🛡️HCG (Human Chorionic Gonadotropin)
LH-receptor agonist glycoprotein hormone. The gold-standard research tool for Leydig cell steroidogenesis, ovarian function, HPG axis regulation and IVF research.
Glycoprotein — α (92 aa) + β (145 aa) subunitsWhat Is HCG?
Human Chorionic Gonadotropin (HCG) is a 237-amino-acid glycoprotein composed of an alpha subunit (92 aa, shared with LH/FSH/TSH) and a beta subunit (145 aa, unique). It binds the LH receptor (LHR) with equal affinity to endogenous LH. HCG has been used clinically since the 1950s.
Key Mechanisms
- LHR agonism — activates testicular Leydig cell cAMP/PKA/StAR steroidogenic cascade
- Testosterone synthesis — primary pharmacological tool for studying male HPG axis
- Ovulation induction — triggers follicular rupture in ART protocols
- Corpus luteum maintenance — maintains progesterone production in early pregnancy models
Key References
- Bosch E et al. "ESHRE guideline: ovarian stimulation for IVF/ICSI." Hum Reprod Open, 2020;2020(2):hoaa009.
- Raivio T et al. "Reversal of idiopathic hypogonadotropic hypogonadism." N Engl J Med, 2007;357:863–873.
Frequently Asked Questions
No, but it acts on the same receptor. HCG and luteinising hormone (LH) both bind the LH receptor (LHR) with similar affinity, which is why HCG is used as a long-acting LH-receptor research surrogate — its half-life (24–36h) is far longer than endogenous LH's.
HCG selectively activates the LH-receptor pathway, while HMG (human menopausal gonadotropin) contains a mix of FSH and LH activity — the two are used to model different arms of the HPG axis.
As a lyophilized powder, commonly labelled in IU (e.g. 5000 IU), that requires reconstitution with bacteriostatic water before use — see the reconstitution calculator for the concentration math.