HCG
Gonadotropin
Human chorionic gonadotropin, a glycoprotein hormone studied in reproductive-endocrinology research.
Also referenced as: Human Chorionic Gonadotropin
Overview
Human chorionic gonadotropin (HCG) is a glycoprotein hormone produced by the placenta during pregnancy. Pharmaceutical HCG is obtained from the urine of pregnant women or produced by recombinant technology (choriogonadotropin alfa).
At a glance
What HCG does
Human chorionic gonadotropin (hCG) is a placental glycoprotein hormone whose peptide research use hinges on one property: it is an LH mimetic. hCG binds the same luteinizing-hormone receptor (LHCGR) found on testicular Leydig cells and on ovarian theca and granulosa/luteal cells, so functionally it does what an LH pulse does — but with a much longer half-life, giving a more sustained stimulus. It therefore acts at the gonadal end of the HPG axis, bypassing the hypothalamus and pituitary entirely.
On Leydig cells, hCG activates the LH/CG receptor and triggers a cAMP–PKA signaling cascade that upregulates steroidogenic enzymes and drives testosterone synthesis; studies comparing LH and hCG in Leydig cells show they engage early signaling somewhat differently but ultimately produce equivalent testosterone output. In men this is used to raise endogenous testosterone and to maintain testicular size, intratesticular testosterone, and spermatogenesis — for instance in hypogonadotropic hypogonadism or to preserve fertility. In women, a bolus of hCG mimics the mid-cycle LH surge and is the classic ovulation 'trigger,' inducing final oocyte maturation and rupture of the mature follicle, and it also supports the corpus luteum.
Because it acts directly on the gonad rather than suppressing the axis, hCG is used where LH-like activity is needed. Its LH-mimetic gonadal actions are well established in human clinical practice.
Effects reported in research
- Binds the LH/CG receptor (LHCGR) on Leydig cells and drives cAMP-PKA signaling and testosterone synthesis (human and in-vitro).
- Maintains testicular size, intratesticular testosterone, and spermatogenesis in men, including during exogenous-androgen use or hypogonadotropic hypogonadism (human clinical use).
- Acts as an ovulation trigger, mimicking the mid-cycle LH surge to induce final oocyte maturation and follicle rupture (human clinical use).
- Supports the corpus luteum and progesterone production after ovulation (human clinical use).
- Provides a longer-lasting LH-like stimulus than native LH owing to its extended half-life (human pharmacokinetics).
- Produces testosterone output equivalent to LH in Leydig cells despite differing early signaling kinetics (in-vitro comparison studies).
- Used to stimulate testosterone secretion when pulsatile GnRH is not indicated, as a direct source of LH bioactivity (human clinical use).
Effects listed reflect findings reported in the research literature — many in animal or in-vitro models. Listing an effect is not a claim of efficacy or a therapeutic indication in humans.
Mechanism of action
HCG is a heterodimeric glycoprotein consisting of an alpha subunit (shared with LH, FSH, TSH) and a hormone-specific beta subunit. It acts as an agonist at the luteinizing hormone/choriogonadotropin receptor (LHCGR), thereby mimicking LH activity. In the gonads this stimulates testicular Leydig cells to produce testosterone and supports ovarian steroidogenesis and ovulation, which underlies its clinical use in fertility and endocrine medicine.
Mechanistic description reflects published research-literature understanding. Much peptide research is preclinical (in-vitro or animal-model); mechanism in humans may differ and is not established for many compounds.
What it's studied for
Research contexts in which HCG appears in the literature. Listing a research area is not a claim of efficacy or a therapeutic indication.
Key characteristics
- Glycoprotein heterodimer with alpha and beta subunits.
- Acts as an LH mimic at the LHCGR receptor.
- Stimulates gonadal steroidogenesis (e.g., testosterone, ovarian hormones).
- Available as urinary-derived and recombinant (choriogonadotropin alfa) products.
- An approved drug in fertility and endocrine medicine.
Reported research dosing reference only
Educational reference, not dosing guidance. The figures below summarize amounts reported in published research and research-community protocols, provided for educational and research context only. They are not medical advice, not a recommendation, and not instructions for human use. HCG is a research compound.
Reference figures only, expressed in international units (IU) as HCG is a glycoprotein. Male-model research commonly references intermittent subcutaneous/intramuscular administration.
- Male HPG-axis research: ~500-2500 IU, 2-3 times weekly (commonly referenced)
- Higher-dose references: up to ~1000-4000 IU up to 3 times weekly
- Female ovulatory-trigger research: single larger IU doses (e.g. ~5000-10000 IU referenced)
Long ~30 h half-life with peak testosterone response ~72-96 h post-dose informs weekly spacing. Reference figures for research context only.
How it compares
HCG acts directly at the gonadal LHCGR as an LH mimic, unlike GnRH analogs (gonadorelin/triptorelin) that act at the pituitary or kisspeptin acting on GnRH neurons.
Commonly studied alongside
Compounds frequently researched together with HCG in the literature. Cross-referenced for research context — not a usage or combination recommendation.
Handling & Stability
Lyophilized peptides are stored cold, protected from light, and reconstituted only at the time of intended in-vitro work.
- Avoid repeated freeze-thaw cycles
- Verify supplier lot and Certificate of Analysis
- Follow institutional lab-safety protocols
Analytical & COA Concepts
Reputable research suppliers publish a third-party Certificate of Analysis per batch. Key analytical concepts referenced in COAs include:
Category Context
HCG sits in the Hormonal & Sexual Health area of the PeptiDex library.
- Entry type: Research compound reference
- Browse the full library →
- Glossary of terms →
Where researchers source HCG
For researchers studying HCG, third-party suppliers such as Practically Natty Peptides offer research-grade material with third-party Certificates of Analysis and US-based shipping.
View research-supplier listing →
Outbound link to a third-party research supplier. Inclusion does not constitute endorsement; all editorial content is developed independently.
Frequently asked questions
What is HCG?
HCG (human chorionic gonadotropin) is a glycoprotein hormone that shares its alpha subunit with LH, FSH and TSH and binds the LH/hCG receptor with high affinity. Because it mimics luteinizing hormone at the gonad, it is studied as a direct gonadotropic stimulus of Leydig-cell (testosterone) and ovarian function.
What is HCG studied for in HPG-axis research?
In male models it is studied for stimulating Leydig-cell activity and intratesticular testosterone, and in axis-recovery research following exogenous androgen suppression. In female reproductive research it is studied as an ovulatory trigger. It is a regulated pharmaceutical hormone, not an approved research-chemical use.
Why does HCG have a much longer duration than LH?
HCG's terminal half-life is roughly 30 hours versus about 30 minutes for LH, owing to its heavier glycosylation and slower clearance. Because of this, peak testosterone responses in studies are typically seen ~72-96 hours after a dose, which shapes dosing intervals in research protocols.
How does HCG differ from gonadorelin in research use?
Gonadorelin acts upstream at the pituitary GnRH receptor to drive endogenous LH/FSH, whereas HCG bypasses the pituitary and acts directly at the gonadal LH receptor. Researchers choose between them depending on which part of the HPG axis they want to stimulate or test.
Is HCG a peptide?
HCG is a large glycoprotein hormone, not a small synthetic peptide, so it has no simple one-letter amino-acid sequence and is quantified in international units (IU) rather than by mass. This is why research dosing is expressed in IU.
Answers are educational summaries of research-literature context and do not constitute medical advice. See the Research Library, COA guide, and Storage & Handling guide for more.