Gonadorelin has a dose record with an unusual shape. The amounts in it are small and consistent — single-digit to low-double-digit micrograms. What varies, and what almost nothing written about this compound carries, is the interval, and the interval is the part that decides whether the molecule switches the pituitary on or off.
Before that, a fact about the label situation that is easy to get wrong in the other direction.
There is no current US human label for this molecule
Both US human products are discontinued. From Drugs@FDA, read on 21 September 2026:
| Application | Brand | Sponsor | Strengths | Marketing status |
|---|---|---|---|---|
| NDA 018123 | FACTREL | Hikma | 0.1 mg, 0.2 mg, 0.5 mg per vial | Discontinued |
| NDA 019687 | LUTREPULSE KIT | Ferring | 0.8 mg, 3.2 mg per vial | Discontinued |
The approvals are still in the database. The products are not on the market. Those are two different statements, and a page that cites "an FDA-approved drug" without checking the second one is describing a filing cabinet rather than a pharmacy.
Every current US gonadorelin label is a cattle label
A DailyMed search for gonadorelin on the same date returns five current labels:
| Label | Holder | Species |
|---|---|---|
| FACTREL Injection | Zoetis | Cattle |
| GONABREED | Parnell Technologies | Cattle |
| CYSTORELIN | Boehringer Ingelheim Animal Health | Cattle |
| FERTAGYL | Merck Animal Health | Cattle |
| OVACYST | Bimeda | Cattle |
All five. The brand name FACTREL now belongs to a Zoetis product for dairy cows, which is why a search for the historic human brand lands on a livestock label without anything on the page announcing the change.
The CYSTORELIN warnings section reads, in its entirety:
Not for use in humans.
So the only currently labelled doses of gonadorelin in the United States are these:
| Product | Indication | Dose |
|---|---|---|
| CYSTORELIN | Cystic ovaries, lactating dairy and beef cows | 100 μg (2 mL) per cow, intravenous or intramuscular |
| CYSTORELIN | Reproductive synchrony, with cloprostenol | 100 μg per cow IM at Day 0, second dose 30–72 h after the cloprostenol injection |
| FACTREL | Ovarian follicular cysts | 2 mL as a single intramuscular injection |
| FACTREL | Fixed-time AI with dinoprost | 100–200 μg (2–4 mL) per cow IM, two doses 6–8 days apart around the prostaglandin |
These are real doses in a real regulatory document, and they establish nothing about a person.
The human record: micrograms per pulse, by pump
The human literature is not a label literature. It is a small set of endocrinology trials, and in all of them the delivery device is part of the dose.
| Source | Population | Dose | Interval | Route |
|---|---|---|---|---|
| J Clin Endocrinol Metab 2015;100(7):2793–9 (PMID 25978110) | 12 adolescent boys with hypogonadotropic hypogonadism | 8–10 μg | every 90 min | subcutaneous, pump |
| Eur J Endocrinol 1994;131(4):347–54 (PMID 7921222) | men | 5–20 μg | every 120 min | subcutaneous |
| Lancet 1987;2(8558):552–5 (PMID 2887840) | girls and boys with delayed puberty | 1–2 μg (girls), 2–4 μg (boys) per pulse | — | — |
| Fertil Steril 1985;43(4):599–608 (PMID 3921412) | boys with idiopathic delayed puberty | 25 μg IV test dose; then 2 μg | every 2½ h | subcutaneous |
| J Clin Endocrinol Metab 1984;59(4):739–46 (PMID 6384253) | 14 hypogonadotropic patients | 5 μg bolus; 3.17 μg/h infusion | — | SC and IV compared |
The 2015 trial is the most recent and the most complete. Twelve patients at Beijing Children's Hospital received 8–10 μg of gonadotropin-releasing hormone subcutaneously every 90 minutes using a pump, for 12 to 14 months, alongside 22 patients on intramuscular human chorionic gonadotropin. The gonadorelin arm showed larger testicular volume; testosterone and penile length did not differ significantly between the arms.
Note what the dose figure is attached to in every row: a pump, a schedule, and a duration measured in months.
The interval is the pharmacology
This is the part worth being precise about, because it inverts.
Pulsatile gonadotropin-releasing hormone stimulates the pituitary to release luteinising hormone and follicle-stimulating hormone. A continuous stimulus at the same receptor desensitises it and blocks that release.
Kumar and Sharma, J Hum Reprod Sci 2014;7(3):170–4, state it in exactly those terms: pituitary stimulation with pulsatile GnRH induces both FSH and LH, and pituitary gonadotropin secretions are blocked upon desensitisation when a continuous GnRH stimulus is provided.
That mechanism is not a footnote. It is the entire basis of the GnRH-agonist class — the drugs given precisely to shut down sex-hormone production, which achieve it by delivering the same signalling molecule without the gaps. The molecule does not change. The schedule does.
So a gonadorelin figure quoted without its interval has lost the variable that determines the direction of the effect. A microgram number on its own is not a dose for this compound in the way it is for most of the compounds on this site's dosage chart — it is half of one.
Route changes the curve, and that was measured
Handelsman and colleagues ran the comparison in 1984 because pulsatile treatment was producing deficient responses by the subcutaneous route in contrast to the intravenous route, and nobody knew whether bioavailability alone explained it.
Fourteen hypogonadotropic patients, 5 μg boluses:
| Intravenous | Subcutaneous | |
|---|---|---|
| Peak plasma IR-GnRH | 400 pg/mL | 93.5 pg/mL |
| Return to baseline | < 60 min | > 120 min |
The subcutaneous route produced a lower, later, flatter curve — lower between 1 and 5 minutes, higher between 30 and 90 minutes. For a hormone whose effect depends on the pituitary seeing a sharp pulse followed by a gap, a flattened curve is not a smaller dose of the same thing.
What the record does not contain
No study in this site's sources administered gonadorelin to healthy adults on a once- or twice-weekly schedule. The human trials are in people with a specific hypothalamic defect, dosed around the clock by pump for months, with an endpoint — puberty, testicular volume, ovulation — that the deficiency itself defines.
The half-life chart carries this compound with the same caveat, and how to read a dosing claim sets out why a figure detached from its schedule and population is not a transferable number. The comparison this compound is most often set against, human chorionic gonadotropin, has its own record on this site's HCG dosage page, and it is a genuinely different document: an approved drug with a current human label.
Method
Drugs@FDA was queried through the openFDA API on 21 September 2026 for application numbers NDA 018123 and NDA 019687 and for products matching the brand names FACTREL and LUTREPULSE; marketing status is quoted from the product records returned. The DailyMed SPL service was queried the same day for drug_name=gonadorelin; five labels were returned and each title is reproduced above with its holder. The CYSTORELIN and FACTREL veterinary dose and warning text is quoted from those labels directly. Every human figure is cited to the paper it was read from by PMID, journal, volume and page, and each abstract was opened rather than taken from a result list. Nothing on this page is a dosing instruction.