Human chorionic gonadotropin (HCG)
Human chorionic gonadotropin (hCG) is a hormone produced by the placenta during pregnancy, specifically by specialized cells known as syncytiotrophoblasts. It consists of two subunits: an alpha subunit that is shared with other pituitary hormones and a unique beta subunit that gives hCG its specific functions. The primary role of hCG is to support the early stages of pregnancy by maintaining the corpus luteum and ensuring the production of essential hormones until the placenta is fully developed.
hCG is also a key marker in diagnosing gestational trophoblastic disease (GTD), a group of conditions that can lead to tumors such as hydatidiform moles and choriocarcinomas. Elevated hCG levels are commonly seen in patients with GTD, making it an important tool for diagnosis and treatment monitoring. In addition to GTD, hCG levels may indicate other types of tumors, including testicular and germ cell tumors. Due to its significance, both blood and urine tests for hCG are utilized to ensure accurate diagnosis, as several factors can influence hCG levels. Overall, hCG plays a crucial role in reproductive health and cancer diagnostics.
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Human chorionic gonadotropin (HCG)
DEFINITION: The hormone human chorionic gonadotropin (hCG) is secreted by a specialized type of cell (syncytiotrophoblasts) in the developing placenta during embryonic development. hCG comprises alpha and beta subunits found in the blood and urine during a normal pregnancy. The alpha subunit of hCG is shared with the pituitary hormones—follicle-stimulating hormone (FSH), luteinizing hormone (LH), and thyroid-stimulating hormone (TSH). The beta subunit is unique to hCG and determines its functional properties. hCG is needed to maintain pregnancy until the placenta is fully developed. Detection of hCG in the urine is the basis for pregnancy detection kits.
Gestational trophoblastic disease:Gestational trophoblastic disease (GTD) includes several types of tumors, including hydatidiform mole and choriocarcinoma. These tumors develop because of an anomaly in pregnancy when placental (trophoblastic) cells grow out of control. Hydatidiform moles can progress to choriocarcinomas, which are generally aggressive and, if left untreated, widely. hCG is elevated in almost all patients with trophoblastic tumors and is a useful diagnostic marker for monitoring treatment. Gestational trophoblastic disease can be diagnosed and followed by measuring hCG hormone levels in the blood and urine. Ultrasound, computed tomography (CT), positron emission tomography (PET), or magnetic resonance imaging (MRI) scans can also be used to look for tumors. However, when scans show no evidence of tumor presence, hCG levels are often relied on to determine whether the disease may be present.
hCG as a diagnostic marker: Cancer types that may be indicated using hCG levels include seminomas, choriocarcinomas, teratomas, germ cell tumors, hydatidiform moles, islet cell tumors, and testicular cancers. hCG is a diagnostic indicator of tumor formation in gestational trophoblastic disease because of an association between elevated hCG levels and trophoblastic tumors as well as nonseminomatous germ cell tumors (NSGCTs). Trophoblast-derived tumors often secrete only the free beta-hCG subunit. Diagnostic assays specific for the free beta-hCG subunit are most helpful in monitoring tumor development and progression. A negative result is generally less than five million international units/milliliter of beta-hCG in the blood. Gestational trophoblastic disease is treatable, and hCG levels can be used to monitor the success of treatmentas the tumor decreases, so does the level of hCG. Sometimes, elevated hCG levels may be due to factors other than gestational trophoblastic disease. Certain hormones and proteins in the blood may interfere with the blood test results. Therefore, hCG tests should be performed on the blood and urine to diagnose gestational trophoblastic disease.
Bibliography
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