HCG (Human Chorionic Gonadotropin) (Research Overview)
Human chorionic gonadotropin (hCG) is a glycoprotein hormone made of two non-identical subunits, an alpha subunit and a beta subunit. Unlike the short synthetic peptides in the catalogue, it is a large, heavily glycosylated protein, which is why its listed molecular weight of about 36,700 Da is approximate: the mass of a glycoprotein depends on the sugars attached to it.
Mechanism of Action
hCG belongs to a family of glycoprotein hormones that includes luteinizing hormone (LH), follicle-stimulating hormone (FSH) and thyrotropin (TSH). These hormones share a common alpha subunit and differ in their beta subunits, and the beta subunit confers receptor and biological specificity. LH and hCG bind the same G protein-coupled receptor, the luteinizing hormone-choriogonadotropin receptor (LHCGR), through its large extracellular domain.
Cryo-electron microscopy structures of the full-length receptor have been reported in inactive and active states, with the active structures bound to chorionic gonadotropin and the stimulatory G protein (Gs). The structures describe a push-and-pull mechanism of receptor activation. Earlier crystallography showed that each hCG subunit folds as a cystine knot, with three disulphide bonds, and that a segment of the beta subunit wraps around the alpha subunit like a seat belt, held by the disulphide Cys 26-Cys 110, a feature that appears essential for subunit association and receptor binding.
Research Areas
Structure and glycosylation: the alpha subunit has two N-glycosylation sites, and the beta subunit has two N-glycosylation sites and four O-glycosylation sites. The carboxy-terminal extension of the beta subunit carries four serine O-linked oligosaccharides and has been identified as important for the long half-life of hCG in engineering studies of the glycoprotein hormones.
Heterogeneity: the glycosylation pattern of hCG varies with its source of production, so preparations are mixtures of glycoforms rather than a single species. This is a central reason that glycoproteins are characterized with different tools than short peptides.
Analytical background: a review of hCG immunoassays lists many hCG-related molecules, including nicked hCG, hyperglycosylated and hypoglycosylated forms, free subunits and the beta-core fragment, and notes that different assays measure different combinations of them, which is the source of discordance between methods. The same review examines the stability and degradation of hCG.
Findings from published studies describe molecular structure and receptor biochemistry and do not establish safety or efficacy for any indication; they should not be interpreted as medical claims.
What the published literature reports
This section summarizes what published studies report. It describes study designs and results as the authors reported them. It does not describe any use of the research materials sold on this site, and it is not a recommendation, instruction or claim about any product.
Study models and endpoints
- Model Structural biology (X-ray crystallography, cryo-electron microscopy) and glycoprotein-hormone biochemistry. [1][2][5]
- Model Reviews of hCG glycoforms and immunoassays. [3][4]
- Model A criteria-based meta-analysis of published trials of hCG in obesity. [6]
- Endpoint Three-dimensional structure and receptor activation. [1][5]
- Endpoint Weight loss, fat redistribution, hunger and well-being as reported by the trials in the meta-analysis. [6]
Reported findings
- A 1994 crystal-structure study reported that each of the two hCG subunits has a similar topology with three disulphide bonds forming a cystine knot, and that a segment of the beta-subunit wraps around the alpha-subunit like a seat belt. [1]
- A 2021 cryo-EM study reported structures of the luteinizing hormone/choriogonadotropin receptor in inactive and active states and described a push-and-pull activation mechanism in which a hinge-loop fragment acts as a tethered agonist. [5]
- A review reported that the hCG glycosylation state varies with stage of pregnancy, source of production and pathology, and that hCG concentrations in maternal blood peak at 8 to 10 weeks of gestation. [3]
- A review reported that multiple hCG-related molecules are present in pregnancy serum and urine and that over 100 immunoassays each measure non-nicked hCG plus a different combination of the other molecules, which is the source of interassay discordance. [4]
- A criteria-based meta-analysis of 8 controlled and 16 uncontrolled trials of hCG in obesity reported that most studies were of poor methodological quality and concluded that there is no scientific evidence that hCG is effective in the treatment of obesity. [6]
Evidence level and limitations
Evidence level: Published human trials exist for this compound. Where cited, they tested pharmaceutical products under clinical protocols and say nothing about laboratory research material.
- Most cited papers are structural, biochemical or review papers and are not clinical outcome studies. [1][2][3][4][5]
- The meta-analysis was criteria-based and included uncontrolled trials; it scored most studies as of poor methodological quality. [6]
Regulatory status
- As of 16 October 2026, FDA states that there are no FDA-approved hCG products for weight loss, and that FDA-approved uses of prescription hCG products are for female fertility and select hormonal treatment in males. FDA-approved hCG labeling states that hCG has not been demonstrated to be effective adjunctive therapy in the treatment of obesity. Those approved prescription products are different from any laboratory research material.
Sources checked on 16 October 2026: FDA, "Questions and Answers on HCG Products for Weight Loss"; FDA-approved labeling, Novarel (chorionic gonadotropin), DailyMed. Regulatory status can change.
Not established
- Effectiveness of hCG for weight loss, fat redistribution or hunger is not established; the cited meta-analysis found no scientific evidence for it. [6]
Summaries of published literature, not claims about any product sold here. For laboratory research use only.
Specification summary
HCG
Stated purity ≥99%. For laboratory research use only.
Related materials
Laboratory background
Education for people working with this material in the laboratory: guides on handling and analysis, definitions of terms, and arithmetic tools. It describes no use of the material.
Guides
Glossary terms
References
- Lapthorn AJ, Harris DC, Littlejohn A, Lustbader JW, Canfield RE, Machin KJ, et al. Crystal structure of human chorionic gonadotropin. Nature. 1994;369(6480):455-61. PMID 8202136 · DOI
- Boime I, Ben-Menahem D. Glycoprotein hormone structure-function and analog design. Recent Prog Horm Res. 1999;54:271-88; discussion 288-9. PMID 10548880
- Fournier T. Human chorionic gonadotropin: Different glycoforms and biological activity depending on its source of production. Ann Endocrinol (Paris). 2016;77(2):75-81. PMID 27177499 · DOI
- Cole LA. Immunoassay of human chorionic gonadotropin, its free subunits, and metabolites. Clin Chem. 1997;43(12):2233-43. PMID 9439438
- Duan J, Xu P, Cheng X, Mao C, Croll T, He X, et al. Structures of full-length glycoprotein hormone receptor signalling complexes. Nature. 2021;598(7882):688-692. PMID 34552239 · DOI
- Lijesen GK, Theeuwen I, Assendelft WJ, Van Der Wal G. The effect of human chorionic gonadotropin (HCG) in the treatment of obesity by means of the Simeons therapy: a criteria-based meta-analysis. Br J Clin Pharmacol. 1995;40(3):237-43. PMID 8527285 · DOI
Cited literature is provided for scientific context only and does not describe or endorse any use of these products.
For laboratory research use only. Not for human or veterinary use. Not intended to diagnose, treat, cure, or prevent any disease.