Equine Chorionic Gonadotropin
The placental hormone of pregnant mares, how farms use it to time breeding in cattle, pigs and sheep, and why it has no place in human medicine
Equine chorionic gonadotropin (eCG), long called pregnant mare serum gonadotropin (PMSG), is a hormone made by the placenta of pregnant horses. In horses it acts like luteinizing hormone, but in cattle, pigs, sheep and laboratory mice it acts like both follicle-stimulating and luteinizing hormone, so a single injection drives follicle growth and ovulation. That makes it a cheap, widely used veterinary drug for timing breeding. It is extracted from the blood of pregnant mares, which has raised welfare concerns. It is approved only for animals, and no human use was found in the literature read.
No established human dose Details ↓
Recommended Dosing
No established human dose
No human dose exists for eCG. It is approved only for animals, and every trial read here was done in cattle, pigs or mice, with the amounts chosen for those species.
What is it?
Only primates and horses are known to make a chorionic gonadotropin, a pregnancy hormone from the placenta. In the mare, cells from a band of the early placenta called the chorionic girdle invade the lining of the womb at about day 36 to 37 of pregnancy and form the endometrial cups. These cups secrete equine chorionic gonadotropin into the mare's blood, where it peaks at around two months of pregnancy and disappears by about day 130. Because it was first found in mares' blood, it was called pregnant mare serum gonadotropin (PMSG); eCG is the name now preferred, since the hormone comes from the placenta.
Structurally eCG is a two-chain glycoprotein. Its alpha chain is shared with the horse's pituitary hormones and its beta chain has the same amino-acid sequence as horse luteinizing hormone (LH). It carries more sugar than any other known hormone of its family, and its sialic-acid content gives it an exceptionally long life in the circulation. In the mare it acts on LH receptors and is thought to support extra corpora lutea, the progesterone-making structures that sustain early pregnancy. Mares carrying mule foals make far less eCG, and in one study their corpora lutea were less protected against a drug that ends them.
The feature that matters to farmers is what eCG does outside the horse. In cattle, sheep, goats, pigs and rodents it binds both follicle-stimulating hormone (FSH) and LH receptors, so one long-acting injection grows follicles and supports ovulation and the corpus luteum that follows. Veterinary practice uses it to bring animals that are not cycling into heat, to tighten the timing of ovulation for fixed-time artificial insemination, and in larger amounts to make cows release many eggs at once (superovulation). Laboratories use it in the same way to superovulate mice for making transgenic animals.
The cattle trials show a consistent pattern. eCG helps most where the animal's own LH drive is weak: cows that are not cycling, cows soon after calving, thin cows and suckled beef cows. In those groups, randomised trials found higher heat rates, larger follicles and more pregnancies per insemination. In cows that are already cycling well the benefit shrinks or disappears, and a 2023 review of dairy trials judged the evidence inconsistent. Higher amounts raise the chance of double ovulation and twins, which carry more pregnancy losses.
Making eCG means bleeding pregnant mares, which has drawn criticism after reports of injuries and deaths on some South American farms. Reviews describe no fully satisfactory replacement, although recombinant eCG has now been tested in cattle and researchers have grown placental organoids that secrete it. For people, eCG is not a medicine: it is approved only for animals, and human medicine uses hCG, collected from the urine of pregnant women, as its LH-like placental hormone.
Mechanism of Action
eCG is a two-chain glycoprotein hormone that, outside the horse, binds both FSH and LH receptors on the ovary and lasts a long time in the blood, so one injection grows follicles and supports ovulation and the corpus luteum.
FSH-like action
In cattle, sheep, pigs and mice it drives follicle recruitment and growth, the basis of its use in breeding programmes and superovulation (PMIDs 2026120, 24456154).
LH-like action
It supports ovulation and the corpus luteum that follows, raising progesterone; in the mare itself it acts only on LH receptors (PMIDs 33080658, 24617452).
