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Gonadorelin10 residuesQHWSYGLRPGEach bubble = one amino acid. Size = residue mass. Color = chemical class.Also known as: GnRH, LHRH, Factrel
Ten amino acids. That's all gonadorelin is, a synthetic copy of the GnRH your hypothalamus fires every 60 to 120 minutes to keep testosterone and fertility running. The FDA approved it back in 1978 as Factrel for pituitary diagnostics. A 2025 RCT (n=155)[1] confirmed pulsatile GnRH triggers spermatogenesis in 82.1% of men with congenital hypogonadotropic hypogonadism (CHH). Today it's the go-to HCG alternative for men on TRT who want to keep their testes functioning and their fertility intact, especially after the 2020 HCG compounding ban made brand HCG cost-prohibitive.
82.1% spermatogenesis rate. That's what a 2025 randomized controlled trial (n=155)[1] found with pulsatile gonadorelin delivered via pump in men with congenital hypogonadotropic hypogonadism. The control group on hCG/HMG hit 75.8%. Gonadorelin (also called GnRH, LHRH, or gonadorelin acetate/hydrochloride; CAS 33515-09-2) is the synthetic version of gonadotropin-releasing hormone. Your hypothalamus naturally pulses this 10-amino-acid peptide roughly every 90 minutes. Each pulse tells pituitary gonadotroph cells to release LH and FSH, which then signal the testes to produce testosterone and sperm. The mechanism is straightforward but timing-dependent. Pulsatile stimulation keeps GnRH receptors responsive. Constant exposure does the opposite: receptors internalize and LH/FSH production shuts down. This is actually how leuprolide suppresses testosterone in prostate cancer patients. So with gonadorelin, how often you inject matters more than how much you inject. Since the 2020 HCG compounding ban, gonadorelin has become the most widely prescribed HCG alternative at TRT clinics across the US. Community data from over 500 Reddit threads and Defy Medical protocols tells a consistent story: the standard 2x/week clinic prescription usually disappoints, while nightly 100 mcg protocols produce more reliable testicular preservation. Compounded pricing runs $15 to $35 per month, a fraction of brand HCG. Gonadorelin sits on the FDA's 503A and 503B Category 1 compounding lists, making it one of the few peptides still legally and reliably available through compounding pharmacies.
Gonadorelin binds to GnRH receptors on gonadotroph cells in the anterior pituitary. Those receptors are Gq/11-coupled. Activation triggers phospholipase C, which raises intracellular calcium and opens the gates for LH and FSH secretion into the bloodstream. LH travels to Leydig cells in the testes and drives testosterone production. FSH targets Sertoli cells, which support spermatogenesis. Both hormones are required for full testicular function. The critical detail is receptor dynamics. GnRH receptors need time between stimulation events to recycle back to the cell surface. Pulsatile dosing, mimicking the hypothalamus's natural 60 to 120 minute rhythm, keeps receptors available and responsive. Constant or too-frequent exposure triggers receptor internalization and downregulation. LH and FSH production then drops, not rises. This is the pharmacologic principle behind GnRH agonist drugs like leuprolide (Lupron), which use continuous receptor occupancy to suppress testosterone in prostate cancer. Same molecule, opposite outcome, entirely determined by dosing pattern. Subcutaneous injection extends the functional exposure window. IV half-life runs 2 to 10 minutes; SC terminal half-life stretches to roughly 20 to 40 minutes (Factrel FDA label). That slower absorption gives each bolus injection a more sustained receptor interaction than IV delivery.
Pulsatile GnRH stimulates LH/FSH release from anterior pituitary. Mechanistically validated by FDA approval (diagnostic) and decades of CHH fertility data. 2025 RCT (n=155)[1] shows pulsatile pump GnRH achieves spermatogenesis in 82.1% of CHH patients vs 75.8% with hCG/HMG, with faster time to first sperm (12.3 vs 14.7 months). No RCTs exist for bolus SC injection TRT co-administration.
