Overview
In plain English
HCG is a hormone, not a peptide. It is best known from pregnancy testing, but in this context it is used because it acts on the same receptor as luteinising hormone — the signal that tells the testes to make testosterone.
The main use is alongside TRT: exogenous testosterone shuts down that signal, and HCG replaces it so the testes keep working. It is also used in fertility and post-cycle protocols.
- What it isA glycoprotein hormone that mimics luteinising hormone
- Mainly used forMaintaining testicular function and fertility on TRT
- Typical protocol250iu daily, reassessed with bloodwork every 8–12 weeks
How it works
What it actually does
Testosterone production runs on a signal from the brain. When you take testosterone from outside, the brain sees enough and stops sending that signal — so the testes go quiet and shrink.
HCG binds the same receptor as that signal. The testes carry on producing, and testicular volume and fertility are maintained.
It lasts far longer in the blood than the natural signal does, because of extra sugar chains and a longer tail on the molecule — which is why a small daily dose is enough.
The science in detail
HCG is not a peptide in the sense that most of this catalogue is. It is a heterodimeric glycoprotein hormone, produced by the syncytiotrophoblast during pregnancy, and it belongs to the same structural family as luteinising hormone, follicle-stimulating hormone and thyroid-stimulating hormone. All four share a common alpha subunit; specificity resides entirely in the beta subunit, which associates non-covalently with the alpha chain to form the active hormone. Neither subunit is active alone.
The target is the luteinising hormone / choriogonadotropin receptor, a class A G-protein-coupled receptor expressed on Leydig cells in the testis and on theca and granulosa cells in the ovary. Receptor occupancy activates adenylate cyclase, raises cAMP and drives protein kinase A signalling, with steroidogenic acute regulatory protein mobilising cholesterol to the inner mitochondrial membrane as the rate-limiting step in steroid synthesis.
HCG and LH act at the same receptor, which is why HCG functions experimentally as an LH surrogate. The pharmacologically significant difference is duration. The HCG beta subunit carries a C-terminal peptide extension bearing additional O-linked glycosylation, and this heavily sialylated tail markedly slows renal clearance. The result is a far longer circulating half-life than native LH, which is what makes the molecule useful as a sustained stimulus in gonadal research models.
The human literature is substantial and long-established. Matsumoto, Karpas and Bremner (Journal of Clinical Endocrinology & Metabolism, 1986) administered HCG chronically to normal men, suppressing FSH to undetectable levels, and demonstrated that FSH replacement was required to restore quantitatively normal sperm production — establishing the division of labour between the two gonadotropins. Coviello et al. (Journal of Clinical Endocrinology & Metabolism, 2005) reported that low-dose HCG maintained intratesticular testosterone in normal men with testosterone-induced gonadotropin suppression, a study frequently cited in subsequent work on gonadal axis suppression.
Because it is a glycoprotein rather than a synthetic peptide, batch characterisation and handling differ meaningfully from the rest of this catalogue.
Evidence
What the research shows
Acts on the same receptor as LH
It substitutes for the brain's signal to the testes, which exogenous testosterone suppresses.
Much longer-lasting than natural LH
Structural differences give it a far longer half-life, so low daily doses are effective.
Low doses maintain testicular testosterone
A published clinical study found intratesticular testosterone maintained at low HCG doses.
Shares structure with LH, FSH and TSH
It belongs to the same hormone family; only one half of the molecule gives it its specificity.
Mixing & dosage
How to mix and dose it
These are the mixing and dosage instructions supplied by Purist Peptides and the manufacturer for this product.
A 3ml vial of bacteriostatic water is included free with every peptide vial you order, so you have what you need to mix this on arrival.
HCG 5,000iu
Step 1 — mix your vial
- Draw up 1ml of bacteriostatic water into a syringe
- Wipe the rubber top of your vial with an alcohol swab and let it dry
- Insert the needle then slowly and carefully push the water down the inside wall of the vial — do not inject water straight onto the peptide powder
- Gently roll the vial between your palms until the powder dissolves completely
- Do not shake
- Allow to settle in the fridge for 5–10 minutes. The liquid should look clear
Step 2 — draw & inject your dose
Use a 1ml insulin syringe to draw and inject your dose. A 1ml syringe = 100 units.
