Gonadorelin
Gonadorelin is a synthetic **hypothalamic hormone** (GnRH analogue) used primarily in veterinary medicine to treat reproductive disorders such as ovarian follicular cysts, particularly in dairy cattle. Key highlights: - **Very short duration of action** (minutes). - Used off-label in small animals for diagnostic purposes (e.g., differentiating castrated vs. intact animals, identifying retained testicles) and to induce estrus or ovulation. - **No slaughter or milk withdrawal** required when used as labeled in food animals. - Highly safe with virtually no reported adverse effects.
Mechanism: Gonadorelin acts as a synthetic **GnRH** (Gonadotropin-Releasing Hormone) โ binds to receptors on the anterior pituitary gland โ stimulates a surge-like release of **FSH** (Follicle Stimulating Hormone) and **LH** (Luteinizing Hormone). - In females (cows, ewes, cats), this LH surge can induce ovulation or luteinization of cystic follicles. - In males, it stimulates testosterone release, which is useful for diagnostic stimulation testing. - Note: A constant infusion initially stimulates LH/FSH release, but eventually causes receptor downregulation and levels return to baseline.
Dosing by species
- To induce ovulation outside of the breeding season ยท 100 micrograms injected daily ยท Injection ยท q24h ยท 4-5 days
- To induce ovulation outside of the breeding season in the doe ยท 100 micrograms injected daily ยท Injection ยท q24h ยท 4-5 days
- To stimulate ovulation after mating ยท 25 micrograms IM after mating ยท IM ยท Once
- For infertility, reduced libido, testis descent in male cats ยท 1 microgram/kg every 2-3 days ยท IM ยท q48-72h
- To detect ovarian remnants in queens after ovariohysterectomy ยท 25 micrograms per cat ยท IM ยท Once ยท Progesterone level (>1 ng/mL) 1-2 weeks post treatment verifies presence of ovarian tissue.
- To induce ovulation ยท 20 micrograms IM ยท IM ยท Once ยท Repeat in one week as necessary ยท Most effective 14 days after onset of estrus.
- To treat ovarian cysts in cattle ยท 100 micrograms IM or IV ยท IM/IV ยท Once
- To treat ovarian cysts in cattle ยท 100 micrograms IM per cow ยท IM ยท Once
Routes of administration
Contraindications
- None noted on the label
Adverse effects
- None reported
- Hypersensitivity reactions are highly unlikely with synthetic preparations
Monitoring
- Clinical efficacy (e.g., resolution of cystic ovaries, induction of estrus)
- Serum progesterone levels (for ovarian remnant or cystic ovary verification)
- Serum testosterone levels (for cryptorchidism/castration testing)
Overdose
In doses of up to 120 micrograms/kg, no untoward effects were noted in several species of test animals. Gonadorelin is unlikely to cause significant adverse effects after inadvertent overdosage.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturerโs current label.