Teslac — testolactone

Testolactone is a first generation non-selective steroidal aromatase inhibitor, used clinically to treat estrogen-dependent breast cancer. Its exact mode of action is unknown, but it is believed to inhibit the aromatase enzyme in a noncompetitive and irreversible manner. If so, this would be an activity that is very similar to that of Lentaron and its derivatives normally possess. This is likely where testolactone got its name, which may be short for testosterone. For example, one study conducted in 1985 showed that 1,000 mg of testolactone per day given to nine normal men for a period of ten days suppressed serum estradiol levels by 25% . Another using the same 1,000 mg dose noted a 50% reduction after six days of use . These numbers are lower than what would be expected of the newer third-generation agents given the substantial estrogen suppression figures they have produced during clinical trials with women.

Brand name Teslac, Testolactone

Testolactone History

Testolactone was first approved as a prescription drug by the FDA back in 1970. It was an early anti-estrogenic drug, exhibiting a moderately pronounced effect but failing to reach levels of high clinical success. As other more effective medications began to surface for the treatment of breast cancer, testolactone would not see the success its developers likely planned for it. It would see production in a small number of countries outside the U.S., most notably Brazil, Germany, and Chile. It has since been discontinued in all countries but the U.S., where the Teslac brand is still available.

How is Testolactone Supplied

Testolactone is most commonly supplied in tablets of 50 mg.

Structural Characteristics of Testolactone

Testolactone is classified as a steroidal noncompetitive irreversible steroidal aromatase inhibitor. It has the chemical designation 13-hydroxy-3-oxo-13,17-secoandrosta-1,4-dien- 17-oic acid [dgr ]-lactone.

Testolactone Side Effects

Common side effects associated with the use of an aromatase inhibitor include hot flashes, joint pain, weakness, fatigue, mood changes, depression, high blood pressure, swelling of the arms/legs, and headache. In 1999, the FDA officially added malaise to the list of possible side effects from this drug, reflecting something bodybuilders had noticed for some time: low estrogen levels can lead to lethargy, as this sex hormone plays an important role in the functioning of the central nervous system. Aromatase inhibitors may also decrease bone mineral density, which may lead to osteoporosis and an increase in fractures in susceptible patients. Some individuals may also respond to the medication with gastrointestinal side effects including nausea and vomiting. Aromatase inhibitors can harm the development of an unborn fetus, and should never be taken or handled during pregnancy. When taken by men (as an off-label use) to reduce estrogenicity during prolonged periods of steroid treatment, aromatase inhibitors may increase cardiovascular disease (CVD) risk by retarding some beneficial properties of estrogen on cholesterol values. Studies have demonstrated that when an aromatizable steroid such as testosterone enanthate is taken in conjunction with testolactone, suppression of HDL (good) cholesterol levels becomes significantly more pronounced. Since the estrogen receptor agonist/antagonist Nolvadex generally does not display the same anti-estrogenic (negative) effect on cholesterol values, it is usually favored over aromatase inhibitors for estrogen maintenance by male bodybuilders and athletes concerned with cardiovascular health.

Testolactone Administration

Testolactone is FDA approved as adjunctive therapy in the palliative treatment of advanced or disseminated breast cancer in postmenopausal women when hormonal therapy is indicated. It may also be used in women who were diagnosed as having had disseminated breast carcinoma when premenopausal, in whom ovarian function has been subsequently terminated. The recommended dosage is 250 mg taken 4 times per day.

When used (offlabel) for estrogen suppression in male steroid users, a dosage of 250 mg (five tablets) is usually taken per day.

Testolactone Availability

Testolactone is no longer commonly used in clinical medicine, and consequently is not manufactured on a large sale globally. Presently a small number of testolactone preparations still exist, but are not commonly diverted for sale on the black market given the very low demand for the drug in this population.

Bodybuilders reference

Teslac is used as an anti-estrogen. Instead of acting as an estrogen antagonist (competing for estrogen receptor-sites), Teslac prevents the aromatization of androgens into estrogens by inhibiting the aromatase enzyme. Obviously this prevents or minimizes the negative effects of estrogen such as gyno, water retention, and female pattern fat deposits. Teslac is unique in that it is reputed to cause permanent irreversible suppression of estrogen production in males.

Technically speaking, Teslac is an oral androgenic steroid related to testosterone. However, it has only very low androgenic and no anabolic effect. Medical use of Teslac is for treatment of breast carcinoma in women. For male athletes, it is probably the best anti-estrogen available, and it causes an increase in natural (endogenous) testosterone production. Teslac elevates natural testosterone production by influencing the HYPOTHALAMUS to stimulate the PITUITARY to release more gonadotropin. This in turn simulates the testes Leydig cells to produce more testosterone at a significantly increased level (Comparable to HCG). Unlike HCG, Teslac takes several days to cause this effect. So administration over a prolonged period (several days) clinically considered necessary (under a doctors care). For this reason Teslac does "create" an improved anabolic/androgenic environment. Even so-called natural (like lifting tons of weight and drinking protein powders is natural) bodybuilders have employed benefits form this drug.

*Plasma calcium elevation has been during administration of Teslac.

