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Beta-human chorionic gonadotropin (β-hCG)

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Beta-human chorionic gonadotropin (β-hCG) is a specific pregnancy hormone synthesized by trophoblast cells after embryo implantation.

  • Detectable in blood 6–8 days post-fertilization, making it one of the earliest markers of pregnancy.
  • In urine, β-hCG reaches detectable levels1–2 days after appearing in plasma, which is why urine pregnancy tests are slightly less sensitive than blood tests.

    Role of Beta-hCG in Pregnancy

  • During the first trimester, β-hCG maintains corpus luteum function, ensuring the production of progesterone and estrogens.
  • This process continues until the placenta fully takes over hormone production.
  • In male fetuses, β-hCG stimulates Leydig cells to produce testosterone, which is essential for male reproductive development.
  • Peak β-hCG levels occur around 10–11 weeks of pregnancy, then gradually decline.
  • In multiple pregnancies, β-hCG levels are proportionally higher due to the presence of multiple embryos.
  • The test is performed on a venous blood sample.
  • Fasting (8–14 hours) is required, but water intake is allowed.
  • The test can also be taken 4 hours after a light meal.
  • Avoid physical and emotional stress, as well as alcohol, before testing.

In Women:

  • Amenorrhea (absence of menstruation)
  • Early pregnancy detection
  • Suspected ectopic pregnancy
  • Pregnancy monitoring (hCG dynamics)
  • Diagnosis of trophoblastic diseases (e.g., choriocarcinoma, hydatidiform mole)
  • Monitoring the effectiveness of treatment for trophoblastic diseases
  • Prenatal screening for fetal abnormalities

In Men:

  • Differential diagnosis of testicular tumors

Causes of Increased Beta-hCG Levels

In Men and Non-Pregnant Women:

  • Choriocarcinoma (gestational trophoblastic disease)
  • Seminoma (testicular cancer)
  • Testicular teratoma
  • hCG-producing gastrointestinal tumors
  • Recent abortion (hCG remains elevated for 4–5 days after termination)
  • hCG medication use (e.g., in fertility treatments)

In Pregnant Women:

  • Multiple pregnancy
  • Mismatch between expected and actual gestational age
  • Severe pregnancy toxicosis or preeclampsia
  • Maternal diabetes
  • Chromosomal abnormalities in the fetus (e.g., Down syndrome, Edwards syndrome)
  • Synthetic progestin use
     

    Causes of Decreased Beta-hCG Levels

    In Pregnant Women:

  • Lower-than-expected β-hCG levels (delayed rise or insufficient increase of more than 50%)
  • Ectopic pregnancy
  • Missed miscarriage (early pregnancy loss)
  • Risk of spontaneous abortion (miscarriage)
  • Chronic placental insufficiency
  • Intrauterine fetal death (2nd or 3rd trimester)
     

    False-Negative Beta-hCG Results (No Detectable Increase During Pregnancy)

  • Test performed too early (before β-hCG reaches detectable levels in blood/urine)
  • Ectopic pregnancy (hCG levels rise slower than in normal pregnancy)