram are common practice.
- The high bond strength is the reason for the low margin. A substance that binds the receptor more tightly than any other common steroid, achieves its effect with a correspondingly small amount, and therefore the effective and excessive doses are close together. A measurement in the range of fractions of a milligram is not possible with budgetary resources.
- What is sold as a research chemical has not been tested. Purity and content are not subject to control, and for a substance where the dosage is determined by a factor of ten, this is the single largest uncertainty.
- Not next to a second oral steroid. Two 17-alpha-alkylated preparations attack the same place in the liver, and this substance has no information about what it does there alone.
- An aromatase inhibitor has no target here. Without aromatization there is nothing to inhibit; it just lowers estradiol from other sources in the stack.
- Initial values before the first dose. transaminases, Bilirubin, alkaline phosphatase, blood pressure and lipid profile. For a substance without any safety data, your own measurement is the only information available.
Side effects
Your own axis
What happens: An supplied androgen drives the HPTA axis down, LH and FSH fall, your own production comes to a standstill. With a substance that binds the receptor more tightly than any other steroid tested, a particularly complete suppression can be expected.
What it depends on: Of dose and duration. A measurement of LH, FSH and testosterone under Metribolone could not be found; For this class of substances, the disorder can persist for months after discontinuation. What follows from this is: The expectation is based on bond strength rather than measurement, and it goes in the unfavorable direction. What you can do: Keep the use short, plan the exit in advance, determine testosterone and LH before starting and after stopping. For the restart HCG and Clomiphene the established remedies, both requiring a prescription.
The progestin side
What happens: In addition to the androgen receptor, Metribolone also binds the progesterone receptor, and in human prostate tissue its binding pattern is more similar to that of the progesterone receptor. Partial progestin action may affect libido and erection more than testosterone or estradiol levels suggest, and may contribute to the growth of mammary tissue without the involvement of estradiol.
What it depends on: Of dose and duration. What is measured is the bond, not the effect on people. What follows from this is: Anyone who expects the progestin side correctly interprets a loss of libido with normal estradiol instead of continuing to use the aromatase inhibitor. An aromatase inhibitor doesn't work here anyway. What you can do: If there is a feeling of tension behind the nipple or a lack of recovery, testosterone, estradiol and Prolactin let it be determined together before a cause is assumed.
Liver
What happens: In other oral steroids, the methyl group at C17 interferes with the removal of bile salts from the liver cell; A build-up of bile occurs with jaundice and itching with little cell death. This has not been shown for metribolone itself: there is no case report, and the only study found found no hepatotoxic signs in pigs given high feed doses.
What it depends on: Presumably due to the dose and duration, as with related substances. What follows from this is: The data here is not reassuring, but rather empty, and that is something different. However, for a substance that works in fractions of a milligram, the absolute amount that passes through the liver is very small, and this differs from substances that are taken in double-digit milligram amounts. What you can do: transaminases, Bilirubin and alkaline phosphatase before the start and after two weeks, because there is no empirical value that could be used as a guide. If yellowing, dark urine or itching occurs, discontinue use immediately.
Blood lipids and blood pressure
What happens: For the substance class, a review article mentions increased blood pressure and reduced blood pressure HDL cholesterol together with its sub-factions as the significant risk changes. Since Metribolone does not aromatize, estradiol, which has a beneficial effect on blood lipids in men, is missing.
What it depends on: From the oral route and from the dose. There are no figures specifically for Metribolone. What follows from this is: The effect is not noticeable, only measurable, and with a substance without any safety data, your own measurement is the only feedback you get. What you can do: Lipid profile and blood pressure before the start and after two to four weeks, see Cardiovascular risks associated with AAS.
Classification
Metribolone is a special case among the substances in this category: its effectiveness is better documented than almost all others, and less is known about its effects and tolerability in humans than about any other. In the displacement series it was the most effective competitor at the androgen receptor, and it emerged as a standard ligand from a process involving over 700 molecules tested. It has never been studied in humans because it was never intended to be a drug.
The most interesting finding contradicts its reputation as the most specific androgen ligand. It also binds the progesterone receptor, and in human prostate tissue its binding behaves more like that of a progestogen than that of an androgen. What is described in the scene as a gestagen side effect has a measured basis, and it comes from the work that questions the substance as a tool.
However, the widespread warning about extreme liver toxicity has not been proven. There is no case report, and the only study found on the question found nothing in pigs. That doesn't exonerate the substance, it just shifts the reasoning: The concern arises from the design it shares with the well-documented oral steroids, and not from observations on itself.
What would decide the matter is the very first stage with this substance: a measurement of liver values, blood lipids and hormones in users over two to four weeks. There is not even a case series on Metribolone, and therefore there is no basis on which the benefits and harms could be weighed against each other. Anyone who takes it is conducting a self-experiment for which there is no template.
Sources
- Ojasoo T, Raynaud JP. Unique steroid congeners for receptor studies. Cancer Res. 1978. PubMed
- Saartok T, Dahlberg E, Gustafsson JA. Relative binding affinity of anabolic-androgenic steroids: comparison of the binding to the androgen receptors in skeletal muscle and in prostate, as well as to sex hormone-binding globulin. Endocrinology. 1984. PubMed
- Cowan RA, Cowan SK, Grant JK. Binding of methyltrienolone (R1881) to a progesterone receptor-like component of human prostatic cytosol. J Endocrinol. 1977. PubMed
- Szumowski P, Grandadam A. Absence of hepatotoxic symptoms in swine receiving high doses of methyltrienolone in their diet. C R Seances Soc Biol Fil. 1970. PubMed
- Hartgens F, Kuipers H. Effects of androgenic-anabolic steroids in athletes. Sports Med. 2004. PubMed
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