Estrogen Blockers

Estrogen blockers: two classes, commonly confused

Estrogen blockers bodybuilding discussions usually merge two drug classes that do quite different things. Getting the distinction right determines whether the compound you buy addresses your actual problem. This section holds 77 lines from £25 to £120, clustered near £55.

Which one do you need?

Aromatase inhibitors against SERMs

	Aromatase inhibitors	SERMs
Examples	Anastrozole, exemestane, letrozole	Tamoxifen, clomiphene
Mechanism	Blocks the aromatase enzyme	Occupies the oestrogen receptor
Blood oestradiol	Lowered	Unchanged
Addresses water retention	Yes	No
Restarts LH and FSH	No	Yes
Usual phase	On cycle	After cycle

The short version: an inhibitor lowers oestrogen, a SERM blocks it at specific receptors. Using a SERM to control bloating does not work, because circulating oestradiol has not moved.

The mistake that matters most

Dosing without measuring. Aromatisation varies enormously between people and compounds, and crashed oestradiol produces joint pain, lost libido, worsened lipids and flat mood — frequently mistaken for the cycle underperforming, which prompts exactly the wrong correction. Oestrogen is necessary; the goal is a normal range, not zero.

Timing across a cycle

An inhibitor runs during the cycle, started alongside it and adjusted from a blood reading around week three. A SERM runs afterwards, once the suppressive compound has cleared. Carrying an inhibitor into the recovery phase works against the SERM, because suppressing oestrogen while trying to restart signalling pulls in opposite directions.

What is stocked in this section

The 77 lines here span both classes, priced £25 to £120 with a midpoint of £55. Intex Pharma and Mactropin are the most represented manufacturers. Because the section mixes inhibitors and SERMs, checking which class a listing belongs to before ordering matters more here than in most categories.

When you need neither

Non-aromatising compounds — stanozolol, trenbolone, drostanolone — produce no oestrogen to control. Adding an inhibitor there crashes oestradiol for no reason. With trenbolone the relevant pathway is prolactin instead, which needs cabergoline, not an inhibitor.

The three inhibitors are compared in anastrozole versus exemestane versus letrozole. Recovery compounds sit in post cycle therapy.

One further point worth stating: neither class does anything about prolactin, which is a separate pathway raised by 19-nor compounds and needing cabergoline instead. Misreading prolactin symptoms as oestrogenic is among the commonest errors in this area.

Frequently asked questions

Why do bodybuilders take oestrogen blockers?
To manage the oestrogenic consequences of aromatising compounds, and to restart suppressed production afterwards. Two different jobs, two different drug classes.

Which is better, an AI or a SERM?
Neither — they do different things. An AI on cycle, a SERM afterwards.

Do I need one on every cycle?
Only with aromatising compounds, and only if oestradiol is measurably elevated.

What does crashed oestrogen feel like?
Aching joints, no libido, flat mood and lethargy — often mistaken for the cycle not working.

Will an AI help with trenbolone gyno?
No. Trenbolone does not aromatise; the pathway is prolactin, which needs cabergoline.