HUMAN CHORIONIC GONADOTROPHIN

Human chorionic gonadotrophin (HCG) is synthesised early in pregnancy by the newly formed trophoblasts and is secreted into the maternal circulation. It can be detected as early as the eighth day after conception (this property help in quick detection of pregnancy) and its levels in the maternal blood continue to rise rapidly, reaching peak levels at about 10-12 weeks of gestation. HCG measurements have long been used to confirm pregnancy and many "home-test" kits are widely available. Pregnancy kits detecting urine HCG are not as sensitive as those measuring plasma or serum HCG levels the glycoprotein is rapidly metabolised by the liver and kidneys and only a small fraction is excreted unchanged in the maternal urine. HCG has luteotrophic activity and is responsible for maintaining the viability of the corpus luteum into early pregnancy. It may also be responsible for inducing testosterone secretion by the fetal testes before the fetal pituitary is ready to secrete luteinising hormone. Serum HCG titres are also used in the investigation of a probable ectopic pregnancy high titres suggest it as the cause of acute abdominal pain, which is usually the presenting symptom. HCG is also produced by tumours of the trophoblast and thus can occur in males (e.g., testicular teratocarcinoma) and non-pregnant females (e.g., hydatidiform mole and choriocarcinoma).