With 1ml of water added, each 0.1ml (10 units) you draw = 500iu of HCG.
| Stage | Dose | On the syringe |
|---|---|---|
| Standard | 250iu daily | 5 units |
Vial duration at standard dose: 20 days
When to inject: Daily at a consistent time. Most commonly used alongside TRT to maintain testicular function.
Cycle length: Ongoing as directed. Reassess with bloodwork every 8 to 12 weeks.
HCG 10,000iu
Step 1 — mix your vial
- Draw up 2ml of bacteriostatic water into a syringe
- Wipe the rubber top of your vial with an alcohol swab and let it dry
- Insert the needle then slowly and carefully push the water down the inside wall of the vial — do not inject water straight onto the peptide powder
- Gently roll the vial between your palms until the powder dissolves completely
- Do not shake
- Allow to settle in the fridge for 5–10 minutes. The liquid should look clear
Step 2 — draw & inject your dose
Use a 1ml insulin syringe to draw and inject your dose. A 1ml syringe = 100 units.
With 2ml of water added, each 0.1ml (10 units) you draw = 500iu of HCG.
| Stage | Dose | On the syringe |
|---|---|---|
| Standard | 250iu daily | 5 units |
Vial duration at standard dose: 40 days
When to inject: Daily at a consistent time. Most commonly used alongside TRT to maintain testicular function.
Cycle length: Ongoing as directed. Reassess with bloodwork every 8 to 12 weeks.
How to inject
- Wipe your injection site with an alcohol swab and let it dry
- Pinch a small fold of skin on your abdomen
- Insert the needle at a 45-degree angle into the pinched skin
- Slowly push the plunger down until empty
- Pull the needle out and apply gentle pressure with the swab
- Dispose of the needle safely in a sharps container — never recap or reuse
Storage
Keep refrigerated at 2 to 6 degrees Celsius at all times after mixing. Do not freeze. Protect from light and label the vial with the date you reconstituted it. Discard any solution that is hazy, discoloured or contains particles.
For informational purposes only. This is not medical advice. Speak to a qualified healthcare professional before starting any compound.
Questions
Frequently asked questions
Why is HCG measured in international units rather than milligrams?
Because it is a glycoprotein whose activity depends on glycosylation as well as sequence, potency is defined against a biological reference standard rather than by mass. Two preparations of identical mass may differ in activity, so international units are the meaningful specification.
How does HCG differ from luteinising hormone?
Both act at the same receptor. The difference is duration: the HCG beta subunit carries a C-terminal peptide extension with additional sialylated O-linked glycans, which slows renal clearance substantially and gives a far longer circulating half-life than native LH.
What has HCG been studied for in the research literature?
Gonadal steroidogenesis, intratesticular testosterone, and the respective roles of LH and FSH in spermatogenesis. Matsumoto et al. (JCEM, 1986) and Coviello et al. (JCEM, 2005) are two frequently cited examples. Purist supplies the compound for laboratory research only.
Why does it require different handling from the synthetic peptides?
It is a much larger molecule held together by a non-covalent association between two subunits. That association can be lost to shear or interfacial stress without any visible change in the solution, and activity is lost with it. Reconstituted stability windows are also shorter.
How is purity verified?
Every batch is assayed by independent HPLC at Bioindustrial Services in Boksburg. We do not rely on the manufacturer's own certificate alone. The assay report for the batch you receive is available on request, and our full testing protocol is set out at Quality Standards.
How long does delivery take?
Orders are dispatched from South Africa, with timelines varying by region and courier. Current dispatch and transit windows are set out at Delivery Process.
What is the returns policy?
Unopened vials in original condition may be returned under the conditions set out at Refund Policy.
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