HCG (5000iu)

What is HCG (Human Chorionic Gonadotropin)?

Human chorionic gonadotropin (HCG) is a naturally occurring placental glycoprotein hormone that interacts with the luteinizing hormone/choriogonadotropin receptor (LHCGR). It is structured as a disulfide-rich heterodimer composed of a common 92-amino-acid alpha subunit and a unique 145-amino-acid beta subunit. In preclinical research, HCG is used to explore luteinizing hormone receptor signaling, reproductive endocrinology, paracrine crosstalk, and angiogenic pathways.

Chemical Structure of HCG

HCG is a heterodimeric glycoprotein (~37.9 kDa molecular mass, ~30% carbohydrate by weight) composed of:

• Alpha subunit: 92 amino acids, shared among LH, FSH, TSH, and HCG.
• Beta subunit: 145 amino acids, including a unique 24-residue C-terminal peptide (CTP) that extends its half-life.
• Glycosylation: Eight carbohydrate chains (two N-linked on α, two N-linked plus four O-linked on β) improve stability and bioavailability.
• Cystine-knot motif: Both subunits feature three disulfide bonds forming a rigid tertiary structure crucial for receptor binding.

What Are the Effects of HCG?

• LHCGR-Mediated Signaling: HCG activates Gs and Gq pathways upon binding LHCGR, resulting in cAMP production and steroidogenesis in gonadotrophin-responsive cells.
• Angiogenic and Paracrine Effects: In vitro studies show HCG stimulates endothelial cells to produce angiogenic factors such as VEGF.
• Reproductive Endocrine Modulation: Research shows HCG enhances progesterone secretion and supports oocyte maturation in granulosa cells.
• Biased Agonism: HCG triggers distinct intracellular signaling kinetics compared to LH, exhibiting unique LHCGR-mediated effects on cAMP and gene expression.

Citations

1. RCSB PDB – “Structure of human chorionic gonadotropin at 2.6 Å resolution” Overview of HCG Structure and Receptor Interaction
2. Sigma-Aldrich – “Human chorionic gonadotropin (HCG): glycoprotein heterodimer overview” Overview of HCG Structure and Receptor Interaction
3. Frontiers in Immunology – “HCG induces angiogenic responses via LHCGR activation” Overview of HCG Structure and Receptor Interaction
4. MDPI Int. J. Mol. Sci. – “HCG promotes oocyte maturation and embryo development” Overview of HCG Structure and Receptor Interaction
5. Reproductive Biology and Endocrinology – “Biological functions of HCG variants” Overview of HCG Structure and Receptor Interaction
6. Cell/Structure – “Three-dimensional structure of HCG reveals cystine-knot fold” Overview of HCG Structure and Receptor Interaction