Clinical Significance

Human chorionic gonadotropin (hCG) is a glycoprotein hormone, produced by the placenta, with structural similarity to the pituitary hormones FSH, TSH, and LH. The alpha subunits (MW 15,000-20,000 daltons) are common to all of these hormones but the beta subunits differ, and confer immunological and biological specificity. Beta-hCG (MW 25,000-30,000 daltons) shares several peptide sequences with Beta-LH, but has a unique carboxyl terminal region.

Shortly after implantation of fertilized ovum into the uterine wall, the trophoblast begins to produce hCG, which maintains steroid secretions of corpus luteum until the placentsa can do so. hCG can be detected after implantation; concentrations double approximately every 1.5 to 3 days for the first six weeks and then continue to rise until the end of the first trimester, gradually falling to a lower level for the remainder of the pregnancy. After delivery, hCG returns to <5 mIU/mL (IU/L) and is usually undetectable several days postpartum.

The hormone is an excellent marker for pregnancy. Healthy, non-pregnant individuals have low (<5 mIU/mL [IU/L]) to undetectable hCG levels; however, hCG, originating from the pituitary gland, can be found at detectable levels in periand post-menopausal women. During pregnancy, usually low or rapidly declining levels may indicate an abnormal condition such as an ectopic pregnancy or impending spontaneous abortion.

_{Source: Access Total ßhCG (5^th IS) IFU B29061 B, May 2015}