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Experimental/GnRH AntagonistResearch peptide

Cetrorelix

aka Cetrotide

GnRH receptor antagonist used to prevent premature ovulation in IVF cycles.

Educational explainer of a research peptide. Profiles in this section deliberately omit clinical-trial citations, dosing protocols, and purchase links. Not FDA-approved as a supplement; not a recommendation to use.

Overview

Cetrorelix is a synthetic decapeptide GnRH receptor antagonist used as an injectable in assisted reproduction.

Source
  • Approved pharmaceutical
Forms
  • Subcutaneous injection

Mechanism of action

Competitively blocks pituitary GnRH receptors, rapidly suppressing LH and FSH release without an initial flare.

Pathways
  • · GnRH receptor antagonism
  • · LH and FSH suppression
Hormones
  • · GnRH
  • · LH
  • · FSH

How it acts on the body

Unlike GnRH agonists, antagonists produce immediate suppression with no flare phase. In IVF, cetrorelix is started mid-cycle to block the LH surge while controlled ovarian stimulation continues, preventing premature ovulation and allowing the team to time egg retrieval precisely.

Recovery of the HPG axis is rapid after discontinuation, which is important for the embryo transfer window in IVF protocols.

Hormonal & endocrine impact

How this peptide is reported to shift specific hormones and signaling molecules. Directionality reflects research literature and preclinical models, not clinical prescribing data.

Projected hormonal trajectory
Illustrative curves derived from reported direction of effect. Not measured patient data.

Curves are schematic shapes (sigmoid for increases/decreases, damped oscillation for modulation/stabilization) anchored to a 100% baseline. They communicate direction and tempo of change reported in research literature — not absolute hormone concentrations.

LHDecreases
Rapid suppression preventing premature surge.
FSHDecreases
Modest suppression.
EstradiolStabilizes
Continues to rise from exogenous gonadotropins despite GnRH blockade.

Effects on the body

Inhibits
Premature LH surge during ovarian stimulation

Organ system effects

Endocrine

Pituitary GnRH receptor blockade.

Reproductive

Cycle control in IVF.

Reported effects

Drawn from preclinical research, anecdote, and small-scale clinical observation. No evidence grades are assigned — most peptides on this page lack rigorous human trials.

  • No flare phase
  • Rapid onset and offset

Potential side effects

Common
  • · Local injection-site reaction
  • · Mild nausea
Rare
  • · Headache
Serious
  • · Ovarian hyperstimulation syndrome from concurrent stimulation

Drug interactions

No notable interactions reported.

Pairing context

Often combined with
  • Controlled ovarian stimulation protocols
    Designed for that use.
Avoid combining with
  • Known hypersensitivity to GnRH peptides
    Cross-reactivity risk.
Important. Research peptides described here are not FDA-approved supplements. Supplement Scholar does not endorse, recommend, or link to any source for purchase. Consult a qualified clinician before considering any peptide therapy.