HCG (Human Chorionic Gonadotropin)

What Is HCG?

Human Chorionic Gonadotropin (HCG) is a naturally occurring glycoprotein hormone produced by the placenta during pregnancy. It consists of an alpha subunit shared with LH, FSH, and TSH, and a unique beta subunit that gives it its specific biological activity. HCG mimics luteinizing hormone (LH) by binding to the same receptors in the gonads.

In research and clinical settings, HCG is widely used for its ability to stimulate gonadal function. In males, it directly stimulates Leydig cells to produce testosterone, making it valuable for hormonal support during and after exogenous hormone protocols. In females, it is used to trigger ovulation in fertility treatments.

Mechanism of Action

LH Receptor Agonism

HCG binds to luteinizing hormone/choriogonadotropin receptors (LHCGR) on Leydig cells in the testes and theca cells in the ovaries. This binding activates cAMP-mediated signaling cascades that stimulate steroidogenesis – the production of testosterone in males and progesterone in females.

Testicular Stimulation

By mimicking LH, HCG maintains intratesticular testosterone (ITT) production even when the hypothalamic-pituitary-gonadal (HPG) axis is suppressed by exogenous hormones. This preserves testicular volume, spermatogenesis, and Leydig cell sensitivity during TRT or anabolic protocols.

Ovulation Induction

In female subjects, HCG triggers the final maturation and release of oocytes from mature follicles, mimicking the natural LH surge that precedes ovulation. This mechanism is the basis for its use in assisted reproductive technology (ART) protocols.

Downstream Hormonal Effects

HCG-stimulated testosterone production leads to downstream aromatization to estradiol, which is important for bone density, lipid metabolism, and cognitive function. It also supports pregnenolone and DHEA production through stimulation of the steroidogenic pathway.

Research Applications

• Post-cycle therapy (PCT) – Restoring endogenous testosterone production after HPG axis suppression
• On-cycle support – Maintaining testicular function and ITT during exogenous hormone use
• Male fertility – Preserving or restoring spermatogenesis in hypogonadal models
• Female fertility – Ovulation induction in ART and IVF protocols
• Testosterone replacement adjunct – Preventing testicular atrophy during long-term TRT
• Hormonal cascade research – Studying LH-receptor-mediated steroidogenesis and downstream metabolite production

Dosing Protocols

All protocols are for research reference only. Consult a qualified medical professional before use.

Preparation & Storage

Reconstitution

Supplies: peptide vial, bacteriostatic water, insulin syringes (29–31 gauge), alcohol swabs.

1. Clean both vial tops with alcohol swabs and let dry
2. Draw 2 mL of bacteriostatic water into the syringe
3. Insert needle into peptide vial at an angle against the glass wall
4. Let water run slowly down the side – never squirt directly onto powder
5. Gently swirl until fully dissolved – never shake
6. Solution should be clear – discard if cloudy or contains particles

Concentration: 5,000 IU in 2 mL = 2,500 IU/mL

Storage

• Unreconstituted: Room temp or refrigerated, stable up to 24 months
• Reconstituted: Refrigerate at 2–8°C (36–46°F), use within 4–6 weeks
• Protect from direct sunlight and heat
• Do not freeze reconstituted solution

Cycling

Typical research cycle: As directed. Results generally reported within 1–2 weeks.