Introduction of Human chorionic gonadotropin (HCG) :

Introduction : Human chorionic gonadotrophin (HCG) was the first of the placental protein hormone to be described. It is a member of the glycoprotein hormone family, similar to other pituitary derived hormones like follicle stimulating hormone (FSH), luteinising hormone (LH) and thyroid stimulating hormone (TSH).

Each hormone consists of a non-covalently bound α and β subunits where within a species the α subunit is identical and hormone specifically is determined by unique ẞ subunit.

Functions of Human chorionic gonadotropin (HCG) :

1. It acts as stimulus to sustain the production of progesterone and relaxin by the corpus luteum during luteal phase and the early pregnancy.
2. Through its receptor in endometrium HCG may play a role in the implantation of embryo.
3. HCG may promote smooth muscle relaxation and myometrial vasodilatation.
4. HCG stimulates leydig cells of male foetus to produce testosterone in conjunction with foetal pituitary gonadotrophin It is thus indirectly involved in the development of male external genital organs.
5. It has got immunosuppressive activity which may inhibit the maternal processes of immune rejection of foetus as homograft.
6. It helps in the development of the ovarian hyper-stimulation syndrome in controlled ovarian hyper stimulation.

Causes of high level of HCG :

1. Multiple pregnancies.
2. Hydatidiform mole
3. Gestational choriocarcinoma.
4. Down syndrome (trisomy 21).
5. Germ cell tumour.

HCG assays : HCG is measured in serum or urine by specific radioimmuno-assay technique.

Clinical application of HCG :

1. Trigger ovulation in ovulation induction
2. Oocyte maturation before pickup in assisted reproduction technique
3. Diagnosis of pregnancy
4. Diagnosis of ectopic pregnancy
5. Response to surgical evacuation and chemotherapy in trophoblastic disease.
6. Component of double or triple test in prenatal screening of Down syndrome.
7. Tumour marker for germ cell tumour.
8. Detection of persistent trophoblastic disease.