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testolactone Steroid Profile

Pharmaceutical Name: Testolactone
Chemical Structure: 17 alpha-oxa-D-homo-1,4-androstadiene-3,17-dione
Molecular Weight: 300.3968
Molecular Formula: C19 H24 O3
Melting Point: N/A
Active Life: approximately 24 hours
Anabolic/Androgenic Ratio: N/A

Similar to mesterolone, testolactone is an anabolic steroid that is primarily used for its ability to combat estrogen-related side effects and not the muscle-building properties of the compound. Like most drugs which feature "anti-estrogen" effects, testolactone was first manufactured and prescribed for the treatment of estrogen dependent breast cancer, as it is a first generation non-selective steroidal aromatase inhibitor. Testolactone is able to inhibit the aromatase enzyme noncompetitively and irreversibly, thereby limiting estrogen production in the body. However with the discovery and subsequent availability of more potent and effective drugs for this purpose, testolactone has seemingly been deemed obsolete for the purpose of battling breast cancer.

Despite the drug no longer being utilized for its originally intended purpose, testolactone still offers several unique advantages for steroid users. First, research has shown that the compound can effectively treat and prevent gynocomastia (1). This is seemingly accomplished by way of aromatase inhibition as opposed to the estrogen agonist/antagonist mechanism that tamoxifen citrate accomplished this effect with.

The second benefit that strength athletes, bodybuilders and other who make use of performance-enhancing drugs could experience by taking testolactone is the ability of the compound to help increase the natural testosterone production of users. This increase is prompted by several physiological mechanisms.

In several studies it has been demonstrated that not only is the level of testosterone increased in users significantly, but that this is likely caused by the ability of the compound to also increase the levels of androstenedione, leutenizing hormone and follicle stimulating hormone in the body (2,3). Obviously all of this would suggest that testolactone offers several advantages to those with suppressed natural testosterone production, with male steroid users coming off of anabolic steroids clearly being this group.

Returning to the aromatase inhibition action of testolactone, the effects of this drug are similar to those of other aromatase inhibitors. That is to say that testolactone can help to minimize aromatization and lowers the levels of circulating estradiol. However the level to which testolactone can accomplish this is somewhat clouded due to contradictory research. For example, one study indicated that administering one gram of testolactone to a group of healthy men for nine days resulted in only a twenty five percent decline in the level of circulating estradiol (4). However another study found that users taking one gram of the compound over only six days cut their estradiol levels in half (5). So while it can be concluded that testolactone will lower the level of circulating estadiol, there is no definitive answer as to exactly how effective it truly is. As for controlling aromatization, testolactone has been shown to reduce it by up to ninety five percent in some cases.

Use and Dosing of testolactone>

In terms of dosages needed to experience the results outlined above, for the most part it has been concluded that maximum estrogen suppression is achieved with 250 milligrams per day (6). However like most compounds some users may be able to achieve effective results with lesser dosages.

While testolactone has been shown to be an effective compound for the treatment and prevention of gynocomastia, the main benefit it can offer users is during post-cycle therapy. The ability to help increase the natural production of testosterone, as well as the precursors to testosterone, would undoubtedly serve a user well when he is attempting to re-start and raise his hormonal production to their regular levels.

Based on the available research it appears that the increases in hormonal production are achieved relatively rapidly. When used for post-cycle therapy, three to four weeks is seemingly adequate to achieve good results in the majority of users. However if one wished to run the compound for a lengthier period of time, there are no indications that long-term use is detrimental in any way.

Risks/Side Effects of testolactone

Similar to other drugs which limit the production and/or amount of circulating estrogen in the body, testolactone can negatively affect the health of the user. The most common side effects include a reduction in sex drive, a general lack of motivation and a negative impact on both HDL and LDL cholesterol, among others. For the most part however these side effects are relatively minor in the majority of users, especially compared to those of the currently available second and third generation drugs that are far more potent.

It should also be noted that although testolactone is technically an anabolic steroid, due to the compound not being able to bind to the androgen receptor and activate it (6), there should be no negative side effects related to the anabolic effects of the compound as there are none directly attributable to the drug.

From the available research there are no indications long-term use of testolactone is harmful in any way. However it should be noted that the research is extremely limited in this regard.


1. Zachmann M, Eiholzer U, Muritano M, Werder EA, Manella B. Treatment of pubertal gynaecomastia with testolactone. Acta Endocrinol Suppl (Copenh). 1986;279:218-26

2. Zumoff B, Miller LK, Strain GW. Reversal of the hypogonadotropic hypogonadism of obese men by administration of the aromatase inhibitor testolactone. Metabolism. 2003 Sep;52(9):1126-8

3. Dony JM, Smals AG, Rolland R, Fauser BC, Thomas CM. Effect of aromatase inhibition by delta 1-testolactone on basal and luteinizing hormone-releasing hormone-stimulated pituitary and gonadal hormonal function in oligospermic men. Fertil Steril. 1985 May;43(5):787-92

4. Smals AG, Dony JM, Smals AE et al. Aromatase inhibition by delta 1-testolactone does not relieve the gonadotropin-induced late steroidogenic block in normal men. J Clin Endocrinol Metab 1985 Jun;60(6):1127-31

5. Leinonen P, Bolton, NJ, Kontturi M, Vihko R. Rapid endocrine effects of tamoxifen and testolactone in prostatic carcinoma patients. Prostate 1982;3(6):589-97

6. Llewellyn, William, Anabolics 2004, 2003-4, Molecular Nutrition, p. 199

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