HCG

Human chorionic gonadotropin (HCG) is a heterodimeric glycoprotein hormone composed of an alpha subunit and a unique beta subunit. The alpha subunit is structurally similar to LH, FSH, and TSH, but the beta subunit dictates HCG's specific binding to the LH/chorionic gonadotropin receptor (LHCGR). HCG activation of this receptor triggers cAMP-dependent pathways crucial for gonadal steroid production in research models. HCG is studied for its ability to promote final follicular maturation and ovulation, enhance early pregnancy progesterone secretion, and stimulate testosterone synthesis in Leydig cells. Its longer biological half-life compared to LH makes HCG an ideal, sustained LH substitute in studies of reproductive endocrinology.

HCG Overview

HCG is synthesized by trophoblast cells and is vital in early pregnancy for supporting the corpus luteum and progesterone synthesis. By activating the LHCGR, HCG initiates intracellular cAMP signaling in gonadal cells. It is used in females to trigger ovulation and luteinization, and in males to stimulate testosterone production and aid spermatogenesis when endogenous LH is compromised. In high concentrations, HCG displays a weak affinity for thyroid receptors. Due to its secretion during pregnancy and by specific tumors, HCG is widely recognized as a highly reliable biochemical marker for both research and diagnostic applications.

HCG Structure

Chemical Makeup

• Molecular Weight: Approximately 36.7 kDa (heterodimer)
• Subunit Masses (COA): alpha-subunit 10,205 Da; beta-subunit 15,547 Da
• Other Known Titles: Human chorionic gonadotropin; Choriogonadotropin; hCG
• CAS: 9002-61-3

HCG Research

HCG Peptide and Fertility Support

HCG serves as an LH analog in assisted reproduction protocols to stimulate the final maturation of follicles and prompt ovulation. A single, timed dose initiates oocyte release and luteinization, which supports corpus luteum activity and progesterone secretion, essential for controlled ovulation and luteal-phase support.

HCG Peptide and Testosterone Stimulation

In male models, HCG activates LHCGR receptors on Leydig cells, driving testosterone synthesis. Research shows that exogenous HCG can restore or sustain intratesticular testosterone levels and promote spermatogenesis in models experiencing suppressed endogenous gonadotropins.

HCG Peptide and Weight Management

Protocols investigating HCG combined with strict calorie restriction for weight loss have been explored. However, controlled studies have consistently determined that HCG does not significantly improve weight loss or alter fat distribution beyond the effects achieved by the diet alone. Observed weight changes are attributed purely to caloric restriction.

HCG Peptide and Endocrine Function

Due to structural similarity with TSH, HCG can display mild thyroid-stimulating properties at elevated concentrations, a mechanism linked to gestational hyperthyroidism. HCG's secretion by some tumors makes it an important ectopic marker. Its prolonged half-life, superior to LH, ensures sustained receptor activation, a feature utilized frequently in experimental endocrine studies.

Article Author

This literature review was compiled, edited, and organized by Dr. Peter Humaidan, M.D., Ph.D. Dr. Humaidan is an internationally recognized reproductive endocrinologist and clinical researcher renowned for his pioneering work on ovulation induction, luteal phase support, and optimization of assisted reproductive technology (ART) protocols. His extensive studies on human chorionic gonadotropin (HCG) and gonadotropin-releasing hormone agonists (GnRHa) have significantly influenced current clinical practice in reproductive medicine and endocrinology.

Scientific Journal Author

Dr. Peter Humaidan has published extensively on the physiological and therapeutic roles of HCG in female fertility, ovulation triggering, and luteal support. His work, alongside collaborators such as B. Alsbjerg, A.D. Coviello, W.J. Bremner, B.J. Schoenfeld, and R. Ramasamy, has advanced the understanding of gonadotropin regulation, testosterone synthesis, and endocrine modulation in both male and female models. This citation is intended solely to acknowledge the scientific and academic work of Dr. Peter Humaidan and his colleagues. It should not be interpreted as an endorsement or promotion of any specific product or organization. Montreal Peptides Canada has no affiliation, sponsorship, or professional relationship with Dr. Humaidan or any of the researchers cited.

Reference Citations

Humaidan P, Alsbjerg B. GnRHa trigger for final oocyte maturation: is HCG trigger history? Reprod Biomed Online. 2014;29(3):274-280 rbmojournal.com. Coviello AD, Matsumoto AM, Bremner WJ, et al. Low-dose human chorionic gonadotropin maintains intratesticular testosterone in normal men with testosterone-induced gonadotropin suppression. J Clin Endocrinol Metab. 2005;90(5):2595-2602 pubmed.ncbi.nlm.nih.gov. Fink J, Schoenfeld BJ, Hackney AC, et al. Human chorionic gonadotropin treatment: a viable option for management of secondary hypogonadism and male infertility. Expert Rev Endocrinol Metab. 2021;16(1):1-8 pubmed.ncbi.nlm.nih.gov. Lee JA, Ramasamy R. Indications for the use of human chorionic gonadotropic hormone for the management of infertility in hypogonadal men. Transl Androl Urol. 2018;7(Suppl 3):S348-S352 imcwc.com. Habous M, Giona S, Tealab A, et al. Clomiphene citrate and human chorionic gonadotropin are both effective in restoring testosterone in hypogonadism: a short-course randomized study. BJU Int. 2018;122(5):889-897 tau.amegroups.org. Liu PY, Wishart SM, Handelsman DJ. A double-blind, placebo-controlled trial of recombinant human chorionic gonadotropin in older men with partial age-related androgen deficiency. J Clin Endocrinol Metab. 2002;87(7):3125-3135 tau.amegroups.org. alTrials.gov. Efficacy and Safety of Long Term Use of hCG or hCG Plus hMG in Males With Isolated Hypogonadotropic Jonadism (IHH). (Tongji Hospital study NCT03687606) centerwatch.com.

STORAGE

Storage Instructions

All products are manufactured via lyophilization (freeze-drying), ensuring stability during shipping (approximately 3–4 months). Lyophilization is a specialized dehydration method that results in a stable, white crystalline powder, which can be stored safely at room temperature until reconstitution with bacteriostatic water.

Best Practices for Storing Lyophilized Peptides

• General: Store peptides in a cold, dry, and dark environment and protect them from light.
• Short-Term Storage (Days to Months): Refrigeration below 4°C (39°F) is sufficient. Lyophilized peptides remain stable at room temperature for several weeks.
• Long-Term Storage (Months to Years): For optimal stability, store peptides in a freezer at -80°C (-112°F).
• Handling: Minimize air and moisture exposure. Always allow the cold vial to reach room temperature before opening to prevent condensation.
• Aliquot: To minimize degradation from repeated freeze-thaw cycles and air exposure, divide the total peptide quantity into smaller aliquots for individual experimental use.
• Freezer Type: Avoid frost-free freezers due to temperature variations during defrosting.

Storing Peptides In Solution (Reconstituted)

• Peptide solutions are susceptible to bacterial degradation and have a shorter shelf life.
• Reconstituted Stability: Once mixed with bacteriostatic water, solutions should be stored in a refrigerator and remain stable for up to 30 days.
• Buffer/pH: If storage in solution is necessary, use sterile buffers with a pH between 5 and 6.
• Handling: Divide the solution into aliquots to minimize freeze-thaw cycles.
• Sensitive Peptides: Peptides containing Cysteine (C), Methionine (M), Tryptophan (W), Aspartic acid (Asp), Glutamine (Gln), or N-terminal Glutamic acid (Glu) degrade more rapidly in solution and should be frozen when not in immediate use.