HCG

HCG Overview

Human Chorionic Gonadotropin (HCG) is a complex heterodimeric glycoprotein hormone that plays a fundamental role in mammalian reproductive biology. It is composed of two non-covalently linked subunits: the alpha subunit and the beta subunit. While the alpha subunit is structurally identical to those found in luteinizing hormone (LH), follicle-stimulating hormone (FSH), and thyroid-stimulating hormone (TSH), the beta subunit is unique to HCG. This specific beta chain is responsible for its distinct biological activity and its high affinity for the LH/chorionic gonadotropin receptor (LHCGR).

In research and clinical models, HCG acts as a powerful analog for LH. Because it possesses a significantly longer biological half-life than natural LH, it allows for sustained stimulation of target tissues. Its primary functions include the support of the corpus luteum in females to maintain progesterone production and the stimulation of Leydig cells in males to produce testosterone. Beyond its reproductive roles, HCG is studied as a biochemical marker due to its secretion by trophoblast cells and certain types of tumors, making it a focal point in both gestational research and oncology.

HCG Structure

The structural integrity of HCG is defined by its specific glycosylation patterns and the precise folding of its two protein subunits. The following table summarizes the key chemical and physical properties of the HCG molecule:

Property

Description

Chemical Name

Human Chorionic Gonadotropin

Molecular Weight

Approximately 36.7 kDa (Total Heterodimer)

Alpha Subunit Mass

10,205 Da

Beta Subunit Mass

15,547 Da

CAS Number

9002-61-3

Common Aliases

Choriogonadotropin, hCG, Pregnancy Hormone

Primary Sequence Length

237 Amino Acids (Combined Subunits)

Structure Solution Formula:

The chemical composition of the HCG glycoprotein can be represented by the empirical formula C1105H1770N318O336S26. This formula accounts for the amino acid backbone of both the alpha and beta subunits before the addition of complex carbohydrate side chains (glycosylation), which significantly contribute to its final functional molecular weight.

HCG Research

HCG and Fertility Support

In reproductive endocrinology studies, HCG is primarily utilized to mimic the endogenous LH surge. In female models, the administration of HCG triggers the final stages of follicular maturation and induces oocyte release (ovulation). Furthermore, it supports the transformation of the follicle into the corpus luteum, ensuring the secretion of progesterone necessary for uterine receptivity. Its reliability in these processes makes it a standard tool in research involving assisted reproductive technologies (ART) and ovulation induction protocols.

HCG and Testosterone Stimulation

In male physiological research, HCG serves as a potent stimulator of the interstitial cells of the testes. By binding to LHCGR on Leydig cells, it bypasses the pituitary gland to directly signal the production of intratesticular testosterone. Research indicates that HCG can maintain or restore sperm production (spermatogenesis) and testosterone levels even when the natural production of gonadotropins is suppressed by external factors or medical conditions.

HCG and Weight Management

There has been historical interest in HCG as a potential aid for weight loss, often paired with very low-calorie diets. However, contemporary scientific literature and controlled research trials have clarified this relationship. Data consistently shows that HCG does not directly facilitate fat loss or suppress appetite. Any weight reduction observed in subjects is attributed to the caloric deficit of the diet itself rather than the pharmacological properties of the peptide.

HCG and Endocrine Function

Due to the structural similarities between the alpha subunit of HCG and TSH, extremely high concentrations of HCG can cross-react with thyroid receptors. Research into gestational hyperthyroidism often focuses on this "weak" thyroid-stimulating effect. Additionally, HCG is explored as a tumor marker, as ectopic secretion of the hormone is associated with various germ cell and non-germ cell malignancies, providing insights into tumor progression and diagnostic monitoring.

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, contributing to the refinement of controlled ovarian stimulation protocols. Alongside collaborators such as B. Alsbjerg, A.D. Coviello, W.J. Bremner, B.J. Schoenfeld, and R. Ramasamy, his work has advanced understanding of gonadotropin regulation, testosterone synthesis, and endocrine modulation in both male and female models. Dr. Humaidan’s contributions continue to inform research in reproductive endocrinology, hormone regulation, and clinical infertility management.

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.

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.

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.

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.

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.

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.

ClinicalTrials.gov. Efficacy and Safety of Long Term Use of hCG or hCG Plus hMG in Males With Isolated Hypogonadotropic Hypogonadism (IHH). (Tongji Hospital study NCT03687606).

STORAGE

Storage Instructions

All products are produced through a lyophilization (freeze-drying) process, which preserves stability during shipping for approximately 3 to 4 months. After reconstitution with bacteriostatic water, peptides must be stored in a refrigerator to maintain their effectiveness. Once mixed, they remain stable for up to 30 days.

Lyophilization, also known as cryodesiccation, is a specialized dehydration method in which peptides are frozen and exposed to low pressure. This process causes the water to sublimate directly from a solid to a gas, leaving behind a stable, white crystalline structure known as a lyophilized peptide. The resulting powder can be safely kept at room temperature until it is reconstituted.

For extended storage periods lasting several months to years, it is recommended to keep peptides in a freezer at -80 degrees Celsius. Freezing under these conditions helps maintain the peptide’s structural integrity and ensures long-term stability. Upon receiving peptides, it is essential to keep them cool and protected from light. For short-term use, refrigeration below 4 degrees Celsius is sufficient.

Best Practices For Storing Peptides

Proper storage of peptides is critical to maintaining the accuracy and reliability of laboratory results. Following correct storage procedures helps prevent contamination, oxidation, and degradation.

• Temperature Management: Upon receipt, keep peptides cool and shielded from light. Refrigeration below 4 degrees Celsius is suitable for use within a few months. For long-term preservation, use a freezer at -80 degrees Celsius.
• Avoid Fluctuations: Minimize freeze-thaw cycles, as repeated temperature changes accelerate degradation. Avoid frost-free freezers because their self-defrosting cycles cause temperature spikes.
• Moisture Protection: Always allow the vial to reach room temperature before opening to prevent condensation from forming on the cold powder.
• Oxidation Prevention: Keep containers closed and promptly reseal them after use. Storing remaining material under an inert gas like nitrogen can further protect sensitive residues like cysteine and methionine.
• Aliquot Method: Divide the total peptide quantity into smaller aliquots for individual experimental use. This prevents the entire stock from being exposed to air and temperature changes multiple times.

Storing Peptides In Solution

Peptide solutions have a much shorter shelf life than lyophilized powders. They are highly susceptible to bacterial growth and chemical degradation. If storage in solution is necessary, use sterile buffers with a pH between 5 and 6. Divide the solution into aliquots and keep them refrigerated at 4 degrees Celsius for up to 30 days. For any period longer than this, the solution should be frozen, though this may still result in some loss of activity.

Peptide Storage Containers

Containers must be clean, clear, durable, and chemically resistant. Glass vials are generally preferred for their chemical inertness and clarity. If using plastic, polypropylene is favored over polystyrene for its superior chemical resistance. The vial should be appropriately sized to minimize the volume of air (headspace) inside the container.

Peptide Storage Guidelines: General Tips

• Store in a cold, dry, and dark environment.
• Avoid repeated freeze-thaw cycles.
• Minimize exposure to air to prevent oxidation.
• Protect from light to avoid structural changes.
• Keep lyophilized as long as possible; do not store in solution long term.
• Use aliquots to prevent unnecessary handling of the bulk stock.