HCG 10000iu

Human chorionic gonadotropin (hCG) is a glycoprotein hormone made by the placenta, built from an alpha and a beta subunit with 237 amino acids between them and about 30% of its mass as carbohydrate. This listing is the 10,000 IU vial of urinary hCG, supplied as a white freeze-dried cake; a 5,000 IU fill is also sold. Published work on hCG covers its subunit structure and glycosylation, the several forms it takes in pregnancy and in trophoblastic tumors, and the reference standards used to measure it.

Specifications

Fills in this range

HCG is sold in 2 fills. The compound and the testing are the same in every fill; only the amount in the vial changes.

What 10,000 IU measures

An international unit is a measure of biological activity relative to a reference preparation, not a quantity of substance. The certificate puts this fill at roughly 1 mg of glycoprotein, standardized by bioassay, and the HCG 5,000 IU vial at roughly half that. Even the mass of one molecule is a spread rather than a single number: LC-MS gives a centroid of 36,712 Da across glycoforms of 36 to 38 kDa, built on a protein core of 25.7 kDa.

The loose link between units and weight comes from how units are assigned. When the WHO set up its International Standard for FSH, a closely related glycoprotein hormone, 27 laboratories in 13 countries assayed it by several methods¹. The in vivo bioassays agreed within and between laboratories at about 80 IU per ampoule, in vitro bioassays and receptor assays agreed at about 31, and 19 immunoassay systems returned anything from 5 to 31¹. The unitage was set from the in vivo bioassay, the method judged to identify and define the hormone best¹.

Handling notes

Most short synthetic peptides in the catalogue are kept at −20 °C. hCG is a protein, and the certificate gives 2 to 8 °C, in the dark, for the sealed vial. Let the vial reach room temperature before opening so that moisture does not condense on the cake. A solution is kept at 2 to 8 °C, protected from light, for a period your laboratory has established.

The safety data sheet classifies hCG as a reproductive toxicant in category 1A (H360Fd) and as causing organ damage through prolonged or repeated exposure (H372). It is stored locked up and handled with the precautions the sheet sets out. General guidance on keeping proteins and peptides is in peptide storage and stability.

What the research covers

Two subunits and their sugars

hCG is one of the glycoprotein hormones. Its alpha subunit is identical to the alpha subunit of the pituitary hormones LH, FSH and TSH, carries two N-glycosylation sites and is encoded by a single gene, CGA². Beta subunits differ from one hormone to the next and give each its receptor and biological specificity; the hCG beta subunit has two N-glycosylation and four O-glycosylation sites and is encoded by a cluster of genes, CGB². The two subunits are joined non-covalently³. The certificate puts numbers on the same molecule: a 92-residue alpha chain, a 145-residue beta chain that ends in a 24-residue C-terminal peptide, and 11 disulfide bonds.

One name for several forms

In structure hCG resembles LH, but Cole’s 2009 review described it as a set of hormonal and non-endocrine agents where LH is a single molecule: regular hCG, hyperglycosylated hCG and the free beta-subunit of the hyperglycosylated form³. Regular hCG had been known for 88 years as a promoter of progesterone production by the corpus luteum, a function that accounts for only about three weeks of its output across a pregnancy³. Cole summarized later work giving it roles in trophoblast differentiation and in fetal nutrition, through angiogenesis of the spiral arteries in the myometrium³. The two main forms come from different cells. Fused villous syncytiotrophoblast makes regular hCG, while invasive extravillous cytotrophoblast makes the hyperglycosylated variant, which acts back on those same cells to start and control invasion at implantation and, in invasive hydatidiform mole and choriocarcinoma, malignant growth³. In those cells it also inhibits apoptosis³.

Fournier and colleagues approached the hormone from the placental side. They called hCG the first hormonal message from the placenta to the mother, detectable in maternal blood two days after implantation, acting like an LH agonist on the corpus luteum and also involved in quiescence of the myometrium and local immune tolerance². Levels in maternal blood peak at around 8 to 10 weeks of gestation, and the glycosylation of the hormone shifts with the stage of pregnancy, the cell producing it and disease².

Reference materials for measurement

With so many related forms in circulation, measuring hCG consistently has needed purpose-made standards. Birken and colleagues reported in 2003 that the standards then used for hCG and its alpha and beta subunits contained substantial amounts of contaminating variants and other impurities⁴. For an IFCC working group they prepared new reagents for intact hCG, the free subunits, nicked hCG and nicked beta subunit (with cuts in the beta backbone between residues 44 and 45 or 47 and 48), and the beta-core fragment, in which residues 6 to 40 and 55 to 92 of the beta chain are held together by disulfide bridges⁴. Each preparation was characterized by amino acid and sequence analysis, carbohydrate composition and electrophoresis, and its concentration was set by amino acid analysis⁴.

What these papers do not show

The literature cited here is about hCG as the body makes it and about how laboratories standardize its measurement. None of the abstracts compares a urinary preparation with the forms that circulate in pregnancy, and none of the work used PrymaLab material. The certificate gives purity and a centroid mass for the intact hormone; it does not resolve regular, hyperglycosylated, nicked or free-subunit forms, so their share in a given lot is not reported. The hCG guide covers more of the literature.

How each lot is tested

Every lot is tested in PrymaLab’s own laboratory in Ashland, Kentucky before release: RP-HPLC for purity, LC-MS for identity, Karl Fischer titration for water, LAL for endotoxin and USP <71> for sterility. The results for the lot now shipping are in the certificate panel on this page, and the certificate number, key and QR code can be checked on the verify page. These are in-house results from PrymaLab Analytical, not an independent test, and the lab is not accredited to ISO 17025. The third-party testing guarantee on this page still applies: if any independent laboratory finds the wrong compound, or less than the stated purity or amount, the order is refunded and the cost of the test is reimbursed.

Frequently asked questions

References

1. Storring PL, Gaines Das RE. The International Standard for Pituitary FSH: collaborative study of the Standard and of four other purified human FSH preparations of differing molecular composition by bioassays, receptor assays and different immunoassay systems. J Endocrinol. 1989;123(2):275-93. DOI · PubMed
2. Fournier T, Guibourdenche J, Evain-Brion D. Review: hCGs: different sources of production, different glycoforms and functions. Placenta. 2015;36 Suppl 1:S60-5. DOI · PubMed
3. Cole LA. New discoveries on the biology and detection of human chorionic gonadotropin. Reprod Biol Endocrinol. 2009;7:8. DOI · PubMed
4. Birken S, Berger P, Bidart JM, et al. Preparation and characterization of new WHO reference reagents for human chorionic gonadotropin and metabolites. Clin Chem. 2003;49(1):144-54. DOI · PubMed