PCT Explained: SERMs vs Aromatase Inhibitors

📅 June 19, 2026 ⏱️ 3 min read ✍️ Team TPS

SERMs and aromatase inhibitors are both called “estrogen control”, which is why they get confused. They do opposite things to estrogen, and using the wrong one at the wrong point is one of the more common PCT mistakes.

The core difference

An aromatase inhibitor (AI) reduces how much estrogen exists. It blocks the aromatase enzyme that converts testosterone into estradiol, so less estrogen is produced in the first place. Arimidex (anastrozole) and letrozole are AIs.

A SERM does not reduce estrogen. Estrogen levels stay where they are, a SERM blocks the receptor in some tissues while leaving it active in others. Tamoxifen (Nolvadex) and clomiphene (Clomid) are SERMs.

That distinction drives everything else: an AI lowers systemic estrogen, with the knock-on effects that carries for lipids, joints and mood. A SERM leaves it circulating and just changes where it can act.

When each is used

On cycle, an AI is the usual tool for managing estrogenic side effects from aromatising compounds, because the goal is genuinely to have less estrogen.

After cycle, SERMs do the heavy lifting. Blocking estrogen receptors at the hypothalamus removes the negative feedback suppressing LH and FSH, which restarts natural testosterone production. Clomid and tamoxifen are the standard pairing for exactly this reason. See the SERMs and AIs range.

Why an AI is the wrong tool for PCT

This is the mistake worth naming. Crushing estrogen with an AI during PCT feels intuitive, but estrogen is part of the signalling loop you are trying to restart, and very low estrogen carries its own costs: lipid profile, joints, libido and mood all suffer.

SERMs restart the axis without flattening estrogen systemically. That is the job they are built for.

Where HCG fits

HCG is neither. It mimics LH and acts directly on the testes, which makes it a maintenance tool during a cycle or a primer before PCT rather than part of PCT itself. Running HCG alongside a SERM during PCT works against the recovery you are trying to trigger, because you are still supplying an external signal. Stocked in fertility and libido support.

The practical shape of a protocol

Broadly: AI during the cycle if the compounds aromatise; HCG during or before the taper if used at all; SERMs after clearance to restart the axis. The specifics: timing, duration, which compounds: depend entirely on what was run and for how long, and that is a conversation to have with someone who knows your bloodwork rather than a number to copy from an article.

Browse the full PCT and hormonal support range.

Supplied for research purposes only. This article is informational and is not medical advice. Bloodwork before and after is the only way to know what is actually happening.