SERMs vs. AIs: When to Use Each

In the context of anabolic steroid use, managing estrogen is essential to minimize unwanted side effects. Two primary classes of compounds are used for this purpose:

• SERMs (Selective Estrogen Receptor Modulators)
• AIs (Aromatase Inhibitors)

Each has distinct mechanisms and use-cases that are vital to understand for any bodybuilder planning a cycle or post-cycle therapy (PCT).

• SERMs block estrogen from binding to receptors in select tissues, such as breast tissue, without lowering systemic estrogen levels.
• AIs inhibit the aromatase enzyme responsible for converting androgens (e.g., testosterone) into estrogen, thereby lowering total estrogen levels in the body.

AIs are used primarily on-cycle to manage systemic estrogen increases caused by aromatization.

Symptoms of high estrogen include:

• Gynecomastia (gyno)
• Water retention
• High blood pressure
• Mood swings or emotional instability
• Erectile dysfunction

Common AIs and notes:

• Anastrozole (Arimidex) – Effective in small doses; too much can crash estrogen
• Exemestane (Aromasin) – Suicidal AI, less risk of rebound; generally well-tolerated
• Letrozole – Extremely potent; best reserved for severe gyno cases

Tips:

• Start at low doses and titrate based on symptoms or bloodwork
• Excessive estrogen suppression can result in:
  1. Joint pain
  2. Depression
  3. Low libido

SERMs are best used:

• During Post-Cycle Therapy (PCT) to restore natural testosterone production
• To treat already developed gynecomastia

Functions:

• Stimulate LH and FSH to restart natural testosterone production
• Block estrogen at the receptor level (not systemic E2 reduction)

Common SERMs and notes:

• Tamoxifen (Nolvadex) – Primary SERM for gyno treatment and PCT
• Clomiphene (Clomid) – Strong HPTA stimulator; often stacked with Nolvadex
• Raloxifene – Used primarily for gyno; preferred by some due to fewer side effects

Limitations:

• SERMs do not lower estrogen levels in the bloodstream
• Not effective for controlling water retention or emotional side effects on-cycle

• “Always keep an AI on hand when running a test-based cycle.”
• “At the first sign of sensitive nipples, run Tamoxifen ASAP.”
• “Too much AI = no libido and dry joints. Been there.”
• “Ralox worked better than Nolva for me when reversing early gyno.”

While some users combine SERMs and AIs, it's typically not necessary.

Recommended practice:

• On-Cycle: Use AIs as needed to manage estrogen
• PCT: Use SERMs like Nolvadex and Clomid to restart natural testosterone

Note:

• Using both simultaneously may increase side effects unnecessarily
• AIs should not be run during full SERM-based PCT

Always confirm estrogen levels via sensitive E2 blood testing (not standard E2).

• Ideal E2 range: 20–40 pg/mL
• <15 pg/mL: Symptoms of low estrogen
  1. Fatigue
  2. Low libido
  3. Dry joints
• >50 pg/mL: Risk of estrogenic side effects
  1. Bloating
  2. Mood swings
  3. Gyno

• Use AIs to manage estrogen levels during a cycle
• Use SERMs to restore testosterone production post-cycle
• Don't confuse receptor blockade with systemic estrogen reduction
• Always have both on hand before starting a cycle
• Adjust based on bloodwork, side effects, and compound dosages

Proper use of SERMs and AIs ensures safety, effectiveness, and long-term hormonal health for steroid users.