Gonadorelin: Complete Guide
Gonadorelin is the synthetic form of gonadotropin-releasing hormone (GnRH/LHRH), a decapeptide produced in the hypothalamus that controls the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland. It is used diagnostically (to evaluate pituitary-gonadal function) and therapeutically (to maintain HPG axis function during testosterone-suppressing therapies). Gonadorelin is FDA-approved under the brand name Factrel.
Last updated: 2026-01-29
Quick Facts
- Category
- therapeutic
- Also Known As
- GnRH, LHRH, Factrel
- Related Goals
- sexual health
Who Researches Gonadorelin?
Gonadorelin is researched by people interested in maintaining natural reproductive hormone production — particularly men on testosterone replacement therapy (TRT) who want to preserve testicular function and fertility. Unlike continuous GnRH agonists (leuprolide, goserelin) that paradoxically suppress LH/FSH through receptor desensitization, pulsatile gonadorelin stimulates the HPG axis. It's also relevant for researchers studying kisspeptin-GnRH-gonadotropin signaling and for fertility specialists using it as a diagnostic tool.
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What Is Gonadorelin?
Gonadorelin is identical to endogenous GnRH — a 10-amino-acid peptide (pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2) produced in the arcuate and preoptic nuclei of the hypothalamus. Endogenous GnRH is released in a pulsatile fashion (every 60-120 minutes), and this pulsatility is essential for its stimulatory effect on pituitary gonadotrophs.
The distinction between pulsatile and continuous GnRH administration is clinically critical: pulsatile GnRH stimulates LH/FSH release and maintains reproductive function, while continuous GnRH exposure causes receptor desensitization and paradoxically suppresses reproductive hormones — the basis for GnRH agonist drugs used in prostate cancer and endometriosis.
Mechanism of Action
Gonadorelin activates GnRH receptors (GnRHR) on pituitary gonadotroph cells:
- Pulsatile → stimulation: Intermittent GnRHR activation maintains receptor sensitivity, stimulating LH and FSH synthesis and release
- LH → testosterone: LH stimulates Leydig cells in testes to produce testosterone
- FSH → spermatogenesis: FSH supports Sertoli cells and sperm production
By mimicking natural pulsatile GnRH release, gonadorelin maintains the full HPG axis — including testicular function and fertility — even when exogenous testosterone would otherwise suppress it.
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Dosage Overview
| Application | Dose | Route | Frequency |
|---|---|---|---|
| Diagnostic (Factrel) | 100 mcg | IV or SC | Single dose |
| HPG axis maintenance | 100–200 mcg | SC | 2× daily or every other day |
For HPG axis maintenance during TRT, subcutaneous injection 2 times daily (mimicking pulsatile release) is the most common protocol. Use the peptide calculator for reconstitution.
Side Effects & Safety
- Generally very well-tolerated — mimics an endogenous hormone
- Injection site reactions: Mild and transient
- Headache: Occasionally reported
- Flushing: Transient
- Important: Continuous (non-pulsatile) administration will desensitize GnRH receptors and paradoxically suppress reproductive hormones — proper dosing intervals are critical