HCG (Human Chorionic Gonadotropin)
Gonadotropin Hormone | LH Receptor Agonist
On this page
What is HCG (Human Chorionic Gonadotropin)?
HCG (human chorionic gonadotropin) is a hormone the body naturally produces during pregnancy, and pharmaceutical HCG is manufactured for research and approved clinical uses through the same hormone pathway. Researchers study how it activates LH receptors — the same receptors luteinizing hormone acts on — in reproductive-endocrine research. Research-grade HCG sold here is intended strictly for laboratory research use, not for self-administration in people or animals.
Key terms:
HCG (Human Chorionic Gonadotropin) is a heterodimeric glycoprotein with two non-covalently linked subunits.
Human Chorionic Gonadotropin (HCG) is a glycoprotein hormone — a protein with sugar chains attached. The placenta makes it naturally during pregnancy. It has two subunits. The alpha subunit is identical to the one in other pituitary hormones (LH, FSH, TSH). The unique beta subunit gives HCG its specific biological activity. Pharmaceutical HCG is derived from the urine of pregnant women, or produced recombinantly in engineered cells. It binds to and activates LH receptors, which is why medicine applies it in hypogonadism, infertility, and cryptorchidism (undescended testicles). In TRT protocols, HCG is commonly used to maintain testicular function, preserve fertility, and limit testicular shrinkage (atrophy).
Key research areas
- Maintains testicular function during TRT
- Preserves fertility
- Prevents testicular atrophy
- Stimulates endogenous testosterone production
- Induces ovulation in women
- Treats cryptorchidism in children
Researched dosing
This table reflects how researchers and clinicians have structured HCG study and treatment protocols in the literature — presented as reference data, not personal dosing guidance.
| Phase | Dose | Frequency | Route |
|---|---|---|---|
| TRT-adjunct studies (low dose) | 250-500 IU | Every other day | SubQ or IM |
| TRT-adjunct studies (standard) | 500-1000 IU | Twice weekly | SubQ or IM |
| Single-agent hypogonadism studies | 1500-2000 IU | 2-3 times weekly | IM injection |
| Fertility studies (with FSH) | 1500-2000 IU | 2-3 times weekly | IM injection |
| Cryptorchidism studies (pediatric) | 1000-5000 IU (age-dependent) | 2-3 times weekly x 3-4 weeks | IM injection |
| Ovulation-trigger studies (female) | 5000-10,000 IU single dose | Once (timed with follicle maturity) | IM or SubQ |
| PCT protocol | 1000-1500 IU | Every other day x 2-3 weeks | SubQ or IM |
Commonly cycled 12 weeks on, 0+ weeks off.
How it works
At the cell level, HCG research looks at how the hormone binds LH receptors on reproductive tissue — the same receptor luteinizing hormone activates — to trigger downstream hormone production; the terms below just describe those signaling steps.
HCG binds to LH receptors on Leydig cells in the testes, stimulating testosterone and estrogen biosynthesis. In women, it acts on ovarian theca cells to stimulate progesterone production and triggers final oocyte maturation. Half-life is approximately 24-36 hours with peak levels 6-12 hours post-injection. Bioavailability is 40-50% via subcutaneous or intramuscular routes.
Molecular data
These figures — molecular weight, subunit structure, chain length — are the chemistry ID researchers use to confirm an HCG sample's identity; at over 36,000 Da, HCG is one of the largest compounds in this encyclopedia, built from two linked protein subunits rather than a single short chain.
- Weight
- 36700 Da
- Length
- 237 amino acids
- Type
- Heterodimeric glycoprotein with two non-covalently linked subunits
Alpha subunit (92 aa): identical to LH, FSH, and TSH alpha subunits. Beta subunit (145 aa): unique to HCG with 24 aa C-terminal extension not found in LH. Heavy glycosylation (~30% carbohydrate content)
Pharmacokinetics
This chart shows how a research dose of HCG is absorbed and cleared over time in the literature — read it like a timer: the peak is when levels are highest, then the curve trails off as the hormone clears.
- Peak
- 6 hr
- Half-life
- 36 hrs
- Cleared
- ~180 hrs
FDA Pregnyl label
Research applications
This section lists the body systems and approved or off-label research areas scientists have studied for HCG — a summary of what's been studied in the literature, not medical claims about people.
Approved Uses
FDA-approved for prepubertal cryptorchidism not due to anatomical obstruction (dosing: 1000-5000 IU 2-3 times weekly for 3-4 weeks; success rate ~25% as monotherapy). FDA-approved for secondary hypogonadism to stimulate testosterone production, often combined with FSH for spermatogenesis induction (dosing: 1000-2000 IU 2-3 times weekly). FDA-approved as trigger for final follicular maturation and ovulation in assisted reproduction (single dose of 5000-10,000 IU or 250 mcg recombinant when lead follicle reaches 18-20mm).
Off Label Research
Used off-label as TRT adjunct to maintain testicular function, preserve fertility, and prevent testicular atrophy during testosterone replacement therapy.
Body Composition
Off-label research into body composition effects through testosterone stimulation and metabolic modulation.
Dosage reference
- Doses used in research
- Published protocols used 500–1000 IU twice weekly; higher amounts appear in studies where it was used on its own.
