Anastrazole
By Dr. Alexander Reynolds, MD, CSCS – Sports Medicine Specialist & Performance Consultant
As a sports medicine physician and performance consultant who works closely with elite bodybuilders, I am frequently asked about pharmaceutical compounds used during anabolic-androgenic steroid (AAS) cycles. One of the most commonly referenced medications is anastrozole, marketed under the brand name Arimidex®. While I do not advocate or prescribe anabolic steroids, given their legal, ethical, and medical complexities, it is my professional responsibility to provide accurate, science-based information to athletes who may choose to use such compounds. This article will explore anastrozole in depth: its history, mechanism of action, benefits, risks, and appropriate use within the context of bodybuilding cycles. I will also address nutrition, cycle integration, and clinical monitoring from both a medical and performance training standpoint.
1. Historical Background of Anastrozole
Anastrozole was first developed in the late 1980s by Zeneca Pharmaceuticals (now AstraZeneca) as a third-generation aromatase inhibitor (AI). It received FDA approval in 1995 for the treatment of hormone receptor-positive breast cancer in postmenopausal women. Its primary function is to suppress the conversion of androgens (like testosterone) into estrogen via inhibition of the aromatase enzyme.
In the oncology setting, anastrozole is highly effective because estrogen can fuel the growth of certain breast cancers. By lowering systemic estrogen levels by up to 80%, it helps slow or reverse tumor progression. Over time, its potent anti-estrogenic properties attracted attention beyond oncology—particularly in the world of competitive bodybuilding and strength athletics.
Bodybuilders began adopting anastrozole in the late 1990s and early 2000s as a tool to manage estrogenic side effects during steroid cycles. Its precision, potency, and relatively predictable pharmacokinetics made it a preferred choice over earlier AIs like aminoglutethimide or even non-prescription “natural” estrogen blockers.
2. Positive Effects of Anastrozole on the Body
Anastrozole’s primary benefit lies in its ability to modulate estrogen levels. In the context of bodybuilding, elevated estrogen during a testosterone-based cycle can lead to several undesirable outcomes. Here’s how anastrozole helps:
A. Prevention of Gynecomastia
One of the most feared side effects of high-dose testosterone or other aromatizable steroids (e.g., dianabol, testosterone enanthate) is gynecomastia—the development of breast tissue in males. This occurs when excess testosterone is converted to estradiol (E2), which then binds to estrogen receptors in breast tissue. Anastrozole effectively reduces E2 levels, thereby preventing or halting the onset of gynecomastia.
B. Reduction in Water Retention
High estrogen promotes sodium and water retention, leading to a “puffy” or “soft” appearance—undesirable during contest preparation. By lowering estrogen, anastrozole helps achieve a tighter, more defined, and vascular look, enhancing muscle separation and striations.
C. Improved Lipid Profile (Indirectly)
While anastrozole itself does not directly improve cholesterol, high estrogen levels during a cycle can negatively impact HDL (“good” cholesterol). By managing estrogen, anastrozole may help mitigate some of the lipid disturbances caused by AAS, though this benefit is modest and must be balanced with cardiovascular monitoring.
D. Enhanced Testosterone Efficacy
When estrogen is too high, negative feedback on the hypothalamic-pituitary-gonadal (HPG) axis increases, potentially blunting endogenous testosterone production. While this is less relevant during exogenous steroid use, maintaining optimal E2:T ratios can improve overall hormonal balance and perceived well-being.
3. Negative Side Effects and Medical Risks
Despite its benefits, anastrozole is not without significant risks—especially when used inappropriately. As a physician, I emphasize that “optimal” does not mean “safe” when it comes to estrogen suppression.
A. Over-Suppression of Estrogen
The most common mistake among bodybuilders is using too high a dose or using anastrozole too frequently. Estrogen is essential for:
Joint lubrication and connective tissue health
Bone mineral density
Cognitive function
Cardiovascular protection
Libido and erectile function (in some individuals)
Over-suppression can lead to:
Joint pain and stiffness (a frequent complaint among AI users)
Tendinopathy and increased injury risk due to reduced collagen synthesis
Mood disturbances, including depression and irritability
Insomnia and fatigue
Loss of libido (paradoxically, despite high androgens)
Accelerated bone loss (increasing long-term osteoporosis risk)
B. Cardiovascular Concerns
While lowering estrogen may reduce water retention, it can also negatively affect endothelial function and lipid metabolism. Studies show AI use is associated with increased LDL and decreased HDL cholesterol, raising long-term cardiovascular risk—especially in individuals already using hepatotoxic compounds or trenbolone.
C. Impact on Recovery and Performance
Estrogen plays a role in muscle recovery and satellite cell activity. Excessive suppression may impair muscle repair and hypertrophy over time, counteracting the very gains athletes seek.
D. Liver Stress
Anastrozole is metabolized by the liver (via CYP3A4/5). While not as hepatotoxic as oral steroids, chronic use—especially when stacked with other liver-metabolized compounds—can contribute to hepatic strain. Regular liver enzyme monitoring (ALT, AST, GGT) is essential.
4. Why Is Anastrozole Sought After by Bodybuilders?
Anastrozole’s popularity stems from several key advantages:
High potency: Effective at very low doses (typically 0.25–1 mg every 3–7 days).
