beta-hCG Concentrations Research Articles

Response of human chorionic gonadotrophin to luteinizing hormone-releasing hormone stimulation in the culture media of normal human placenta, choriocarcinoma cell lines, and in the serum of patients with gestational trophoblastic disease.

In vitro and in vivo responses to luteinizing hormone-releasing hormone (LHRH) stimulation of human chorionic gonadotrophin (hCG) production were evaluated. We cultured placental tissues of ten weeks and term pregnancy, choriocarcinoma tissues, and monolayers of the BeWo cell line, and added serial dilutions of LHRH (1, 5 and 10 micrograms) to the media for five to seven days. In in vivo experiments, 100 micrograms LHRH was intravenously administered to 20 normally cycling women (control group), 27 women who were 'possible remission', and 21 women with 'minimal resistance' to gestational trophoblastic disease. After injection of LHRH, blood samples were collected at 0, 30, 60, 90 and 120 minutes. The concentrations of immunoreactive beta-hCG in in vitro culture media, and in sera from patients, were measured before and after LHRH stimulation by double-antibody radioimmunoassay. These in vitro and in vivo experiments revealed that normal and malignant trophoblastic cells responded to the LHRH stimulation by producing immunoreactive beta-hCG. Therefore, LHRH stimulation may be useful in detecting residual choriocarcinoma cells in gestational trophoblastic disease patients during their periremission periods.

Doubling time of human chorionic gonadotropin (hCG) in early normal pregnancy: relationship to hCG concentration and gestational age

There is controversy regarding whether the doubling time of human chorionic gonadotropin (hCG) in early normal pregnancy is constant or rises with increasing gestational age (GA) and hCG concentration. To clarify the influence of these variables on hCG doubling time, we obtained serial blood specimens every 2 to 4 days between postovulatory day 12 and 70 from 16 women who conceived while monitoring basal body temperature. The serum concentration of beta-hCG was determined by radioimmunoassay. Serial doubling time of hCG was calculated in all subjects and correlated with GA and hCG concentration. Least-squares estimates of 95% confidence bands were established from regression analysis given the second hCG concentration for each pair of samples or GA. For elimination of the need for calculation and thus improvement of the clinical utility of doubling time determinations, a nomogram relating the concentrations of hCG in paired serum samples to doubling time was constructed. We observed a significant correlation of doubling time with hCG concentration and GA, both in the group overall and within each individual pregnancy. These data support the recommendation that doubling time determinations should be evaluated with reference to normal values for a given GA or hCG concentration and suggest that previously proposed normal values of doubling time in early normal pregnancy may be low.

Radioimmunoassay of the Serum Freeβ-Subunit of Human Chorionic Gonadotropin in Trophoblastic Disease*

We developed a RIA specific for the free beta hCG employing anti-beta hCG monoclonal antibody 1D12. This RIA was highly sensitive to free beta hCG; the minimum detectable concentration was 0.4 ng/ml. alpha hCG, LH, beta LH, and FSH had little effect in the assay; the cross-reactivity of hCG was about 4%. Using this RIA, we measured serum free beta hCG concentrations in 38 normal pregnant women and 72 untreated patients with 3 types of trophoblastic disease: hydatidiform mole (n = 15), invasive mole (n = 29), and choriocarcinoma (n = 28). All of these samples were simultaneously assayed for hCG by RIA. In normal pregnant women, serum hCG changed as pregnancy progressed, but serum free beta hCG was not detected at any time. In contrast, serum free beta hCG was measurable in the majority of patients with trophoblastic disease. Strong correlations were found between the concentration of free beta hCG and that of hCG in each type of trophoblastic diseases. The mean free beta hCG to hCG ratio was lowest for hydatidiform mole and highest for choriocarcinoma, and the difference between the ratios in these 2 groups was statistically significant. Serial measurements in 7 patients with trophoblastic disease failed to reveal remarkable changes in the free beta hCG to hCG ratio throughout their clinical course. We conclude that the production of free beta hCG increases with the immaturity of the trophoblastic cell, and the degree of differentiation of trophoblastic cells may be reflected by the free beta hCG to hCG ratio.