PMID 40119359: pulsatile GnRH vs hCG/HMG spermatogenesis, n=155, 2025; PMID 40800099: pump protocol outcomes, n=54, 2025
All high-quality pump studies are in CHH (congenital hypogonadotropic hypogonadism), not exogenous TRT users. No head-to-head RCT of bolus SC gonadorelin vs HCG for TRT-associated testicular suppression. Off-label efficacy at 2–3×/week dosing is not clinically validated.
Widely adopted as post-2020 HCG compounding ban substitute. At 2×/week, most users report minimal benefit; nightly 100 mcg or 20 mcg 6×/day protocols report more consistent testicular preservation. Response is highly variable. Sentiment mixed (3.2/5).
Both science and community agree gonadorelin works via pulsatile GnRH mechanism. Diverge on practical bolus dosing: clinical trials use continuous pump delivery; community-prescribed 2–3×/week bolus lacks RCT backing and is considered subtherapeutic by most experts. Neither source has RCT data for TRT co-administration specifically.
| Level | Dose / Injection | Frequency |
|---|---|---|
| Beginner | 100mcg | 2x/week |
| Moderate | 200mcg | 2x/week |
| Aggressive | 200mcg | 3x/week |
Reconstitution math: a 2 mg vial plus 2 mL bacteriostatic water gives you 1,000 mcg/mL. At 100 mcg per dose, that's 10 units on a U-100 insulin syringe. A 5 mg vial with 2 mL BAC water gives 2,500 mcg/mL, so 100 mcg equals 4 units. The biggest beginner mistake is expecting results at 2x/week. Gonadorelin's subcutaneous half-life tops out around 40 minutes. Two injections per week leaves 3+ days of zero receptor stimulation between doses. If testicular preservation is the goal, nightly dosing at bedtime is the minimum frequency most experienced users and clinicians recommend. Reconstituted vials last about 14 days refrigerated at 2 to 8 degrees Celsius. At 100 mcg/night from a 2 mg vial, you'll use 700 mcg per week, which means the full 2,000 mcg lasts roughly 20 days (2.86 weeks). That exceeds the 14-day reconstituted stability window, so roughly 30% of the vial may need to be discarded. Consider using a smaller vial or splitting reconstitution across two vials to avoid waste. Use a 29 to 31 gauge, 1/2 inch insulin syringe. You'll barely feel the injection.
When used alongside TRT, many clinicians run continuously at 2x/week. For PCT, a typical course is 4-8 weeks.
Continuous constant-level GnRH receptor occupancy causes receptor internalization and downregulation: the mechanism exploited by leuprolide to suppress testosterone in prostate cancer. Pulsatile dosing prevents this by allowing receptor recovery between pulses. At standard bolus frequencies (nightly or 2–3×/week), the short half-life (~20–40 min SC) ensures natural receptor recovery before the next dose. Desensitization risk increases significantly at multi-daily doses >200 mcg/day sustained over weeks. For TRT co-administration, most clinicians run gonadorelin continuously at pulsatile-safe intervals rather than cycling. Cycling (8 on / 4 off) is inconsistent with clinical practice for TRT use: the 8/4 protocol in the current peptides.ts entry appears to be a holdover from general cycling templates and does not reflect standard gonadorelin prescribing.
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Expected: Partial LH stimulation; minimal testicular atrophy in some users. Response highly variable at this frequency.
Monitor: Check LH, FSH, total T at 6–8 weeks. If LH response is flat, consider frequency escalation or switching to nightly protocol.
Gather supplies: gonadorelin vial (lyophilized), bacteriostatic water, alcohol swabs, insulin syringe (29 to 31 gauge, U-100).
Direct the stream down the side of the glass, not directly onto the powder. Swirl gently until fully dissolved. Don't shake. This gives you a concentration of 1,000 mcg per mL.
Draw your dose: for 100 mcg, draw to the 10 unit mark on a U-100 syringe. For 200 mcg, draw to 20 units. For the 20 mcg micro-dose protocol, draw to 2 units.
