What Is hCG? Human Chorionic Gonadotropin Explained
Hormones
hCG (human chorionic gonadotropin) is a glycoprotein hormone made by the placenta during pregnancy, and it is the hormone that standard pregnancy tests detect. It is also a licensed medicine for a few specific medical uses, and it is widely discussed online as a weight-loss aid, a use the US prescribing label says has not been demonstrated.
What is hCG (human chorionic gonadotropin)?
hCG is a protein hormone built from two chains. According to UniProt, its beta chain is highly expressed in the placenta throughout pregnancy, where it helps the ovaries keep making the steroid hormones needed to maintain the pregnancy. Outside pregnancy, hCG is normally not present at meaningful levels, which is why detecting it is a useful sign of pregnancy.
The US prescribing label for the hCG product Novarel describes the drug as a water-soluble glycoprotein derived from human pregnancy urine. That tells you two things: hCG carries sugar chains (it is a glycoprotein), and it is a large protein rather than a short peptide of a few amino acids.
How hCG is built: a shared alpha chain and its own beta chain
hCG belongs to the glycoprotein hormone family, together with thyrotropin (TSH), lutropin (LH) and follitropin (FSH). UniProt describes the common alpha chain as 92 amino acids in its mature form, shared by all four hormones. What makes each hormone different is its beta chain. For hCG the mature beta chain is 145 amino acids long (UniProt entry P0DN86, choriogonadotropin subunit beta 3).
Because hCG and LH are so closely related, they are recognized by the same receptor, the luteinizing hormone/choriogonadotropin receptor. That overlap is why hCG can stand in for LH in some medical settings.
hCG also exists in several glycosylation variants. Reviews describe a form called hyperglycosylated hCG that is made early in pregnancy, and one study reported it as a marker of early trophoblast invasion. These variants matter mainly to laboratory medicine and pregnancy research.
What hCG does in pregnancy
After implantation, the placenta-derived trophoblast cells secrete hCG. In the UniProt summary, the hormone has an essential role in pregnancy and maternal adaptation and stimulates the ovaries to produce the steroids that sustain the pregnancy. This is the core biology behind both home pregnancy tests and the clinical use of hCG in fertility care.
Medical uses of hCG on the US label
The Novarel prescribing information lists three indications: prepubertal cryptorchidism not due to anatomic obstruction; selected cases of hypogonadotropic hypogonadism (hypogonadism secondary to a pituitary deficiency) in males; and induction of ovulation and pregnancy in selected anovulatory, infertile women. The label also lists contraindications that include precocious puberty, prostatic carcinoma or other androgen-dependent neoplasm, and a prior allergic reaction to hCG.
hCG and weight loss: what the evidence shows
hCG became popular in diet programs decades ago, so the question has been studied. A 1995 criteria-based meta-analysis in the British Journal of Clinical Pharmacology (Lijesen et al.) traced eight controlled and 16 uncontrolled trials. Methodological quality scores ranged from 16 to 73 out of 100, so most studies were of poor quality. Of the 12 studies scoring 50 or more, one reported hCG as a useful adjunct. The authors concluded there is no scientific evidence that hCG is effective in treating obesity, and that it does not produce weight loss, fat redistribution, less hunger or a feeling of well-being.
The prescribing label says the same thing in plain terms: hCG has not been demonstrated to be effective adjunctive therapy in the treatment of obesity, and there is no substantial evidence that it increases weight loss beyond that resulting from caloric restriction.
Quality and safety considerations
hCG products are injectable biologic-type medicines, so sterility matters. A conference abstract in Open Forum Infectious Diseases (2018) described an outbreak of Mycobacterium chelonae skin infections associated with hCG injections at weight-loss clinics, a reminder that injectables prepared or handled outside proper controls can carry real infection risk. For how purity and contaminants are assessed in general, see the related reading below.
Because hCG is a prescription hormone with a defined label, questions about whether it is appropriate for any individual belong with a licensed clinician.
Frequently asked questions
Is hCG the same as LH?
No, but they are close relatives. Both share the same alpha chain and act on the same receptor, while their beta chains differ.
Why do pregnancy tests detect hCG?
Because the placenta makes it during pregnancy, while it is normally absent otherwise, making it a convenient marker.
Does the hCG diet work?
The label and the best-known meta-analysis both say there is no demonstrated benefit beyond calorie restriction.
Is hCG a peptide?
It is a protein hormone made of two chains (92 and 145 amino acids), so it is larger than the short peptides usually discussed in this field.
References
- UniProt P01215: Glycoprotein hormones alpha chain
- UniProt P0DN86: Choriogonadotropin subunit beta 3
- Novarel (chorionic gonadotropin for injection) prescribing information
- Lijesen GK et al. The effect of HCG in the treatment of obesity by means of the Simeons therapy: a criteria-based meta-analysis. Br J Clin Pharmacol 1995
- Cole LA. Hyperglycosylated hCG, a review. Placenta 2010
- Guibourdenche J et al. Hyperglycosylated hCG is a marker of early human trophoblast invasion. J Clin Endocrinol Metab 2010
Informational only — not medical advice. This article is for educational purposes. It does not recommend, sell or instruct personal human use of any compound. Consult a qualified healthcare professional for any health decision. Content is intended for adults 21+. Verify scientific details against the primary sources cited.