99-cent-only-store cancer test
99-cent-only-store cancer test
By scott


Newsfeed display by CaRP HCG is a 45 kDa glycoprotein hormone (40 percent carbohydrate) secreted by the syncytiotrophoblastic cells, which form the placenta in the maturing embryo. HCG is normally found in the blood and urine during pregnancy; the rate of secretion rises rapidly following conception, with levels peaking in the first trimester. During this phase, HCG stimulates the corpus luteum to produce the hormones required for maintaining pregnancy. HCG levels then stabilize at lower concentrations for the remaining trimesters and return to nondetectable levels following parturition. The biochemistry and physiology of HCG, as well as the use of HCG determinations for detecting and monitoring pregnancy, are addressed under Pregnancy in the Medical Conditions section of this web site. The focus here is on the role of HCG as a tumor marker.

In the absence of pregnancy, the utility of HCG as a tumor marker derives from the association between elevated HCG levels and trophoblastic tumors (with which levels can be extremely high) and certain tumors of the testes (with which levels are generally more moderately elevated). Other cancers (breast, gastrointestinal tract, lung and ovary) and benign conditions (cirrhosis, duodenal ulcer, and inflammatory bowel disease) may also cause an elevation in HCG levels. HCG determinations by themselves are therefore generally not useful for screening or diagnostic purposes.

Relevant HCG immunoassay characteristics are assay sensitivity-more sensitive assays will be able to detect relapse earlier-and assay specificity. Significant crossreactivity with the closely related pituitary hormones, particularly luteinizing hormone (LH) and follicle-stimulating hormone (FSH), can cause false-positive results. Other specificity considerations include whether the assay recognizes only the intact HCG molecule or whether it also recognizes the presence of the free beta subunit of HCG. [The alpha subunit is shared with the pituitary hormones FSH, LH and thyroid-stimulating hormone (TSH); it is the beta subunit that confers the unique physiological, chemical and physical properties of each of these hormones.]

The ratio of free to intact HCG can be quite high in trophoblastic and certain testicular tumors. Occasionally, such tumors may secrete only the free beta-HCG subunit and virtually no intact HCG at all. Assays that are specific for the free beta-HCG subunit have therefore been found to be useful adjuncts for monitoring and managing these conditions.

Trophoblastic Tumors
Gestational trophoblastic disease, which encompasses a broad spectrum of neoplasms including hydatidiform mole and choriocarcinoma, develops from an aberration in normal pregnancy when trophoblastic cells proliferate abnormally. Hydatidiform moles can progress to choriocarcinomas, which are generally aggressive and, if left untreated, tend to metastasize widely. HCG is elevated in virtually all patients with trophoblastic tumors and is therefore a most useful marker for monitoring treatment and progression. The highest HCG levels correlate with tumor volume; after surgical removal, levels are expected to decrease at a rate that corresponds to the half-life of HCG in serum (12 to 20 hours). More slowly decreasing rates may indicate residual disease. Patient monitoring continues after achieving remission, to detect any relapse.

Testicular Cancer
A variety of different cell types may be involved in the development of germ cell tumors (those that arise from the primordial cells) of the testes. Both AFP and HCG determinations may be used to classify and stage the tumor. The most common testicular malignancies are classified, according to the histological patterns observed, into two major groups: seminomas and nonseminomas. The nonseminomatous group is further classified into terato-, chorio-, and embryonal carcinomas, again based on the hostological elements observed. Both AFP and HCG determinations may be used to classify and stage the tumor. One or both of these markers are elevated in about 90 percent of patients with nonseminomatous testicular tumors, particularly in more advanced cancer stages. Treatment can involve orchiectomy and/or chemotherapy, and the combined use of both markers may be useful for monitoring treated patients. The rate of decrease reflects the effectiveness of the therapy, whereas rising values indicate cancer recurrence or metastasis.

del.icio.us

Rating:


0/5 based on 0 votes. The median rating is 0.

Submitted: 01/15/06

Description: Over the counter pregnancy tests will detect the presence of HCG, a hormone found in two types of people - pregnant women and people with certain types of tumor.

Views: 514 views. Averaging 0 per day.
In the most recent 30 day period, there've been 7 views.

Related Articles:

Previous Article | Next Article

Free Sitemap Generator