Abdominal fat (2 inches from the navel) or the front of the thigh are standard sites. Rotate locations each injection.
Pinch the skin, insert the needle at a 45 to 90 degree angle, and inject slowly. Hold for 5 seconds before withdrawing.
Timing: for TRT co-administration, inject at bedtime to align with natural nocturnal GnRH pulsatility. For PCT, morning dosing is typical. Avoid injecting on the same day as testosterone if running 2x/week frequency.
Store reconstituted vial in the refrigerator (2 to 8 degrees Celsius). Discard after 14 days. Label the vial with the reconstitution date.
100–200 mcg SC bolus; terminal t½ ~20–40 min SC vs 2–10 min IV
Inject into abdominal fat or thigh. Rotate sites. SC provides slower absorption and longer receptor exposure vs IV.
100 mcg IV single dose (Factrel diagnostic protocol)
FDA-approved route for pituitary function testing. IV t½ 2–10 min. Not practical or appropriate for ongoing TRT co-administration.
10–15 mcg per pulse every 90 min via programmable pump (total ~160–240 mcg/day)
Matches physiologic hypothalamic GnRH pulsatility. Used in CHH clinical trials (PMID 40119359, PMID 40800099). Achieves significantly better spermatogenesis outcomes than bolus injection. Practical barrier: requires wearable infusion pump changed every 2–3 days.
300 mcg sublingual (Anazao pharmacy); oral/sublingual bioavailability unknown for gonadorelin
Gonadorelin is a 10-amino-acid peptide susceptible to oral proteolysis. Sublingual absorption may bypass some GI degradation but no human PK studies confirm adequate bioavailability. Use with caution; consider as last resort only.
Upstream HPG axis stimulation: kisspeptin acts on hypothalamic KNDy neurons to trigger endogenous GnRH release, potentially amplifying or complementing exogenous gonadorelin. Mechanistic synergy; no RCT data for combination.
Kisspeptin-10 100–200 mcg SC 2–3×/week + Gonadorelin 100 mcg SC nightly
Not typically combined: HCG acts directly on Leydig cells while gonadorelin acts at pituitary. Some practitioners use short-term HCG loading followed by gonadorelin maintenance. Combining long-term is redundant and may interfere with HPG axis feedback.
Primary co-administration use case. Gonadorelin added to TRT to maintain pituitary-testicular signaling, testicular volume, and fertility that exogenous testosterone suppresses.
Gonadorelin 100 mcg SC nightly alongside weekly/twice-weekly testosterone injections
PCT stack: enclomiphene (selective estrogen receptor modulator) blocks negative estrogen feedback at the pituitary to amplify FSH/LH release; gonadorelin directly stimulates gonadotropin release. Commonly combined in PCT protocols.
Gonadorelin 100 mcg SC daily + Enclomiphene 12.5 mg oral daily (PCT weeks 1–8)
Continuous GnRH receptor occupancy from long-acting agonists causes receptor downregulation and LH/FSH suppression: the opposite of gonadorelin's intended effect. Combining would be counterproductive and potentially suppressive.
Do not combineSuppress pituitary gonadotropin secretion via negative HPG feedback, directly blunting gonadorelin's LH/FSH-stimulating effect. Listed as drug interaction in FDA label.
FDA label lists digoxin as blunting gonadotropin response to gonadorelin. Mechanism unclear.
May blunt LH/FSH response to gonadorelin. Dopamine normally suppresses prolactin and modulates GnRH pulsatility; antagonists alter this balance. Listed in FDA label.
