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Testosterone isobutyrate profile

Testosterone isobutyrate Background and History

Testosterone isobutyrate is an injectable esterified variant of the base testosterone hormone. It was first developed in the 1950s and was introduced for medical use under the brand name Agovirin. It contained testosterone isobutyrate at a concentration of 100mg/mL in oil.

Testosterone isobutyrate profile
Testosterone isobutyrate profile

Although initially popular, it eventually became overshadowed by other testosterone esters like cypionate and enanthate. Agovirin was discontinued in the 1980s but testosterone isobutyrate remains available today in various underground forms.

Chemical Structure

Testosterone isobutyrate is created by attaching an isobutyrate ester to the 17-beta hydroxyl group of the testosterone molecule. This esterification makes the steroid more fat soluble and extends its release time in the body after an intramuscular injection. The isobutyrate ester has a duration of about 2 weeks.

Dosages and Cycles

Typical dosing of testosterone isobutyrate is in the range of 300-500mg per week. It is only administered via intramuscular injections due to the ester attachment. 8-12 week cycle lengths are common, often stacked with other anabolic steroids like nandrolone decanoate or boldenone undecylenate. Shorter cycles are also possible but may require more frequent injections.

Effects and Benefits

The effects of testosterone isobutyrate essentially mimic those of natural testosterone itself. It exhibits strong anabolic and androgenic effects that stimulate muscle growth, strength gains, fat loss, and masculinization. The isobutyrate ester simply extends the release and activity period of the testosterone.

Compared to shorter unesterified testosterone preparations, testosterone isobutyrate offers more stable blood hormone levels but slower onset of effects. The tradeoff makes it better suited for longer cycles. The benefits sought are increased muscle mass, strength, endurance and improved body composition.

Side Effects and Health Risks

The side effects associated with testosterone isobutyrate match the potential risks and adverse reactions common to all anabolic steroids. These include:


      • Androgenic effects like prostate issues, baldness and body hair growth

      • Estrogenic effects like gynecomastia, water retention and high blood pressure

      • HPTA suppression

      • Cardiovascular strain

      • Liver toxicity

      • Acne and oily skin

      • Aggression or mood changes

    Proper precautions should be taken to minimize health risks. Post cycle therapy is important for hormonal recovery after use.

    Legal Status

    Testosterone, in all its forms, is designated as a DEA Schedule III controlled substance in the United States. It is illegal to possess or use testosterone isobutyrate without a valid prescription. Distribution or manufacturing also violates federal law. Despite regulatory controls, testosterone isobutyrate remains available through underground markets and foreign pharmacies. But buyers assume legal risk for importing or using the product.

    In summary, testosterone isobutyrate is a long-acting injectable testosterone ester with effects similar to natural testosterone. Although an effective anabolic steroid, its illicit status necessitates care and discretion with obtaining and administering it. As with all substances, responsible and informed use is imperative.


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