Long-lasting
Heavy glycosylation with sialic acid gives it an exceptionally long half-life compared with other glycoprotein hormones (PMID 2026120).
Published Research
These studies were read from their PubMed abstracts on October 29, 2026. They are veterinary reviews and trials in cattle and pigs, studies of eCG production in mares, and laboratory work. They are labelled by species; none was carried out in people.
What eCG is and where it comes from
A review of horse chorionic gonadotropin: made by the endometrial cups from about day 36 of pregnancy and detectable until about day 130, built from a 96-residue alpha chain and a 149-residue beta chain identical to horse LH beta, the most heavily glycosylated hormone of its family, with a very long half-life and both FSH and LH activity in species other than the horse.
The equine placenta and its hormone
An overview of how the endometrial cups form when girdle cells invade the womb lining around day 37, why eCG is the better name than PMSG, and how secretion peaks between days 60 and 80 with wide variation between mares and no known hormonal control.
Biology and veterinary use
A German review explains why eCG became a comparatively cheap FSH substitute in ruminants and pigs, and notes that unlike hCG, which is collected from the urine of pregnant women, eCG must be taken from mares' blood; reports of mare deaths in South America have led to calls for a production ban.
eCG in dairy cow reproduction
A review describes eCG's long-lasting FSH- and LH-like effects in cattle: fewer atretic follicles, better growth of the dominant follicle, a better corpus luteum and more progesterone. The benefits are clearest when LH secretion is low, as after calving, in heat stress, in non-cycling cows or in thin cows.
Dairy trials give inconsistent results
A rapid review of 15 dairy-cow studies could not pool them in a full meta-analysis. Most added eCG to progesterone-based synchronisation programmes; results for conception were mixed, with most confidence intervals crossing no effect, and the authors call for larger, better-designed trials.
Welfare of the mares bled for eCG
A review of how eCG is collected from mares between days 40 and 120 of pregnancy. Bleeding too often or too much, rough handling of mares kept on open range and minimal veterinary oversight can cause serious injury and death; the authors set out recommendations to protect them.
Timing the injection in anestrous beef cows
In lactating beef cows that were not cycling, giving eCG two days before removing a progestin device, rather than on the day of removal, gave larger follicles, bigger corpora lutea, more progesterone and a higher pregnancy rate after fixed-time insemination (27.3% versus 16.0% in 246 cows).
More pregnancies in suckled beef cows
In 966 suckled beef cows, adding eCG at progesterone-device removal raised the heat rate and pregnancies per insemination (about 30% without eCG, 45-48% with it) and gave larger follicles; the two amounts tested worked equally well.
Helps early after calving only
In 679 grazing crossbred dairy cows, eCG tended to raise pregnancies per insemination overall and clearly raised them in cows bred within 70 days of calving, with no effect later; twinning and losses did not differ.
Higher amounts, more twins
In 2,382 Angus heifers randomised to two eCG amounts, pregnancy rates were the same, but the higher amount caused more double ovulations and twins; heifers carrying twins lost more pregnancies than those carrying one calf.
Recombinant eCG in beef cattle
Across three experiments in about 2,400 suckled beef cows, recombinant eCG raised heat rates and pregnancies per insemination over no treatment; in Bos indicus cows the lowest amount matched serum-derived eCG and a higher amount did worse.
Pretreatment in replacement gilts
In 166 young sows-to-be on a fixed-time insemination programme that already used eCG, an extra eCG injection 15 days earlier gave the most synchronised ovulation and the highest pregnancy and farrowing rates.
Superovulating mice for transgenic work
In mice superovulated to make transgenic animals, PMSG and human menopausal gonadotropin gave similar embryo yields and quality, but only PMSG-derived injected embryos went on to produce transgenic pups.
What sets a mare's eCG output
Across 61 pregnancies in 25 Thoroughbred mares, eCG peaked at about 62 days after ovulation and was gone by about day 134. Moderately fed mares made more than overfed ones, and by a third pregnancy it disappeared earlier.
