A gonadotropin secreted by the developing placenta and by the fertilized egg after implantation in the uterine wall
Human chorionic gonadotropin (hCG) is a glycoprotein hormone. It consists of 237 amino acid units and has a molecular mass of 36.7 kDa. It occurs as a heterodimer. It has an alpha subunit and beta subunit. Similar to other gonadotropins, the alpha subunit is made up of 92 amino acids. The beta subunit of gonadotropins sets them apart from each other. In hCG, the beta subunit is comprised of 145 amino acids.
hCG is a gonadotropin produced and released by developing placenta as well as by the fertilized eff after implanting in the uterine wall. It is also produced by certain cancerous tumors. In the placenta, the syncytiotrophoblasts are the cells producing hCG. hCG interacts with the LHCG receptor on the target cells in the ovary. It is essential primarily in preventing the breakdown of the corpus luteum. This enables the corpus luteum to secrete progesterone during the first trimester. Progesterone is essential as it acts by enriching the uterus with a thick ling of blood vessels and capillaries that would sustain the growing fetus.
hCG is measured in the blood to determine pregnancy. It increases in quantity through the first trimester of pregnancy, and then begins to taper off after 85 days.
Serum human chorionic gonadotrophin testing is accurate 48 hour post conception. Urine human chorionic gonadotrophin testing is a popular method of home pregnancy determination as hCG can be detected in urine.
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