Gonadorelin common uses, half-life, side effects and more

Gonadorelin is synthetic gonadotropin-releasing hormone. It is the signal the hypothalamus sends to make the pituitary release LH and FSH. Doctors give a single dose to test whether the pituitary responds. A pump delivering small pulses every 90 minutes treats some causes of infertility. Men's health clinics now prescribe compounded gonadorelin during testosterone therapy as a substitute for hCG. That switch happened because hCG lost its compounding pathway rather than because gonadorelin worked better. Both approved US products, Factrel and Lutrepulse, are discontinued. Every product sold in the United States under the Factrel name today is for cattle.

• Pituitary function testing with a single supervised dose
• Pump therapy for infertility caused by GnRH deficiency
• Clinic use alongside testosterone therapy to keep the testes working
• Attempts at restarting the hormonal axis after anabolic steroid use

A diagnostic test is one dose. Pump therapy delivers a pulse every 90 to 120 minutes. Clinic use during testosterone therapy is usually twice weekly.

The diagnostic test uses 100 mcg once by subcutaneous or intravenous injection. That amount is the same for every adult regardless of weight. Pump therapy uses 5 to 20 mcg per pulse every 90 to 120 minutes and works out to roughly 112 doses a week. Clinics prescribe 100 mcg under the skin twice weekly for men on testosterone. Real prescriptions run from 50 mcg to 1 mg and from once weekly to daily. No clinic publishes a source for that figure. Repeated 100 mcg injections were tried as a treatment in the 1970s. Giving them three times a day still produced only below-normal testosterone. Every historical regimen that restored testicular function dosed at least three times daily or used a pump.

• Pump therapy and twice-weekly injection are different treatments and outcomes from one say nothing about the other
• Injection site changes the curve because an upper-arm dose peaks faster and higher than an abdominal one
• Kidney impairment slows clearance while liver disease does not

Gonadorelin leaves the blood fast. Human measurements put the quick disappearance phase at roughly two to six minutes. The four-minute figure on the UK label describes that phase. Injected under the skin it lingers longer and one study still found it above baseline past two hours. The later stage of clearance has never been characterized cleanly in people.

The UK diagnostic product is stored below 25 C and used within 24 hours of reconstitution. Compounded products follow the dispensing pharmacy's beyond-use date.

• Injection-site redness, swelling, pain, or bruising
• Headache, flushing, dizziness, nausea, or abdominal discomfort
• Pump-site inflammation, infection, or interrupted delivery during pulsatile therapy
• Hypersensitivity reactions including rash, wheezing, hives, and rarely anaphylaxis
• Antibody formation and a weaker response after prolonged repeated use

Gonadorelin binds the GnRH receptor on pituitary cells and triggers release of LH and a smaller rise in FSH. LH and FSH then drive the gonads to make sex steroids and to support sperm or egg development. The pituitary reads the timing of the signal rather than the amount. Natural pulses arrive roughly every 90 minutes in men. Pulses at that spacing sustain output. Continuous exposure switches the pituitary off instead. That is how related drugs are used to suppress hormones in prostate cancer. Large single doses also blunt the response for a while. One study found a second dose almost unanswered thirty minutes after the first. Whether that blunting still matters days later has never been measured.

Pump therapy has real evidence behind it. A 25-year series of 66 women reported ovulation in 96% of cycles and live birth in 66% of treatments. A meta-analysis of 35 studies covering about 1,000 women found subcutaneous and intravenous pulses comparable. Pump therapy in men with congenital GnRH deficiency induced sperm production faster than injected gonadotropins did. None of that transfers to the clinic regimen. No trial has tested whether injected gonadorelin preserves testicular function or fertility during testosterone therapy. No such trial is even registered. Two 2025 specialist reviews on preserving sperm production during testosterone therapy do not mention gonadorelin. One controlled study found testosterone treatment blunts the LH response to a GnRH dose.

• Testosterone treatment blunts the LH response to gonadorelin and the men most likely to inject it are the ones least likely to respond
• Twice-weekly injection matches no regimen that has ever been shown to restore testicular function
• WADA prohibits gonadorelin for male athletes at all times as a non-specified substance and female athletes sit outside that section only for now
• Every product sold in the United States under the Factrel name today is a cattle drug with cattle dosing
• Ovulation induction by pump can overstimulate the ovaries and lead to multiple pregnancy or cyst rupture
• Compounded gonadorelin is dispensed against a prescription and anything sold as a research chemical sits outside that framework