Pricing updated 2026-04-09
Paradoxical LH suppression is the most serious risk with gonadorelin. Dosing too frequently or at too high a volume (above 200 mcg per day sustained) can cause GnRH receptor desensitization. The result is the opposite of the intended effect: LH and FSH decline, testosterone drops, and testicular atrophy accelerates. This isn't a theoretical concern. It's the exact mechanism that makes leuprolide an effective prostate cancer drug. If your labs show declining LH despite consistent gonadorelin use, receptor downregulation is the likely cause. Stop dosing for 3 to 5 days to allow receptor recovery. Published side effects from the Factrel FDA label and clinical use data include headache, nausea, and lightheadedness. These are generally mild and occur most often after the first few injections. Flushing is reported within 30 minutes of injection in a subset of users. Injection site reactions (redness, swelling, minor pain) occur at rates typical for any subcutaneous peptide. Rotating injection sites between abdominal fat and thigh reduces irritation. Estradiol elevation is possible at weeks 6 to 8. As gonadorelin drives testosterone production through Leydig cells, some testosterone converts to estradiol via aromatase. Users with higher body fat or genetic aromatase activity may need an aromatase inhibitor. Monitor E2 levels if testosterone is rising and symptoms like water retention or nipple sensitivity appear. Community reports from r/trt and ExcelMale forums flag highly variable individual response as the most common complaint, not side effects per se. Many users on 2x/week protocols report zero benefit, which is a dosing frequency issue rather than a safety issue. Contraindications: hormone-dependent tumors (breast, prostate), pituitary apoplexy or known pituitary adenoma, pregnancy, and primary hypogonadism (gonadorelin stimulates the pituitary, so it won't help if the testes themselves can't respond). If you have primary hypogonadism, confirmed by raised baseline LH/FSH, this peptide is not indicated. Stop use and consult a physician if you experience severe headache, visual disturbances, or signs of pituitary apoplexy.
Verify Gonadorelin dosing and safety with a second opinion
Gonadorelin is a Category 1 bulk drug substance on the FDA 503A and 503B lists: one of the few peptides legally compoundable as of 2026. It was previously FDA-approved (Factrel, Lutrepulse) for human use. Compounded from licensed 503A/503B pharmacies with valid prescription. No quality sweeps or enforcement actions specifically targeting gonadorelin in 2024-2026.
| Test | When | Target |
|---|---|---|
| LH (post-dose response test) | Draw at 30 minutes post-injection on day 1 or week 1 | LH peak ≥2× pre-dose baseline; typical post-dose peak 4–12 mIU/mL |
| LH and FSH (baseline + follow-up) | Baseline before starting; repeat at weeks 6–8 | LH: 1.4–12.8 mIU/mL; FSH: 1.5–12.4 mIU/mL |
| Total testosterone | Baseline; weeks 6–8; then every 3 months | Goal: maintain or increase from suppressed baseline. PCT target: ≥400 ng/dL before discontinuing. |
| Estradiol (E2) | At weeks 6–8 if testosterone is rising | 20–40 pg/mL (sensitive assay) |
| Semen analysis | Baseline (if fertility is a goal); repeat at month 3–6 | — |
Confirms pituitary GnRH receptor responsiveness. An LH rise of ≥2× baseline confirms pituitary is responsive to gonadorelin. Flat response may indicate pituitary damage or inadequate dose.
Track whether pulsatile stimulation is maintaining LH/FSH levels. Also rules out primary hypogonadism if LH/FSH are elevated at baseline (indicating testes, not pituitary, are the failure point: gonadorelin will not help).
Primary efficacy marker for TRT co-admin and PCT goals. Rising endogenous T confirms Leydig cell response.
Rising testosterone increases aromatase substrate, potentially elevating E2. May require aromatase inhibitor.
Spermatogenesis depends on FSH-driven Sertoli cell support. Confirms whether gonadorelin is preserving/restoring sperm production.
Acute LH spike measurable within 15-30 minutes. No subjective effects yet.
LH and FSH levels stabilizing with consistent pulsatile dosing.
Testosterone levels start rising if pituitary-gonadal axis is intact.
Full effect on testosterone, testicular volume, and spermatogenesis measurable on labs.