- Frequency in studies
- 2-3 times weekly (space doses evenly)
- Handling
- Reconstituted solution — research use only; not for administration
- Timeline reported in studies
- 24-72 hours: testosterone increase begins; 2-4 weeks: noticeable testicular fullness; 6-12 weeks: fertility parameters improve
- Storage
- Lyophilized: room temperature (some products) or refrigerated. Reconstituted: refrigerate 2-8°C, use within 30-60 days
- Cycle length
- Ongoing during TRT; 3-6 months for fertility protocols; 3-4 weeks for cryptorchidism
- Break between cycles
- Not typically cycled when used as TRT adjunct. For PCT, standard 2-3 week protocols
Interactions
This list shows which other hormone-research compounds are studied alongside HCG, and why they commonly appear together in reproductive-endocrine research.
Reconstitution & storage
This is the standard laboratory method for turning freeze-dried HCG powder into a liquid research solution.
- Remove HCG vial and diluent from packaging
- Clean the rubber stoppers of both vials with alcohol swabs
- Draw the diluent (typically 1-2 mL provided) into syringe
- Slowly inject diluent into HCG vial, aiming at the vial wall
- Gently swirl to dissolve - do not shake vigorously
- Allow to sit until completely dissolved and solution is clear
- Calculate concentration: e.g., 5000 IU in 2 mL = 2500 IU/mL
- Label vial with reconstitution date and concentration
Lyophilized: Room temperature (some products) or refrigerated, use within Per manufacturer expiration date
Reconstituted: 2-8°C, use within 30-60 days (depending on diluent and product)
Quality indicators
These are the checks researchers use to confirm an HCG sample is pure, correctly identified, and properly sourced before it's used in a study.
White lyophilized powder - Should appear as white to off-white powder or cake in sealed vial
Clear, colorless reconstituted solution - After reconstitution with provided diluent, solution should be completely clear
Pharmaceutical-grade product with proper labeling - Brands: Pregnyl, Novarel (urinary), Ovidrel (recombinant). Should have clear expiration date and lot number
Proper cold chain for recombinant products - Recombinant HCG (Ovidrel) requires refrigeration throughout shipping and storage
Generic/compounding pharmacy products - Quality varies. Ensure compounding pharmacy is accredited and product is properly stored
Cloudy, discolored, or particles visible - Any turbidity, yellow/brown color, or floating particles indicates degradation
Vial seal compromised or product past expiration - Never use HCG if seal is broken or after expiration date
What to expect
This timeline reflects what the research literature reports at each study stage — research context for comparing studies, not a personal-results promise.
No immediate noticeable effects; HCG is working at cellular level
Testosterone increase detectable on labs; possible improved mood/energy if previously deficient
Testicular fullness/size improvement noticeable; improved sense of well-being
Stable testosterone levels; fertility parameters beginning to improve
Sperm count improvements if used for fertility; sustained testicular function
Maintained testicular size and function with ongoing use; fertility preserved
Safety notes
This section covers regulatory status and handling cautions for HCG — reference context for laboratory researchers, not medical guidance.
- Contraindicated in hormone-sensitive cancers (prostate, breast)
- Risk of ovarian hyperstimulation syndrome (OHSS) in women - requires careful monitoring
- Precocious puberty risk in pediatric patients if used inappropriately
- Thromboembolism risk may be elevated - caution in patients with history of clots
- FDA-approved for specific indications - discuss off-label use with physician
Regulatory status
- Approved by the FDA for at least one indication. That approval applies to regulated pharmaceutical products, not to research-grade material.
- Supplied and described for laboratory research use only — not for human or veterinary use.
Community data
Community Insights
Based on data the community reported. Not clinical proof.
Frequently asked questions
What is HCG studied for in research?
Human Chorionic Gonadotropin (HCG) is a glycoprotein hormone that binds and activates LH receptors. Research and clinical literature describe its role in stimulating Leydig-cell testosterone synthesis and, in reproductive biology, triggering final oocyte maturation. Material supplied here is a research-use-only reference; it is not provided for human use.
How is HCG reconstituted for laboratory use?
HCG usually ships as a lyophilized powder with a separate diluent. The diluent is drawn and injected slowly against the vial wall, then swirled gently — not shaken — until dissolved and clear. Concentration is calculated from the total units per volume (for example 5000 IU in 2 mL gives 2500 IU/mL) and labeled.
How should HCG be stored?
Some lyophilized HCG products are stable at room temperature while others are refrigerated — follow the label. After reconstitution the solution is kept refrigerated at 2-8°C and, depending on diluent and product, used within roughly 30-60 days. Protecting it from heat preserves the glycoprotein for research.
How does HCG differ from kisspeptin?
They act at different points of the reproductive axis: HCG mimics LH directly at the gonad to drive steroid production, while kisspeptin acts upstream in the hypothalamus to stimulate GnRH release. Research studies them as distinct tools for probing different levels of hormonal signaling.
References
Combined HCG and FSH therapy induces spermatogenesis in 70-90% of men with hypogonadotropic hypogonadism. HCG stimulates testosterone production while FSH supports spermatogenesis.
HCG trigger for ovulation induction achieves pregnancy rates of 15-25% per cycle in clomiphene/letrozole protocols and higher in gonadotropin stimulation cycles.
Meta-analysis of HCG for cryptorchidism showing ~25% success rate for hormonal treatment. Surgery remains more effective but HCG/GnRH may have role in bilateral cases or combined therapy.