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The chemical human chorionic gonadotropin (HCG) is produced by trophoblast tissue, which is prevalent in early embryos and will eventually become part of the placenta. Measuring HCG levels can help distinguish between healthy and pathologic pregnancies after an abortion. Screening HCG can help with various tumours, notably choriocarcinoma and extrauterine malignancies. Immunometric assays for HCG are used in serum testing. This implies they sandwich and immobilise the HCG molecules with two antibodies, a fixed antibody and a radiolabeled antibody, which cling to separate places on the molecule.
Epidemiology:
During pregnancy, human chorionic gonadotropin is produced largely by syncytiotrophoblastic cells in the placenta. The hormone stimulates the corpus luteum to generate progesterone to keep the pregnancy going. The pituitary gland, the liver, and the colon all produce smaller HCG levels. Certain cancers can also generate HCG or HCG-related hormones, as previously described. High serum concentrations of HCG-related chemicals are linked to trophoblastic malignancies (choriocarcinoma, hydatidiform mole, and germ cell tumours).
The alpha and beta subunits make up the hormone itself, a glycoprotein. The intact hormone and each unbound subunit can be discovered in various forms in the serum and urine during pregnancy. Although roughly 20% of HCG is eliminated in the urine, it is mostly catabolised by the liver. The beta subunit is broken down in the kidney to form a core fragment detected by HCG testing in the urine.
Clinical Significance:
Human chorionic gonadotropin (HCG) is an important molecule in pregnancy, and its clinical relevance is mostly focused on early diagnosis, serial monitoring throughout pregnancy, and pregnancy-related problems. Women with normal pregnancies have a wide range of HCG levels. In the first trimester of pregnancy, HCG levels in the blood and urine rise dramatically, doubling every 24 hours for the first eight weeks. The peak is normally about ten weeks of pregnancy, after which levels drop until approximately the 16th week of pregnancy when they remain rather stable until term.
Patients with HCG levels that plateau or do not double before eight weeks are likely to have a nonviable pregnancy, whether intrauterine or extrauterine. Extra-uterine (ectopic) pregnancies normally have a slow pace of growth and do not double in size. Due to the wide range of normal hCG levels and the variable rates of rising of this hormone, serum levels are usually checked in conjunction with ultrasound examination to improve sensitivity and specificity.
The time it takes for HCG to return to zero after birth or termination of pregnancy varies from 7 to 60 days. Following the termination of molar pregnancies and the termination of normal or ectopic pregnancies, trending the reduction of HCG levels can be useful in ensuring that the therapy is successful. It’s worth noting that commercial assays use a variety of antibody combinations. This produces heterogeneous results, with immunoassay results varying by up to 50-fold. This is clinically significant, especially when comparing data from laboratories in different facilities/hospitals when looking at low numbers after terminating a pregnancy or trophoblastic illness.
It’s worth noting that commercial assays use a variety of antibody combinations. This produces heterogeneous outcomes, with immunoassay outcomes varying by up to 50-fold. This is clinically significant, especially when comparing laboratory data in various facilities/hospitals when looking at low numbers after terminating a pregnancy or trophoblastic illness.
Full and partial hydatidiform moles, postmolar tumour, gestational choriocarcinoma, testicular choriocarcinoma, and placental site trophoblastic illness can be detected using hCG. These organisms produce HCG, measured at different amounts in commercial tests. A cumulative HCG level of more than 100,000 mIU/mL in early pregnancy, for example, is highly predictive of a full hydatidiform mole, even though many healthy pregnancies reach this value about week 8 to 11 of gestation. Precise HCG readings are critical for determining tumour bulk, cancer treatment efficacy, and testing for disease recurrence or permanence.
In Non-Pregnant women:
In non-pregnant women, HCG levels in the blood rise with age. In women over the age of 55, a cutoff of 14 mIU/mL has been recommended for use in interpreting the data. All nonpregnant patients with good HCG testing should consider testicular cancer, ovarian cancer, bladder cancer or another malignancy.
Conclusion:
A wide spectrum of medical professionals benefits from understanding the utility and variability of different HCG assays. False-positive and false-negative testing has a large impact on patient care. All patient care team members should be aware of frequent testing limitations, such as urine assay false positives due to hematuria, false negatives due to dilute urine, and other less obvious but still important reasons for erroneous testing. Interpreting potentially erroneous results should be done with caution to avoid additional testing and treatment. Good patient care necessitates collaboration, collaborative decision-making and transparency.
