GnRH agonist

Also written as long protocol drug

Written by Zayn Miah & R KhanomLast updated 17 September 2026Not clinically reviewed

A medication that initially stimulates then suppresses the pituitary gland's release of hormones that trigger ovulation.

In plain English

It's a drug that first switches your natural cycle on, then turns it right down, so your clinic can fully control your stimulation.

Why it matters

It's the basis of the 'long protocol', started before your period in the cycle before stimulation begins.

Related terms

Guides that cover this

Written by patients, not clinicians. This page has not yet been reviewed by a named fertility professional, so it explains published guidance and points you to the original source instead of giving medical advice. It is not medical advice. Decisions about your treatment belong with your own clinic. Read our editorial policy and corrections policy.