hCG (HCG) is human hormone made by chorionic cells (in the fetal part of the placenta). hCG is directed at the gonads and stimulates them - hence, the name "gonadotropin.". hCG becomes detectable (by immunologic means) within days of fertilization and forms the foundation of the common pregnancy tests. The level of hcg in maternal serum also enters as one component in the double and the triple screening tests used during pregnancy to assign risks of down syndrome and other fetal disorders.
human chorionic gonadotrophin (hCG) is a glycoprotein produced during pregnancy that is made by the developing embryo after conception and later as part of the placenta. Its role is to prevent the disintegration of the corpus luteum of the ovary and maintain progesterone production that is critical to pregnancy. Progesterone enriches the uterus with a thick lining of blood vessels and capillaries so that it can sustain the growing fetus. hCG may have additional functions; for instance, it is thought that hCG affects the immune tolerance of the fetus repelling the immune cells of the mother and protecting the fetus.
Pregnancy testing, in general, is based on the detection and measurement of hCG. Levels of hCG may be measured in the blood or urine. Early in pregnancy, more accurate results may be obtained by using the first urine of the morning when hCG levels are highest. When the urine is diluted, the hCG concentration may not be representative of the blood concentration, and the test may be falsely negative. As pregnancy tests, quantitative blood tests and the most sensitive urine tests usually detect hCG between 6 to 12 days after ovulation.
Because of its similarity to LH (luteinizing hormone), hCG can also be used clinically to induce ovulation in the ovaries as well as testosterone production in the testes. As the most abundant biological source in women who are presently pregnant, some organizations collect urine from pregnant women to extract hCG for use in fertility treatments. Other forms of hCG are produced through Recombinant DNA (rDNA), a form of artificial DNA that is created through the process of gene splicing.
Last Editorial Review: 9/18/2004