Physiological Studies of Human Chorionic Gonadotropin (hCG), αhCG, and βhCG as Measured by Specific Monoclonal Immunoradiometric Assays*

Several libraries of monoclonal antibodies have been produced against epitopes that reside on hCG, alpha hCG, and beta hCG. Having characterized them physically, we explored their use in the construction of highly specific and sensitive immunoradiometric assays. There were several important immunochemical considerations with respect to developing assays that accurately detect low levels of free subunits in serum in the presence of high concentrations of the native hormone. These include physical properties and specificities of the monoclonal antibodies, choice of capture antibody on the solid phase support, assay design, and purity of hormone standards. Using such assays, we found early pregnancy (in vitro fertilization) to be characterized by the sequential appearance of hCG, followed by beta hCG and then alpha hCG. Molar ratios of beta hCG to alpha hCG and beta hCG to hCG were highest in early gestation. However, there was a reversal of the beta hCG to alpha hCG ratio at 12-13 weeks gestation, and an excess of free alpha hCG was observed thereafter. Except for values obtained in very early pregnancy, the beta hCG to hCG ratio remained remarkably constant at approximately 0.5% throughout gestation. In contrast, choriocarcinoma was distinguished by absolute serum beta hCG concentrations 3-100 times greater than the maximum values observed during pregnancy and, more importantly, by exceedingly high beta hCG to hCG ratios. For comparison, we studied hCG, alpha hCG, and beta hCG levels in an additional 178 patients with nontrophoblastic tumors. Ectopic production of alpha hCG and beta hCG was rare (3%), and thus far, we have been unable to demonstrate the presence of hCG in such patients. Therefore, hCG and the free subunits appear not to be useful as serological markers for nontrophoblastic tumors.

Progesterone dependence and extratrophoblastic origin of pregnancy-associated plasma protein-A (PAPP-A) in early pregnancy

Pregnancy-associated plasma protein-A (PAPP-A) is a macromolecular glycoprotein produced in increasing concentration as pregnancy advances. PAPP-A is not specific to pregnancy since measurable levels have been found in non-pregnant females and in males. In non-pregnant females, PAPP-A is probably produced by the endometrium. The origin of PAPP-A in pregnant women is still controversial. In-vitro trophoblast and decidual explants both produce PAPP-A. So far, it is not known if the same applies to the in-vivo situation and to what extent these two tissues contribute to the circulating levels of PAPP-A. This study compares the circulating concentrations of PAPP-A and beta-hCG and progesterone in different pathological situations. In hydatidiform moles, beta-hCG levels are very high demonstrating an intense trophoblastic activity, whereas PAPP-A levels remain in the normal range. With spontaneous abortions, beta-hCG levels decline to very low values whereas PAPP-A continues to increase. These observations furnish indirect evidence for a major contribution to circulating PAPP-A levels by extratrophoblastic sites. Furthermore, PAPP-A levels decrease after administration of an anti-progesterone (RU486) either in-vivo or in-vitro. This is considered as a proof that PAPP-A levels in early pregnancy are progesterone dependent.

Ectopic Pregnancy

The diagnosis of ectopic pregnancy has become precise and reliable. Consequently, the management of ectopic pregnancy has progressed to the point where the physician is often able to preserve fertility. Therefore, conservative surgery is indicated if the patient desires future fertility and conditions are appropriate. The combination of ultrasound, beta-hCG pregnancy testing, and laparoscopy has led to a rising incidence of diagnosed ectopic pregnancy prior to rupture. This has greatly facilitated the use of the conservative approach to the management of tubal pregnancy. Although ectopic pregnancy can be diagnosed early and managed conservatively, it is, and will remain a potentially life-threatening disease and must be approached as such. Table 3 summarizes our proposed surgical management of tubal pregnancy. Table 4 summarizes the results of conservative surgery for tubal pregnancy.

