Human chorionic gonadotropin (hCG): biology, testing, and clinical uses

Structure and physiology

hCG is composed of two noncovalently linked subunits: an alpha subunit that is shared with luteinizing hormone (LH), follicle‑stimulating hormone (FSH) and thyroid‑stimulating hormone (TSH), and a unique beta subunit that confers biological specificity. The hormone is produced by syncytiotrophoblast cells of the developing placenta and acts on LH receptors to maintain the corpus luteum and support progesterone production in early pregnancy.

Detection and interpretation

Clinical testing uses two main approaches: qualitative urine tests (home pregnancy tests) that detect the presence of hCG, and quantitative blood assays that measure the amount of the hormone (usually reported as beta‑hCG). Blood tests are useful for early detection, for following the expected rise in early pregnancy, and for serial measurements when viability or ectopic pregnancy is a concern. In early gestation hCG levels typically rise rapidly and often double every 48–72 hours; they tend to peak in the first trimester and then fall to lower plateau levels for the remainder of pregnancy.

Clinical uses and significance

• Pregnancy detection: home urine tests and laboratory serum assays detect hCG to confirm pregnancy.
• Monitoring pregnancy: serial quantitative measurements can help assess viability or diagnose abnormal implantation (eg, ectopic pregnancy) and gestational trophoblastic disease.
• Fertility medicine: hCG injections are used to trigger ovulation and to support luteal function because of its LH‑like action.
• Oncology: some germ cell tumors and trophoblastic tumors secrete hCG, so it can be a useful tumor marker in diagnosis and follow‑up.
• Other: hCG levels in nonpregnant people can cause false‑positive pregnancy tests and prompt further evaluation.

History and controversies

hCG has been widely used in clinical practice for decades. In contrast, the promotion of hCG for weight loss has been controversial. Products marketed for dieting—often labeled as "homeopathic hCG"—typically contain either highly diluted preparations or no measurable hormone; high‑quality clinical trials have not demonstrated that hCG is effective for weight loss beyond the effects of calorie restriction. Regulatory bodies have acted to restrict misleading marketing of such products; see regulatory guidance and consumer information at related resources.

Notable facts and cautions

Because hCG is structurally related to other pituitary glycoproteins, laboratory assays are designed to detect the beta subunit to improve specificity. Clinicians interpret hCG results in context: a single number has limited meaning, whereas serial trends and clinical assessment are critical. Additionally, hCG has been misused in some contexts (for example, in attempts to influence athletic hormone levels), and such uses are subject to medical and regulatory restrictions. When tests show unexpected hCG positivity in someone who is not pregnant, evaluation for tumor production, heterophile antibodies, or assay interference may be necessary.

For concise official guidance and further reading, consult authoritative resources and local clinical practice guidelines rather than promotional sources.