The mare, not the stallion, sets the level
Breeding trials across several seasons found that a mare's own eCG concentration ranking held from one pregnancy to the next whatever sire she was bred to, so the mare is the main influence on how much eCG is made.
eCG protects the corpus luteum in pregnant mares
Mares carrying horse foals had about ten times more eCG than mares carrying mule foals; under repeated doses of a luteolytic prostaglandin, higher eCG was linked to slower luteal breakdown and less fetal loss.
Placental organoids that make eCG
Organoids grown from the mare's chorionic girdle secreted eCG for up to six weeks in culture, a possible route to studying, and perhaps one day producing, the hormone without repeated bleeding of pregnant mares.
Mapping eCG with antibodies
Three monoclonal antibodies against eCG recognised folded sites on its alpha and beta chains; one bound near the receptor-binding region and blocked eCG from binding LH and FSH receptors.
No Established Human Dose
No human dose exists for eCG. It is approved only for animals, and every trial read here was done in cattle, pigs or mice, with the amounts chosen for those species. No study of giving eCG to people was found, so the veterinary amounts on the label and in these trials are not shown here, and none of them applies to a person.
What this rests on: PMID 23510789, PMID 26577752, PMID 38914033, PMID 17420039.
Educational information, not medical advice. The doses on this page come from approved labels, published studies and, where no study exists, amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
What a Buyer Needs to Know
What is sold, how it is mixed, stored and taken, and what is known about its safety, quality and legal status. Each part names its source. Where we have none, it says unknown.
What is sold
No product is approved for people. The approved veterinary product, as its US veterinary label describes it:
- P.G. 600 (serum gonadotropin and chorionic gonadotropin kit) (veterinary): One vial containing white freeze‑dried powder, and one vial containing sterile diluent. When reconstituted, the five‑dose vial (25 mL) of P.G. 600 contains: SERUM GONADOTROPIN (PMSG) 2,000 INTERNATIONAL UNITS CHORIONIC GONADOTROPIN (HCG) 1,000 INTERNATIONAL UNITS (equivalent to 1,000 USP Units chorionic gonadotropin).
Source: P.G. 600 (serum gonadotropin and chorionic gonadotropin kit) veterinary label, How Supplied (DailyMed version 11, effective August 20, 2026).
Mixing a vial: a worked example
Unknown: no human dose of Equine Chorionic Gonadotropin has been established (see No Established Human Dose below), so there is no amount to work out. The reconstitution calculator does the arithmetic for any vial, water and dose.
Storage before and after mixing
No product of Equine Chorionic Gonadotropin is approved for people. The US veterinary label of the approved animal product says how it is stored:
P.G. 600 (serum gonadotropin and chorionic gonadotropin kit) (veterinary): “Store at 2‑8°C (36‑46°F).” “Once reconstituted, P.G. 600 (serum gonadotropin and chorionic gonadotropin for injection) should be used immediately.” “Unused solution should be disposed of properly and not stored for future use.”
These describe the veterinary product in its own container, not a vial sold for people. The mixing guide sets out the general rules for a mixed vial, with their sources.
Source: P.G. 600 (serum gonadotropin and chorionic gonadotropin kit) veterinary label, storage section (DailyMed version 11, effective August 20, 2026).
How it is taken
Unknown: with no established human dose, there is no established way of taking Equine Chorionic Gonadotropin. What the human studies gave and how is set out under No Established Human Dose.
What to expect, and when
Unknown: no cited half-life and no label or trial duration on this page says how long Equine Chorionic Gonadotropin lasts or how long it was given. Results reported in the studies are under Published Research.
Side effects, and when to stop or get help
From the Side Effects section: Double ovulation and twins at higher amounts in heifers, with more pregnancy losses in twin pregnancies (PMID 38914033); In Bos indicus cows a higher amount of recombinant eCG lowered pregnancies per insemination (PMID 39029411); Injury and death of donor mares where blood collection is poorly managed (PMIDs 31805698, 33080658). Full list and cautions ↓
When to stop or get help: unknown; no label or trial on file sets rules for stopping Equine Chorionic Gonadotropin. Treat a severe or unexpected reaction as a reason to stop and see a doctor.
