Can I inject this myself at home?

Prostap: yes, after a one-off training session in clinic and signed consent. Decapeptyl and Zoladex: no. Decapeptyl is a deep intramuscular injection and Zoladex is an implant placed under the abdominal skin, so both stay clinician-administered.

Prostap, Decapeptyl or Zoladex: what's the difference?

All three suppress testosterone equally well. Prostap is a subcutaneous depot and our most commonly prescribed option; Decapeptyl is an intramuscular injection; Zoladex is a small implant placed under the skin. The choice usually comes down to availability, what your administering clinic offers, and your own preference.

How is this different from a tablet blocker?

Tablets like cyproterone or spironolactone are taken daily and are cheaper, but rely on you remembering them and can bring drug-specific monitoring (liver, prolactin, potassium). A GnRH analogue is a single injection every few weeks giving the most complete, stable suppression, which is why it's often chosen for patients wanting maximum effect or minimal daily routine.

Will I stay on this forever?

Not necessarily. Many patients move to oestrogen alone once it suppresses testosterone adequately, and after orchidectomy or genital surgery the blocker is usually stopped altogether. We review it at each appointment.

When should I have my blood test?

Just before your next dose is due: that trough tells us suppression is holding across the whole cycle. Always note the date of your last injection on the form.

Home / Medication guides / GnRH Analogue Injections

TRANS-FEMININE HRT · MEDICATION GUIDE

GnRH Analogue Injections therapy, a clear guide.

GnRH analogues are the most effective testosterone blockers we prescribe. Rather than blocking the receptor, they switch off the pituitary signal that tells the testes to make testosterone, giving very low and very stable levels. Prostap can be self-administered at home after a one-off training session and signed consent; Decapeptyl and Zoladex are clinician-administered.

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Drug class

GnRH analogue

Route

SC (Prostap) / IM (Decapeptyl) / SC implant (Zoladex)

Frequency

Every 4-12 weeks

Administration

Prostap self-admin possible; Decapeptyl and Zoladex clinician-only

Effect

Very low testosterone

Reversible

Fully, on stopping

OVERVIEW

What gnrh analogue injections does, in plain English.

Prostap (leuprorelin), Decapeptyl (triptorelin) and Zoladex (goserelin) are the GnRH analogues used in UK gender care. All three work the same way: continuous stimulation of the pituitary paradoxically shuts down its release of the hormones (LH and FSH) that drive testosterone production. The result is testosterone suppressed to very low levels, which lets a lower, safer oestrogen dose do the feminising work.

Prostap is our most commonly prescribed option, given as a subcutaneous depot injection, typically 11.25 mg every 12 weeks (a 3.75 mg 4-weekly form also exists). Patients can be trained to self-administer Prostap at home after a one-off training session and signed consent. Decapeptyl is an intramuscular injection, 11.25 mg every 12 weeks (a 3 mg monthly form also exists) and is clinician-administered. Zoladex is a small depot implant placed under the skin of the abdomen, 10.8 mg every 12 weeks, also clinician-administered.

HOW IT WORKS

The way it actually works.

For the first week or two a GnRH analogue actually stimulates testosterone (the "flare") before it downregulates the pituitary and suppression sets in. We plan around that, sometimes overlapping an oral blocker over the first cycle. From then on, levels stay low and stable until the next dose is due.

Acts at the pituitary

Shuts down the LH/FSH signal that drives the testes, so production falls at the source.

Very stable levels

One dose covers weeks: no daily tablet, and none of the peaks and troughs.

Plan for the flare

A brief early testosterone rise is expected and managed, often with a short oral-blocker overlap.

Fully reversible

Production resumes once you stop; the effect is not permanent.

SIDE EFFECTS & RISKS

What to watch for, and what to tell us.

GnRH analogues have a favourable safety profile and are well tolerated. Most effects come from low testosterone itself and are shared with the other blockers; a couple are specific to the injection or implant.

Common

Lower libido and erections +

Expected with strong testosterone suppression.

Hot flushes +

Especially early, before oestrogen is fully established. They settle as oestrogen builds.

Injection / implant-site reactions +

Soreness, bruising or a small lump at the site for a few days.

Fatigue or mood dips +

Some patients feel flatter around the changeover; tell us if it persists.

Less common / serious

Testosterone flare +

A brief rise in the first 1-2 weeks before suppression. Planned for, and rarely a problem in practice.

Bone density +

Prolonged very-low sex-hormone levels can thin bone, but adequate oestrogen protects against this, which is why the two are prescribed together.

Monitoring schedule

We catch things early. Here's the routine you can expect.

Most of the testing is front-loaded while we fine-tune your dose. Once your levels are stable, it's usually just once a year.

Baseline

Testosterone & oestradiol

FBC, U&E, LFTs

Blood pressure

3–6 months

Testosterone (suppression)

Oestradiol level

6-monthly while adjusting

Testosterone & oestradiol

LFTs

Yearly once stable

Full hormone panel

Symptom & dose review

COST

What gnrh analogue injections costs you, monthly.

GnRH analogues cost more than oral blockers privately, but only four doses a year are needed. Once your GP prescribes under shared care, the cost drops to the standard NHS prescription charge. The figures below are approximate; confirm with your pharmacy.

Prostap (private)

~£70-90 per 12 weeks

Leuprorelin 11.25 mg

Decapeptyl (private)

~£70-90 per 12 weeks

Triptorelin 11.25 mg

Zoladex (private)

~£80-100 per 12 weeks

Goserelin 10.8 mg implant

Once on shared care

£9.90 per item

Standard NHS Rx charge

See full payment plan

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