Manufacturer inserts suggest a dosage of 250-1000mg daily. However, this is not reported as necessary for estrogen suppression. Normally 200-300mg daily divided into 2-3 doses was reported as quite effective. Some reported 100-mg of the injection form version was even more effective. Due to the high price of Teslac, many have stacked it with PROVIRON: Teslac-100-mg daily and Proviron 50-mg daily. Women users reported excellent hardening effects with few, if any, side effects such as virilization.

Side effects are very rare but could include nausea, vomiting, tongue infection, swelling and pain in arms and legs, prickling sensation and high blood pressure, as well as loss of appetite. As mentioned earlier, side effects were rare but women often skipped menstruation during use.

This is probably rated as the most effective overall anti-estrogen available whether during or post cycle as well as for pre-contest overall hardening effects.

Anabolic Steroid Guide reference

Teslac belongs to the group of sex hormones and from a biochemical perspective, is a relative of the testosterones. Although this catego-rizes it as an androgenic steroid, from a technical point of view it is neither an androgenic nor an anabolic steroid. Teslac is very similar to the structure of androgenic steroids but it has only a very low androgenic and no anabolic effect. In school medicine this compound is used in the treatment of advanced mammary carcinomas in women. Before you discard Teslac as a completely useless drug and stop reading we want to tell you that Teslac does have his justified application in bodybuilding. Two reasons speak for an intake of Teslac: First, it is the most effective antiestrogen and second, it causes a distinct increase of the endogenic (body's own) testosterone production. Teslac is unique in its effectiveness as an antiestrogen. Like Proviron, it prevents the aromatizing process of the steroids from the basis. Thus, Teslac prevents almost completely the introduction of more estrogens into the blood and subsequent bonding with the estrogen receptors. Athletes who want to be absolutely certain combine Teslac with Proviron 50 mg/day and obtain a complete sup-pression of the estrogens. What makes Teslac different from Proviron, however, and so desirable is the characteristic that it can lead to an irreversible and permanent suppression of the estrogens in male ath-letes. Studies, in the meantime, have proven that Teslac makes male athletes resistant to an aromatization of steroids over a prolonged period. A water retention caused by the estrogens and gynecomastia is thus avoided in the long term. Another advantage of Teslac is that it directly influences the hypothalamus and upon its "signal" the hypophysis releases more gonadotropine, leading to a significant increase of the endogenic testosterone level. The strength of the testosterone-stimulating effect of Teslac can be compared with the one of HCG (see also HCG). Unlike HCG which after only a few-hours results in an elevated plasmatestosterone level, Teslac does require a longer initial period. Thus a regular intake over several days is a preliminary. Although we have initially mentioned that Teslac does not have an anabolic effect, based on the increased testosterone level, a gain in muscles and strength can occur. This could lead to androgenically linked side effects but they are very unlikely.

Side effects from Teslac are very rare. Since this compound, above all, was developed for women, it was extremely important to exclude the androgenic effect component as much as possible. This was successfully accomplished so that females very rarely experience masculinizing symptoms such as, for example, increased growth of body hair or deep voice. Possible side effects from Teslac are given on the package insert by the German manufacturer, Bristol Arzneimittel GmbH, for the remedy Fludestrin: "cutaneous eruptions (maculopapular erythema), high blood pressure, sensations such as itching and pricking (paresthesia), pain in the arms and legs and swelling, tongue infection, loss of appetite, nausea and vomiting." These side effects, as already mentioned, are extremely rare. The plasma calcium level of athletes should, however, be checked since Teslac could lead to hypercalcemia (increased calcium level). Perhaps the greatest negative side effect of Teslac is its high price. A package of fifty 50 mg tablets costs about $200 on the black market. Every single tablet thus costs $4. The recommended daily dose of 10-20 tablets that is 500-1000 mg/day! Usually 4-5 tablets daily (200-250 mg/day) are sufficient. However even such a dosage will discourage most athletes because of the high cost. An alternative would be to limit the intake of Teslac to two tablets per day and to supplement them with the similarly effective Proviron (50 mg/ day).

Newbie Research Guide reference

Testolactone is a steroidal aromatase inhibitor, structurally similar to testosterone. It was first made available in the 1960’s, at a time when conventional breast cancer therapies included androgenic steroids. It was developed in an effort to produce an effective agent for breast cancer that was devoid of virilizing activi- ty, and to that end testolactone fits well; it is completely devoid of androgenic activity (at high doses its activity is in fact antiandrogenic). It is quite interesting to note that it was not discovered to act by inhibiting aromatase until 1975. By this time testolactone had already fallen out of favor with the medical community, due in part to its low rate or response, as well as the utilization of stronger agents such as aminoglutethimide.

Although testolactone may still be available, it is a poor choice for the athlete. There are just too many drawbacks to its use. It is expensive, and studies show that 4 tablets (1000mg) are typically needed each day for a sufficient level of estrogen suppression. It may also be an antagonist of the androgen receptor to some extent, certainly an unwanted effect for the steroid user. Being a testosterone derivative it is additionally a controlled substance in the Unites States. Though it does admittedly work as a weak aromatase inhibitor, the hassle of obtaining it combined with the obvious greater effectiveness of other agents such as tamoxifen make it a rare find these days.


Wlliam Llewellyn (2011) - Anabolics
L. Rea (2002) - Chemical Muscle Enhancement Bodybuilders Desk Reference
Anabolic Steroid Guide
Newbies Research Guide reference

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