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Previous research has shown that compared to other heterodimeric glycohormones including follicle-stimulating hormone (FSH), luteinizing hormone (LH), and thyroid-stimulating hormone (TSH), human chorionic gonadotropin (hCG) has a substantially longer half-life. The primary cause is the presence of a CTP in the hCG-subunit (HCG-) that has about 31 amino acids and forms four O-glycosylation sites that end in sialic acid residues. Monosaccharides with a negative charge are sialic acids. Recombinant therapeutic peptides or proteins will have delayed renal clearance and a longer half-life because negatively charged polysaccharides on the glomerular filter membrane will reject them.

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