Beta-hCG

Beta-hCG

Beta-hCG (beta-human chorionic gonadotropin) is a subunit of the hormone human chorionic gonadotropin (hCG), which is produced by the placenta during pregnancy. It is a glycoprotein hormone that plays a crucial role in the maintenance of the corpus luteum during the early stages of pregnancy. The presence of beta-hCG is the basis for most pregnancy tests.

Structure

Beta-hCG is composed of 145 amino acids and has a molecular weight of approximately 22,200 daltons. It is one of the two subunits of hCG, the other being the alpha subunit. The alpha subunit is common to other hormones such as luteinizing hormone (LH), follicle-stimulating hormone (FSH), and thyroid-stimulating hormone (TSH), while the beta subunit is unique to hCG, providing its specific biological activity.

Function

The primary function of beta-hCG is to support the corpus luteum in the ovary, which in turn produces progesterone during the first trimester of pregnancy. Progesterone is essential for maintaining the uterine lining and providing a suitable environment for the developing embryo. Beta-hCG also plays a role in the development of fetal organs and the modulation of the maternal immune response to allow for the acceptance of the pregnancy.

Clinical Significance

Beta-hCG is a critical marker in both pregnancy and certain medical conditions. It is used in:

• Pregnancy Testing: Beta-hCG is detected in the blood and urine of pregnant women. Home pregnancy tests and clinical tests measure the levels of beta-hCG to confirm pregnancy.
• Monitoring Pregnancy: Quantitative beta-hCG tests can help monitor the progress of a pregnancy, especially in the early stages. Abnormal levels can indicate potential issues such as ectopic pregnancy or miscarriage.
• Cancer Marker: Elevated levels of beta-hCG can be associated with certain types of cancer, such as choriocarcinoma, testicular cancer, and gestational trophoblastic disease.

Measurement

Beta-hCG levels can be measured through blood tests or urine tests. Blood tests are more sensitive and can detect lower levels of the hormone, making them useful for early detection of pregnancy and monitoring of hCG levels in various clinical scenarios.

Also see

• Human chorionic gonadotropin
• Pregnancy test
• Gestational trophoblastic disease
• Choriocarcinoma
• Ectopic pregnancy