Human chorionic gonadotrophin (hCG) (tumour marker)
Test Background hCG is a sialoglycoprotein hormone with a molecular weight of about 36.5 kDa. hCG, together with LH, FSH and TSH, forms the glycoprotein hormone family, all of which are heterodimers that share a common 92 amino acid α-subunit. The distinct β-subunit confers biological activity and only the intact αβ-heterodimer of hCG can stimulate sex steroid production through the LH/hCG G-protein-coupled receptor. hCG is secreted by the trophoblastic placental cells and a variety of tumours. However, tiny amounts are also produced by the pituitary. hCG exists not only as the intact heterodimer but also as free subunits and an array of molecular variants that are recognised by different hCG assays to a variable degree. The hCG tumour marker assay we provide is a ‘total’ hCG assay that recognises all forms for which WHO protein standards have been formulated, and is used for the management of germ cell tumour (GCT) and gestational trophoblastic disease (GTD).
Clinical IndicationsDiagnosis: hCG measurement is used in the diagnosis of GTD and GCT. hCG measurement is the basis of post-molar screening for gestational trophoblastic neoplasia (GTN). CSF measurement is helpful in diagnosis of primary intracranial GCT and detecting metastatic spread to the brain in GTN. Prognosis and staging: hCG is used for risk stratification and treatment decision making in GTN and GCT. Treatment monitoring: response to treatment in GTN and GTD is monitored using 1-2 weekly hCG measurements. Surveillance: in GCT, serial monitoring with hCG (and AFP) at decreasing frequency for a minimum of 10 years is used in both marker positive and negative disease. Following treatment for GTN, hCG is monitored for life.