Predictable half-life (~40 hours), allowing for steady-state control.
Oral bioavailability: Easy to administer without injections.
Rapid onset: Reduces estradiol within 24–48 hours.
Widely available (though often obtained through non-pharmaceutical channels).
Bodybuilders prize it not just for gyno prevention, but also for achieving a harder, drier physique—a critical factor in competitive bodybuilding where symmetry, definition, and vascularity are judged at extremely low body fat levels (3–6%).
However, its misuse is rampant. Many athletes use it prophylactically at high doses without monitoring estradiol, leading to avoidable side effects.
5. Integration into Bodybuilding Cycles
Anastrozole is typically used during bulking or cruise phases involving aromatizable compounds. Here are common scenarios:
A. Testosterone-Only Cycle (e.g., 500–1000 mg/week Testosterone Enanthate)
Aromatization increases with dose.
At 500 mg/week: ~10–15% convert to E2. May not need AI.
At 750+ mg/week: AI often required.
Anastrozole use: 0.25 mg every 5–7 days, adjusted per labs.
B. Bulking Stack (Testosterone + Dianabol or Deca)
Dianabol is highly aromatizable; Deca less so but still contributes.
Higher E2 risk → AI often necessary.
Start AI at cycle onset if history of sensitivity.
C. Cutting Cycle (e.g., Testosterone Propionate + Trenbolone + Winstrol)
Trenbolone does not aromatize, but can mimic estrogenic effects via progestogenic activity.
Winstrol has anti-estrogenic properties.
Anastrozole rarely needed unless high-dose testosterone is included.
D. Post-Cycle Therapy (PCT)
Anastrozole is NOT used in PCT.
Instead, SERMs like tamoxifen (Nolvadex) or clomiphene (Clomid) are used to stimulate natural testosterone production.
Using anastrozole during PCT would further suppress estrogen, impairing recovery and increasing side effects.
7. Nutrition While Using Anastrozole
Nutrition plays a supporting role in managing AI-related side effects:
A. Joint Support
Omega-3 Fatty Acids (2–4 g/day): Reduce inflammation and support connective tissue.
Collagen Peptides (10–20 g/day, especially with vitamin C): Promote tendon and joint health.
Gelatin or bone broth: Natural sources of collagen precursors.
B. Bone Health
Calcium (1000–1200 mg/day) and Vitamin D3 (2000–5000 IU/day): Essential for bone mineralization.
Vitamin K2 (100–200 mcg/day): Directs calcium to bones, not arteries.
C. Liver Support
NAC (N-Acetylcysteine): 600–1200 mg/day—boosts glutathione, supports detox.
Milk Thistle (Silymarin): 200–400 mg/day—may protect hepatocytes.
Avoid alcohol completely during AI/steroid use.
D. Cholesterol Management
Increase fiber intake (oats, legumes, vegetables).
Consume healthy fats (avocado, olive oil, fatty fish).
Limit saturated fats and processed foods.
Consider red yeast rice or plant sterols if LDL rises significantly (under medical guidance).
E. Caloric & Macronutrient Strategy
Maintain adequate calories to support recovery, especially if joint pain increases energy needs.
Ensure 1.6–2.2g protein/kg/day, balanced carbs and fats.
Stay hydrated—AIs can contribute to dry joints and tissues
8. Additional Considerations
A. Blood Work is Non-Negotiable
I cannot stress this enough: Never use anastrozole without regular estradiol testing. Relying on symptoms alone leads to overuse. Use a lab that offers ultrasensitive estradiol assays (LC-MS/MS method), as standard tests are often inaccurate at low levels.
B. Alternatives to Anastrozole
Some athletes prefer milder compunds such as:
Arimistane (Androsta-3,5-diene-7,17-dione): Natural AI, less potent, fewer side effects.
Exemestane (an irreversible “suicide inhibitor”): Used mid-to-late cycle, but higher liver load.
Letrozole: Much stronger than anastrozole—not recommended for beginners due to high risk of crash.
C. Individual Variability
Genetics play a huge role in aromatization. Some men on 1000 mg/week testosterone need no AI; others on 500 mg need 0.5 mg anastrozole weekly. There is no universal protocol.
D. Legal and Ethical Note
Anastrozole is a prescription medication. Possession without a prescription is illegal in most countries. Sourcing from unregulated suppliers risks contamination, incorrect dosing, and legal consequences.
Final Thoughts: A Physician’s Perspective
As a doctor and performance consultant, my goal is not to enable or discourage steroid use, but to minimize harm and maximize informed decision-making. Anastrozole is a powerful tool when used correctly—like a scalpel. But in untrained hands, it becomes a chainsaw.
Bodybuilders must understand that estrogen is not the enemy. It is a vital hormone. The pursuit of ultra-low body fat and extreme muscle mass should not come at the cost of long-term joint health, mental well-being, or cardiovascular function.
If you choose to use anastrozole:
Get baseline and mid-cycle labs.
Start with 0.25 mg twice weekly or less.
Listen to your body—joint pain is a warning sign.
Support your liver, bones, and heart with nutrition and supplements.
Never use it during PCT.
And above all—consult a qualified medical professional.
Buy Anastrazole here