hCG

Human Chorionic Gonadotropin

Hormones

What is Human Chorionic Gonadotropin?

Human chorionic gonadotropin (hCG) is a glycoprotein hormone composed of an alpha subunit (shared with LH, FSH, and TSH) and a unique beta subunit that confers its biological specificity. hCG is produced primarily by syncytiotrophoblast cells of the placenta after implantation of a fertilized embryo, making it the definitive biochemical marker of pregnancy. Home pregnancy tests and quantitative blood tests both detect hCG, though blood tests are far more sensitive and can detect pregnancy as early as 6–8 days after ovulation.

During early pregnancy, hCG levels approximately double every 48–72 hours, peaking at 8–11 weeks of gestation before declining and plateauing for the remainder of pregnancy. This doubling time is clinically important: normal doubling reassures that the pregnancy is progressing, while abnormal rise patterns may indicate ectopic pregnancy or impending miscarriage. Beyond pregnancy, hCG serves as a tumor marker for gestational trophoblastic disease (molar pregnancy, choriocarcinoma) and certain germ cell tumors of the ovary and testis.

Why It Matters

hCG is essential for confirming and monitoring early pregnancy. Serial hCG measurements help distinguish normal intrauterine pregnancy from ectopic pregnancy and impending miscarriage—conditions that require very different management. In oncology, hCG is a critical tumor marker: it is used to diagnose, stage, monitor treatment response, and detect recurrence of gestational trophoblastic disease and germ cell tumors. Even small elevations of hCG in a non-pregnant individual can signal a serious underlying condition requiring urgent evaluation.

Normal Reference Ranges

GroupRangeUnit
Non-pregnant<5mIU/mL
Pregnancy (4 weeks)5–426mIU/mL
Pregnancy (5–6 weeks)18–7,340mIU/mL
Pregnancy (7–8 weeks)7,650–229,000mIU/mL
Pregnancy (9–12 weeks)25,700–288,000mIU/mL
Second Trimester13,300–254,000mIU/mL
Third Trimester3,640–117,000mIU/mL

Reference ranges may vary by laboratory. Always compare results to the ranges provided by your testing facility.

What High hCG Levels Mean

Common Causes

  • Normal pregnancy (especially multiple gestation—twins, triplets)
  • Molar pregnancy (hydatidiform mole)
  • Choriocarcinoma or gestational trophoblastic neoplasia
  • Germ cell tumors (ovarian or testicular)
  • Down syndrome screening (elevated hCG is a marker)
  • Incorrect gestational dating (earlier than estimated)

Possible Symptoms

  • Severe nausea and vomiting (hyperemesis gravidarum)
  • Vaginal bleeding with abnormally rapid uterine growth (molar pregnancy)
  • Hyperthyroidism symptoms (hCG cross-reacts with TSH receptor)
  • Pelvic mass or testicular mass (germ cell tumors)
  • Often asymptomatic when mildly elevated

What to do: Disproportionately high hCG for gestational age warrants ultrasound to evaluate for molar pregnancy or multiple gestation. A complete molar pregnancy shows a characteristic "snowstorm" pattern on ultrasound with no fetal development and hCG often >100,000 mIU/mL. Treatment is uterine evacuation followed by serial hCG monitoring until undetectable for 6–12 months. Persistent or rising hCG after molar evacuation suggests gestational trophoblastic neoplasia requiring chemotherapy. In non-pregnant individuals, elevated hCG demands imaging of the gonads and potentially the mediastinum and brain to locate a germ cell tumor.

What Low hCG Levels Mean

Common Causes

  • Very early pregnancy (testing before adequate hCG rise)
  • Ectopic pregnancy
  • Impending miscarriage (threatened or missed abortion)
  • Blighted ovum (anembryonic pregnancy)
  • Incorrect gestational dating (later than estimated)

Possible Symptoms

  • Vaginal bleeding or spotting in early pregnancy
  • Abdominal or pelvic pain, especially unilateral (ectopic)
  • Cramping
  • Passage of tissue
  • Absence of expected pregnancy symptoms

What to do: A single low hCG is not diagnostic—serial measurements 48 hours apart are essential. Normal early pregnancy shows hCG doubling every 48–72 hours. A rise of less than 35% in 48 hours is concerning for ectopic pregnancy or non-viable intrauterine pregnancy. A declining hCG usually indicates miscarriage. When hCG reaches the discriminatory zone (1,500–2,000 mIU/mL), transvaginal ultrasound should identify an intrauterine gestational sac; absence of a sac at this level raises strong suspicion for ectopic pregnancy, which may require methotrexate or surgical treatment. Any woman with low or plateauing hCG and abdominal pain needs urgent evaluation to rule out ruptured ectopic pregnancy.

When Is hCG Testing Recommended?

  • To confirm suspected pregnancy
  • When monitoring early pregnancy viability (serial quantitative hCG)
  • When ectopic pregnancy is suspected
  • As a tumor marker for gestational trophoblastic disease or germ cell tumors

Frequently Asked Questions

In a healthy early intrauterine pregnancy, hCG typically doubles every 48–72 hours when levels are below 6,000 mIU/mL. This doubling rate slows as levels rise—above 6,000 mIU/mL, doubling time extends to 72–96 hours. A normal doubling pattern is reassuring but does not guarantee a viable pregnancy, and a slightly slower rise does not necessarily mean the pregnancy is abnormal. However, an hCG rise of less than 35% in 48 hours is concerning and associated with ectopic pregnancy or miscarriage. A decline in hCG indicates a non-viable pregnancy. The doubling time is most useful when combined with ultrasound findings rather than interpreted in isolation.
Yes, and any detectable hCG in a male is abnormal and requires immediate investigation. The most important cause is testicular germ cell tumor—specifically, choriocarcinoma or mixed germ cell tumors that contain trophoblastic elements. Seminomas occasionally produce low levels of hCG. Extragonadal germ cell tumors (mediastinal, retroperitoneal, pineal) can also produce hCG. Rarely, non-germ cell cancers (hepatocellular carcinoma, gastric, lung, bladder) may produce hCG. Testicular ultrasound is the first-line imaging test. Even a small hCG elevation in a man warrants testicular examination and ultrasound. Very rarely, pituitary production of hCG occurs in hypogonadal states.
Implantation typically occurs 6–12 days after ovulation, after which hCG begins to rise. Sensitive blood tests (quantitative serum hCG, detection limit ~1–2 mIU/mL) can detect pregnancy as early as 6–8 days post-ovulation, often before a missed period. Home urine pregnancy tests vary in sensitivity—most detect hCG at 20–25 mIU/mL, which typically corresponds to the day of or 1–2 days after the expected missed period. Some "early detection" home tests claim sensitivity of 6.3–10 mIU/mL. Testing too early increases the risk of a false negative (hCG has not risen enough) or detecting a biochemical pregnancy (very early loss that would have gone unnoticed). For the most reliable result, test on or after the day of the expected period.

Related Biomarkers

P4ProgesteroneE2EstradiolLHLuteinizing HormoneTSHThyroid-Stimulating Hormone

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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Reference ranges may vary between laboratories. Always consult your healthcare provider for interpretation of your specific test results.

Disclaimer: SymptomGPT is not a medical diagnosis tool and does not provide medical advice. Always consult a qualified healthcare professional. If you are experiencing a medical emergency, call 911 immediately.