Arimidex vs Aromasin vs Letrozole

📅 July 10, 2026 ⏱️ 3 min read ✍️ Team TPS

Anastrozole, exemestane and letrozole all lower oestrogen, and they are not interchangeable. They differ in how they bind, how hard they hit, and how forgiving they are when you get the amount wrong.

Two mechanisms, not one

Reversible inhibitors, anastrozole and letrozole, occupy the aromatase enzyme temporarily. Stop taking them and the enzyme resumes work, which is why a sharp rebound is possible.

Suicidal inhibitors, exemestane, bind permanently. That enzyme is finished; the body has to make new ones. The practical result is less rebound on cessation.

Anastrozole: the default

Anastrozole is the usual first choice because it is predictable and comparatively easy to titrate. It is potent enough for most aromatising cycles without being so aggressive that a small error becomes a problem.

The failure mode is over-suppression, which is unpleasant and easy to reach.

Exemestane: fewer rebound problems

Exemestane’s permanent binding is its distinguishing feature. It is also reported to be kinder to lipids than the reversible inhibitors, which matters on a long run.

It is the more forgiving option on cessation, which is why it is often preferred running into a recovery phase.

Letrozole: rarely the right first answer

Letrozole is powerful, powerful enough to flatten oestrogen entirely with very little provocation.

That makes it a tool for a specific problem, usually an acute one, rather than a general-purpose control. Used casually it produces exactly the crash people are trying to avoid.

Oestrogen is not the enemy

This is the part that gets lost. Oestrogen is required for joint comfort, libido, mood, bone density and lipid health. Crushing it produces a distinct and thoroughly miserable set of symptoms: flat mood, dry aching joints, no libido.

The goal is control, not elimination, and the only way to know where you are is bloodwork, because low-oestrogen and high-oestrogen symptoms overlap enough to be routinely confused for one another.

An AI is not PCT

An aromatase inhibitor manages oestrogen while compounds are running. It does not restart natural production, which is what a SERM is for. Using an AI as recovery is a common and costly misunderstanding, SERMs vs aromatase inhibitors covers why, and clomid vs nolvadex covers the SERM choice.

Which to use

Anastrozole for routine control on an aromatising cycle. Exemestane where rebound or lipids are the concern, or running into recovery. Letrozole only for a specific acute problem, and carefully.

Note also that not every cycle needs one at all, the dry compounds do not aromatise. Dianabol needs one; masteron does not.

Supplied for research purposes only.