THE DISAPPEARANCE OF HUMAN CHORIONIC GONADOTROPIN FROM PLASMA AND URINE FOLLOWING INDUCED ABORTION

In 28 females, daily measurement of the HCG concentration in urine and in 15 of them daily measurement of the beta-HCG concentration in plasma was carried out during the first 2 weeks following first-trimester induced abortion by vacuum aspiration. Plasma beta-HCG concentration fell according to a multi-exponential curve with a half-life of 0.63 days in the first 2 days following induced abortion, and of 3.85 days in the subsequent 14 days. The disappearance of HCG from urine is exponential, with a half-life value of 1.3 days. A urine pregnancy test with a sensitivity of 1 IU/ml wil nearly always be negative in the course of 2 weeks after abortion. A positive test 4 weeks after abortion indicates an incomplete abortion or persistent trophoblast.

An evaluation of four serum tests for pregnancy.

We evaluated four pregnancy tests (Biocept-G, Beta-CG, Preg/Stat, and HCG-Beta Screen), using sera from 59 nonpregnant subjects and 77 patients with serum human choriogonadotropin beta-subunit (beta-hCG) concentrations ranging from 4 to 100 000 int. units/L. The results obtained for each test were compared with the results predicted on the basis of the sample's beta-hCG concentration and the beta-hCG concentration the manufacturer claimed necessary for a positive result (the test's analytical sensitivity). Biocept-G had the best sensitivity (100%), specificity (98.9%), and accuracy (99.2%). Beta-CG had the poorest sensitivity (86.4%), Preg/Stat the poorest specificity (87.5%), and accuracy (92.6%). We confirmed the manufacturer's claimed analytical sensitivity (200 int. units/L) for the Biocept-G procedure, but our calculated analytical sensitivity for the other tests was significantly different from that claimed by their manufacturers. Best results were obtained with Biocept-G, but with its analytical sensitivity of 200 int. units/L, samples from early pregnancy will give negative results. None of the pregnancy tests evaluated here will establish the presence or absence of early pregnancy with certainty.

Concentrations of SP1 and beta-hCG in serum and cerebrospinal fluid and concentrations of hCG in urine in patients with trophoblastic tumour.

Using immunological techniques urinary hCG, pregnancy-specific beta 1-glycoprotein (SP1) and beta-subunit of hCG (beta-hCG) levels were measured in the serum and cerebrospinal fluid of patients with trophoblastic tumours. After removal of hydatidiform moles, urinary hCG, beta-hCG and SP1 levels were similar, but SP1 levels tended to exceed serum beta-hCG levels. SP1 usually disappeared first. In patients with metastatic choriocarcinoma, SP1 levels appeared to be lower than beta-hCG values in serum and cerebrospinal fluid, but urinary hCG, beta-hCG and SP1 concentrations all decreased during chemotherapy. Measurements of SP1 levels may well be useful in the monitoring of patients being treated for trophoblastic tumours.

SP-1 and beta-HCG in suspected ectopic pregnancy (author's transl)

Serum levels of SP-1 and beta HCG as Trophoblastic Markers were measured in 31 women operated on suspected ectopic pregnancy. In all 24 patients with tubal pregnancy SP-1 levels estimated by enzyme immunoassay Enzygnost were higher than 5 ng/ml, whereas SP-1 levels in 7 cases with benign ovarian cysts were less than 2 ng/ml. Beta-HCG in serum was analysed by radioimmunoassay (Serono-Biodata): in cases with ectopic pregnancy serum levels were between 113 mIU/ml and 1040 mIU/ml, in the 7 nonpregnant cases the highest concentration was 7 mIU/ml. There was no correlation between serum concentration of SP-1 and beta-HCG (r = 0,571). In view of clinical practice preference is given to estimation of SP-1 by enzyme immunoassay over estimation of beta-HCG by radioimmunoassay, the reasons are discussed.