GnRH agonist vs antagonist

[Scottishgirl85]

Sorry I'm creating a lot of new threads recently, but the knowledge on this board is amazing and I'm in the mad research pre-ivf phase where Google is not providing the answers...

Can someone please tell me the difference between GnRH agonist vs antagonist protocol? Is this equivalent to long protocol vs short protocol? Or is it simply different ways of stimulating, i.e. either could be used as part of short or long protocol?

From what I can see the antagonist version is slightly shorter in treatment duration, and more suited to older patients or PCOS (I'm 31, no PCOS), but my clinic says it 'uses lower doses of stimulating hormones', so I like the idea of it. We have severe MFI, I check out ok.

Any help would be hugely appreciated!! Hopefully one day I can become an 'expert' and help others on here! x

[freelancescientist]

Antagonist cycles are usually the 'short' protocols. The agonist protocols normally need a period of downregulation before you start your stimulation drugs. Antagonist cycles you start your stimulation drugs then add in the antagonist.
Each clinic has their own protocols and will decide which you should have looking at things like ovarian reserve, cause of infertility, age etc.

[bananafish81]

Agonist can be usually long protocol, or occasionally short agonist (aka short flare protocol). This is relatively uncommon

Long agonist is taking the agonist for down reg before stims

Short agonist is starting the agonist alongside stims. The agonist gives an initial flare of FSH and LH (hence flare protocol) before it kicks into suppression mode

Antagonist protocol is what is normally referred to as short protocol. Whereas an agonist takes a while for the suppressive effect to kick in, an antagonist works very quickly to slam the brakes on

Long agonist is the default for women with normal ovarian reserve

Short antagonist tends to be the protocol of choice for both (counterintuitively) poor responders (low AMH) and high responders (high AMH / PCOS)

Short flare is occasionally used for poor responders