Source: the Side Effects section below (“Reported in animals; no human safety data were found”).
Interactions
Unknown: a PubMed search for human interaction studies of Equine Chorionic Gonadotropin (reviewed 2026-10-28) found none. Unknown is not the same as safe to combine.
Every peptide's record, with its source: the interaction matrix.
Checking what you bought
Unknown: no published independent test of Equine Chorionic Gonadotropin products is in our lab-results database yet, so how products sold under this name measure up is not known.
To read a certificate of analysis, paste it into the COA decoder. Trust & Verification explains what independent testing can and cannot show.
Legal status
US: Veterinary Only (Approved only for animals). Sport: Prohibited in males, at all times (S2.2.1).
Country by country ↓ · Regulatory tracker
Source: this entry's approval status and the WADA Prohibited List, as in Legal Status below.
Side Effects & Contraindications
Reported Side Effects
Reported in animals; no human safety data were found.
Contraindications & Cautions
For people, the main point is that eCG is not a human medicine.
Legal Status
eCG is a veterinary medicine. No human approval was found.
Frequently Asked Questions
?What is eCG?
Equine chorionic gonadotropin, a glycoprotein hormone made by the placenta of pregnant mares. It used to be called pregnant mare serum gonadotropin (PMSG).
?Is eCG used in people?
No. It is approved only for animals, and no study giving it to people was found in the literature read.
?Why do farmers use it?
Outside the horse it acts like both FSH and LH and lasts a long time, so one injection can bring cows, sows or ewes into heat, time ovulation for fixed-time insemination, or make a cow release many eggs at once.
?Does it work in cattle?
Best in animals with weak cycles: non-cycling, recently calved, suckled or thin cows. Trials there found more pregnancies per insemination; in well-cycling dairy cows a 2023 review found the results inconsistent.
?Is eCG the same as hCG?
No. Both are placental gonadotropins, but hCG is the human hormone, collected from pregnant women's urine, while eCG comes from the blood of pregnant mares and has strong FSH-like activity in other species.
?Why is eCG production controversial?
It is collected by bleeding pregnant mares. Reviews describe injuries and deaths where collection is poorly managed and calls for a production ban; recombinant eCG and placental organoids are being studied as alternatives.
?How long does eCG last in the body?
Reviews describe its half-life as exceptionally long for a glycoprotein hormone because of its sialic-acid content; no figure is given in the abstracts read.
References
- [fda-pi] P.G. 600 (serum gonadotropin and chorionic gonadotropin), US FDA-approved veterinary label (description, indications and dosage; DailyMed set 8e3e54e8, version 11, effective August 20, 2026; read October 28, 2026).
- [other] US FDA Center for Veterinary Medicine, Approved Animal Drug Products (Green Book), Section 2 active-ingredient list downloaded from Animal Drugs @ FDA, read October 28, 2026: NADA 140-856, P.G. 600, active ingredients chorionic gonadotropin and serum gonadotropin. https://animaldrugsatfda.fda.gov/adafda/views/#/search
- [other] UK Veterinary Medicines Directorate, Product Information Database, currently authorised products searched by active substance, read October 28, 2026: Fixplan 200 IU/ml, VM 54400/4001, active substance serum gonadotrophin, target species cattle, pigs and sheep. https://www.vmd.defra.gov.uk/ProductInformationDatabase/
- [pubmed] Murphy BD, et al. "Equine chorionic gonadotropin." Endocr Rev, 1991;12(1):27-44. PMID: 2026120.
- [pubmed] Hoppen HO. "The equine placenta and equine chorionic gonadotrophin--an overview." Exp Clin Endocrinol, 1994;102(3):235-43. PMID: 7995345.