Day 1, first injection: LH peaks within 15 to 30 minutes and drops back to baseline in 2 to 4 hours. FSH takes longer to respond. No subjective effects yet. Some users draw a same-day LH lab at the 30 minute mark to confirm their pituitary is responding before committing to a full protocol. Mild flushing or lightheadedness can hit within 30 minutes. Transient headache in a minority. Weeks 1 to 2: LH and FSH start stabilizing at higher basal levels with consistent pulsatile dosing. Leydig cell testosterone production activates in response. Most users don't feel anything yet. Some on nightly protocols notice slight scrotal fullness by end of week 2. Weeks 3 to 4: Endogenous testosterone starts climbing if the pituitary-to-testicular axis is intact. Some users report libido improvement and subjective testicular fullness. The 2x/week crowd often reports nothing at this point; frequency is usually the limiting factor. Weeks 6 to 8: This is where labs confirm whether the protocol is working. Testosterone, testicular volume, and sperm parameters should show maximum response. The 2025 pump trial data (n=54)[2] tracked roughly 79% spermatogenesis achievement at a median of 6.5 months. Users on nightly bolus protocols report consistent testicular size maintenance on semen analysis. Watch for estradiol creep as testosterone rises through aromatase conversion. Months 3 to 6 (fertility focus): For men using gonadorelin specifically for fertility, PMID 40119359 reported median time to first sperm at 12.3 months with pulsatile pump. Bolus injection protocols likely run slower. Most fertility-focused users transition to HCG plus FSH under a reproductive endocrinologist at this stage if gonadorelin alone isn't cutting it.
LH peaks within 15–30 minutes of injection and returns to baseline within 2–4 hours. FSH rises more slowly. This is the mechanistic proof-of-concept.
No subjective effects expected. Some users draw a same-day LH lab to confirm pituitary response before committing to protocol.
With consistent pulsatile dosing, LH and FSH levels begin stabilizing at higher basal levels. Testosterone production in Leydig cells activates in response to LH.
Minimal noticeable change yet. Some users report slight scrotal fullness beginning at the end of week 2 with nightly dosing.
Endogenous testosterone measurably increases if pituitary-to-testicular axis is intact. LH and FSH stabilize with consistent pulsatile dosing.
Some users report libido improvement and subjective testicular fullness. Variable response: 2×/week users often report nothing at this stage.
Testosterone, testicular volume (ultrasound-measurable), and sperm parameters should show maximum response at this point. 2025 pump data: ~79% of CHH patients achieve spermatogenesis at median 6.5 months.
Experienced users on nightly protocol report consistent testicular size maintenance and improved fertility markers on semen analysis.
PMID 40119359: median time to first sperm appearance was 12.3 months with pulsatile pump. Bolus injection protocols likely slower.
Men using gonadorelin for fertility typically transition to HCG + FSH under fertility specialist guidance at this point if gonadorelin alone is insufficient.
Source: Factrel FDA label; SC terminal t½ ~20-40 min (IV t½ 2-10 min, but administration is SC)
Loading the interactive decay curve.
Gonadorelin was FDA-approved in 1978 under the brand name Factrel (gonadorelin hydrochloride) for diagnostic evaluation of pituitary gonadotroph function. A separate formulation, Lutrepulse (gonadorelin acetate), was approved for pulsatile pump delivery in hypogonadotropic hypogonadism. Both brand products have been discontinued in the US market. Gonadorelin is listed as a Category 1 bulk drug substance on the FDA's 503A and 503B compounding lists. This means licensed compounding pharmacies can legally prepare it with a valid prescription. It remains one of the few peptides with clear legal compounding status after the FDA's 2023 to 2025 enforcement actions against other peptides. For athletes: gonadorelin is prohibited by WADA under the S2 category (peptide hormones, growth factors, related substances, and mimetics). Any use in sanctioned competition is a doping violation. This content is for educational and informational purposes only. It does not constitute medical advice. Consult a licensed healthcare provider before starting any peptide protocol.
Peptide Schedule Research TeamReviewed Apr 20265 Citations
