Monotherapy

Monotherapy means taking a single hormone medicine rather than a combination. In feminizing care it usually means [estradiol](/glossary/estradiol) alone, with no separate [anti-androgen](/glossary/anti-androgen), relying on the estrogen itself to bring testosterone down.

Where you'll meet it

In comparisons between feminizing plans, especially in the US, where some prescribers use injectable estradiol on its own, and in forum threads where people ask whether they can drop their blocker. You will also see it after an orchiectomy or a vaginoplasty that removes the testes, when most people stop their anti-androgen under their prescriber's guidance because there is no longer much testosterone to suppress.

Masculinizing therapy is almost always monotherapy already: testosterone alone, because at a high enough level it overrides the ovaries' estrogen without a separate blocker. That is why the word rarely comes up there.

How it works

The brain and the gonads run on a feedback loop. When the brain senses enough sex hormone in the blood, it turns down the signal telling the testes to make testosterone. High enough estrogen triggers that same brake, so testosterone falls without a second medicine.

The catch is "high enough". For estrogen alone to suppress testosterone reliably, estradiol levels generally need to sit towards the upper end of what prescribers aim for, and that is easier to reach with injections than with tablets, patches or gel. Some prescribers are comfortable with that; others are more cautious, because it means running estrogen higher than they otherwise would, and higher estrogen adds clot risk. Estrogen covers the routes.

How you know it is working

Blood tests answer it. What matters is both numbers: estradiol, and whether testosterone has come down to the level your prescriber is aiming for, commonly given as under about 50 ng/dL (under about 1.7 nmol/L). If testosterone stays above target, a prescriber may add a blocker after all or change the route. With injections, the timing of the test matters, because levels are highest a day or two after a dose and lowest before the next; peak and trough explains why, and how to read your hormone blood results covers units.

Why people choose it

To avoid the side effects of a separate blocker: the frequent urination, light-headedness and potassium checks of spironolactone, or the meningioma, mood and prolactin concerns of cyproterone. Fewer medicines also means fewer things to run out of. For others the reason is simply that testosterone is already low after surgery.

Common questions

"Monotherapy means a weaker plan." Not if testosterone is suppressed. It is the level that matters, not the number of medicines.

"Anyone can just stop their blocker." Not safely on your own. Whether estrogen alone is enough depends on your route and levels, and testosterone comes back if it is not. That is a decision to make with your prescriber and a blood test.

"More estrogen gives faster results." It does not. Levels well above target mostly add risk.

What to ask

If you are interested, ask your prescriber whether your current estradiol level would suppress testosterone on its own, which route they would use to get there, and how they would check. Anti-androgens sets out the options side by side.

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