- [pubmed] Schuler G. "[Equine chorionic gonadotrophin: Biology and veterinary use]." Tierarztl Prax Ausg G Grosstiere Nutztiere, 2020;48(5):344-354. PMID: 33080658.
- [pubmed] De Rensis F, et al. "Use of equine chorionic gonadotropin to control reproduction of the dairy cow: a review." Reprod Domest Anim, 2014;49(2):177-82. PMID: 24456154.
- [pubmed] Beasley LH, et al. "Use of equine chorionic gonadotropin in lactating dairy cattle: a rapid review." N Z Vet J, 2023;71(2):53-64. PMID: 36265863.
- [pubmed] Manteca Vilanova X, et al. "Horse Welfare During Equine Chorionic Gonadotropin (eCG) Production." Animals (Basel), 2019;9(12). PMID: 31805698.
- [pubmed] Dorneles Tortorella R, et al. "The effect of equine chorionic gonadotropin on follicular size, luteal volume, circulating progesterone concentrations, and pregnancy rates in anestrous beef cows treated with a novel fixed-time artificial insemination protocol." Theriogenology, 2013;79(8):1204-9. PMID: 23510789.
- [pubmed] Pessoa GA, et al. "Different doses of equine chorionic gonadotropin on ovarian follicular growth and pregnancy rate of suckled Bos taurus beef cows subjected to timed artificial insemination protocol." Theriogenology, 2016;85(5):792-799. PMID: 26577752.
- [pubmed] Prata AB, et al. "Equine chorionic gonadotropin increases fertility of grazing dairy cows that receive fixed-time artificial insemination in the early but not later postpartum period." Theriogenology, 2017;98:36-40. PMID: 28601153.
- [pubmed] Cuadro F, et al. "Equine chorionic gonadotropin (eCG) treatment in heifers: Double ovulation, twinning rate, and pregnancy losses in twin pregnancies." Theriogenology, 2024;226:213-218. PMID: 38914033.
- [pubmed] Cattaneo L, et al. "The use of a recombinant equine chorionic gonadotropin (reCG) in fixed-time AI programs in beef cattle." Theriogenology, 2024;227:77-83. PMID: 39029411.
- [pubmed] Zhao Q, et al. "Equine chorionic gonadotropin pretreatment 15 days before fixed-time artificial insemination improves the reproductive performance of replacement gilts." Animal, 2021;15(12):100406. PMID: 34844186.
- [pubmed] Brooke DA, et al. "Human menopausal and pregnant mare serum gonadotrophins in murine superovulation regimens for transgenic applications." Theriogenology, 2007;67(8):1409-13. PMID: 17420039.
- [pubmed] Wilsher S, et al. "Factors influencing equine chorionic gonadotrophin production in the mare." Equine Vet J, 2011;43(4):430-8. PMID: 21496079.
- [pubmed] Martinuk SD, et al. "Effects of the dam on equine chorionic gonadotropin concentrations during pregnancy." Domest Anim Endocrinol, 1990;7(4):551-7. PMID: 2261764.
- [pubmed] Flores-Flores G, et al. "Luteoprotective role of equine chorionic gonadotropin (eCG) during pregnancy in the mare." Reprod Domest Anim, 2014;49(3):420-6. PMID: 24617452.
- [pubmed] Thompson RE, et al. "Production of Mare Chorionic Girdle Organoids That Secrete Equine Chorionic Gonadotropin." Int J Mol Sci, 2023;24(11). PMID: 37298490.
- [pubmed] Maurel MC, et al. "Immunochemical study of equine chorionic gonadotropin (eCG/PMSG): antigenic determinants on alpha- and beta-subunits." Biochim Biophys Acta, 1992;1159(1):74-80. PMID: 1382612.
Sources & Citations
Every study on this page was read from its PubMed record on October 29, 2026. Approval status comes from the FDA Green Book and the DailyMed veterinary label, and from the UK Veterinary Medicines Directorate, read October 28, 2026. Grey Peptides sells nothing and links to no vendor.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.