Gonadorelin (Factrel / Lutrelef)
Synthetic 10-aa GnRH – direct pituitary GnRH-R stimulus, LH/FSH release. FDA Factrel 1982 (US-discontinued 2008); EMA Lutrelef pulsatile-pump Rx for hypothalamic hypogonadism. Continuous dose paradox-downregulation in prostate cancer therapy.
WHAT IS GONADORELIN (FACTREL / LUTRELEF)?
Detailed overview
Gonadorelin is a synthetic replica of the 10-amino-acid decapeptide GnRH (gonadotropin-releasing hormone, also known as LHRH) – sequentially IDENTICAL to endogenous hypothalamic GnRH (pyroGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH₂). The hypothalamic arcuate nucleus + median eminence GnRH neurons naturally secrete GnRH in a ~90-120-minute pulsatile pattern into the hypothalamo-pituitary portal circuit; SC or IV injection of Gonadorelin replicates this pulse signal and binds directly to the GnRH receptor on pituitary anterior-lobe gonadotrope cells → LH + FSH release. **Clinical history**: FDA Factrel approval (Wyeth 1982) – original indication was pituitary LH/FSH diagnostic stimulation testing (to discriminate hypothalamic vs pituitary hypogonadism). US discontinued 2008 (commercial-viability reasons, NOT safety). EMA Lutrelef (Ferring) remains available across the EU on a pulsatile-pump protocol as an Rx for hypothalamic hypogonadism (Kallmann syndrome + acquired GnRH deficiency). **Paradox mechanism with continuous dosing**: a chronically elevated GnRH signal (vs pulsatile) downregulates the GnRH receptor → this is the mechanism of GnRH-agonist therapy in prostate cancer treatment (Lupron/Leuprolide, Zoladex/Goserelin) – same molecular family, opposite-direction effect based on the dosing pattern. **AAS-PCT context**: Gonadorelin sits 1 axis level below Kisspeptin-10 (Kisspeptin upstream GPR54 → GnRH stimulus; Gonadorelin direct pituitary GnRH-R stimulus). The practical problem is identical: pulsatile-pump impractical for self-administration, single bolus has limited efficacy. UGL peptide sourcing is standard; EU pharmacy availability via Lutrelef protocol.
Mechanism
Direct pituitary anterior-lobe GnRH-receptor (LHRH-R) agonist → LH + FSH release → testicular Test
Dosing
100 mcg SC every 90-120 min (pulse-pump, impractical) or 100-500 mcg SC bolus pre-cycle (community protocol, limited efficacy)
Half-life
~10-40 min (very short – pulsatility pattern is essential)
Onset
LH/FSH spike 15-60 min after SC
Legal status
FDA Factrel withdrawn 2008; EMA Lutrelef Ferring Rx (pulsatile-pump hypothalamic hypogonadism); WADA S2 Peptide Hormones banned
Data console
Lab data
Safety
Side effects, stop signs, contraindications
Side effects · 6
- Hypersensitivity reactions, including rare anaphylaxis and antibody formation with repeated parenteral dosing (documented in FDA Factrel labeling: generalized urticaria, bronchospasm).
- Injection-site reactions: pain, redness, itching, swelling, rarely phlebitis; with pulsatile-pump protocols, ongoing cannula-site inflammation and infection risk.
- Headache, flushing, mild dizziness and nausea, often immediately post-injection, transient.
- Abdominal pain and discomfort, less commonly gastric complaints (reported in FDA Factrel labeling).
- With continuous (non-pulsatile) or prolonged dosing, paradoxical GnRH-receptor downregulation and desensitization: LH/FSH suppression and falling testicular testosterone (the chemical-castration mechanism of GnRH-agonist therapy).
- With pulsatile-pump protocols, overstimulation from increased gonadotropin drive: multiple follicular development and risk of ovarian hyperstimulation in women; transient secondary estradiol rise in men.
Contraindications · 6
- Known hypersensitivity to gonadorelin or GnRH analogues (prior anaphylactic or severe allergic reaction).
- Hormone-sensitive tumor or suspicion thereof (gonadotropin- or sex-hormone-dependent tumor) where LH/FSH stimulation is contraindicated.
- Pituitary adenoma, especially prolactinoma or gonadotroph tumor: GnRH stimulation carries a risk of pituitary apoplexy and abrupt hormone surge.
- Concurrent GnRH-agonist therapy (leuprolide/Lupron, goserelin/Zoladex): receptor-occupancy overlap and amplification of paradoxical receptor downregulation – not recommended.
- Pregnancy and breastfeeding: no established safety, axis stimulation not indicated; in fertility treatment only under endocrinologist supervision.
- Not indicated for self-treatment as AAS-PCT: pulsatile pump is impractical for self-injection, bolus protocol is evidence-poor, and lack of sterile technique creates infection risk.
Related Performance Compounds
Same therapeutic category
Studies
Related research and clinical findings
Factrel (gonadorelin hydrochloride) for injection – FDA Label
Wyeth-Ayerst Laboratories
Lutrelef (gonadorelin acetate) – EMA Summary of Product Characteristics
Ferring Pharmaceuticals
Therapeutic effects of a pulsatile GnRH pump on adult male patients with congenital hypogonadotropic hypogonadism (CHH): a retrospective study.
Jiang H, Li BJ, Jin DC
[Effect and safety of pulsatile GnRH therapy for male congenital hypogonadotropic hypogonadism].
Niu YH, Xu H, Chen YW
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