Elevated serum nicked and urinary beta-core fragment hCG in preeclamptic pregnancies

Thyroid Function and Premature Delivery in TPO Antibody-Negative Women: The Added Value of hCG

CONTEXT

Human chorionic gonadotropin (hCG) stimulates thyroid function during pregnancy. We recently showed that thyroid autoimmunity severely attenuated the thyroidal response to hCG stimulation and that this may underlie the higher risk of premature delivery in thyroperoxidase antibody (TPOAb)-positive women. We hypothesized that a lower thyroidal response to hCG stimulation in TPOAb-negative women is also associated with a higher risk of premature delivery and preterm premature rupture of membranes (pPROM).

DESIGN, SETTING, AND PARTICIPANTS

Thyrotropin (TSH), free thyroxine (FT4), and hCG concentrations were available in 5644 TPOAb-negative women from a prospective cohort. We tested for interaction between TSH or FT4 and hCG in linear regression models for duration of pregnancy and logistic regression models for premature delivery/pPROM. Accordingly, analyses were stratified per TSH percentile (TSH ≥ 85th percentile) and hCG per 10,000 IU/L.

RESULTS

Women with high TSH and low hCG concentrations did not have a higher risk of premature delivery or pPROM, with protective effect estimates. In contrast, women with a high TSH concentration despite a high hCG concentration had twofold to 10-fold higher risk of premature delivery (Pdifference = 0.022) and an up to fourfold higher risk of pPROM (Pdifference = 0.079). hCG concentrations were not associated with premature delivery or pPROM.

CONCLUSION

In TPOAb-negative women with high-normal TSH concentrations, only women with high hCG concentrations had a higher risk of premature delivery or pPROM. These results suggest a lower thyroidal response to hCG stimulation is also associated with premature delivery in TPOAb-negative women and that an additional measurement of hCG may improve thyroid-related risk assessments during pregnancy.

The Risk of Preeclampsia According to High Thyroid Function in Pregnancy Differs by hCG Concentration

CONTEXT

During pregnancy, there is an increased demand for thyroid hormone. The pregnancy hormone human chorionic gonadotropin (hCG) is an important physiological stimulator of thyroid function. Already high-normal maternal free T₄ concentrations are associated with a higher risk of preeclampsia.

OBJECTIVE

The objective of the investigation was to study our hypothesis that hCG concentrations can distinguish a physiological form of high thyroid function from a more pathological form of high thyroid function and that the risk of preeclampsia would differ accordingly.

DESIGN

TSH, free T₄, hCG, or thyroperoxidase antibody concentrations were determined in pregnant women participating in a population-based prospective cohort study.

SETTING

The study was conducted in the general community.

PARTICIPANTS

A nonselected sample of 5146 pregnant women participated in the study.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURE(S)

Preeclampsia was measured.

RESULTS

Women with high hCG-associated high thyroid function did not have a higher risk of preeclampsia than women with normal thyroid function. In contrast, women with low hCG and high thyroid function had a 3.4- to 11.1-fold higher risk of preeclampsia. These risk estimates were amplified in women with a high body mass index. Women with a low hCG and suppressed TSH (<0.10 mU/L) had a 3.2- to 8.9-fold higher risk of preeclampsia. hCG was not associated with preeclampsia, and results remained similar after exclusion of thyroperoxidase antibody-positive women.

CONCLUSION

This study suggests that, in contrast to women with a high hCG associated high thyroid function, women with low hCG and high thyroid function during pregnancy are at a higher risk of developing preeclampsia. The additional measurement of hCG may therefore help to distinguish a more pathological form of high thyroid function and women at a high risk of preeclampsia.

Characterizing urinary hCGβcf patterns during pregnancy

OBJECTIVE

Elevated concentrations of hCG beta core fragment (hCGβcf) are known to cause false-negative results in qualitative urine pregnancy test devices, but the pattern of urinary hCGβcf during normal pregnancy has not been well characterized. Here, we evaluate the relationship between urine hCG, hCGβcf, and hCG free β subunit (hCGβ) during pregnancy.

DESIGN AND METHODS

Banked second trimester urine specimens from 100 pregnant women were screened for high concentrations of hCGβcf using a qualitative point-of-care device known to demonstrate false-negative results in the presence of elevated hCGβcf concentrations. Additional first and third trimester specimens from the same pregnancy were obtained from 10 women who generated negative/faint positive results, 5 women who generated intermediate positive results, and 10 women who generated strong positive results on the point-of-care device. Intact hCG, hCGβcf, hCGβ, and specific gravity were quantified in these 75 specimens.

RESULTS

Urinary hCGβcf concentrations were greater than intact hCG concentrations at all times. A strong correlation (r(2)=0.70) was observed between urine intact hCG and hCGβcf concentrations. A poor correlation was observed between specific gravity and intact hCG (r(2)=0.32), hCGβ (r(2)=0.32), and hCGβcf (r(2)=0.32). The highest hCGβcf concentrations were observed between 10 and 16weeks gestation but individual women demonstrated very different patterns of hCGβcf excretion.

CONCLUSIONS

Urine specimens with elevated hCGβcf are frequently encountered during pregnancy but hCGβcf excretion patterns are unpredictable. Manufacturers and clinicians must appreciate that hCGβcf is the major immunoreactive component in urine during pregnancy and must design and interpret qualitative urine hCG test results accordingly.

The diagnostic significance of hCG and hPL via immunohistochemistry of placental tissues in pregnancies diagnosed with IUGR and IUD

Placentas of patients diagnosed with intrauterine growth restriction (IUGR) and intrauterine death (IUD) were examined by immunohistochemistry for alpha-beta subunits of human chorionic gonadotropin (hCG) and human placental lactogen (hPL) antibodies, and compared with placentas from women with healthy pregnancies. In total, 114 subjects were evaluated. The patient group comprised 27 cases of IUGR and 57 of IUD, and the control group consisted of 30 women with normal pregnancies. Placental specimens were examined for primary antibodies using immunohistochemical techniques. Placentas from 22 cases of IUGR were stained positively for alpha-hCG. All 27 specimens obtained from this group were stained positively for beta-hCG and hPL. Among the cases of IUD, 44 placentas were stained positively for alpha-hCG, and all 57 specimens were stained positively for beta-hCG and hPL.

Can Serum HCG Values Be Used in the Differential Diagnosis of Pregnancy Complicated by Hypertension?

OBJECTIVE

The aim of our study is to determine whether the serum human chorionic gonadotropin (hCG) level is helpful in the differential diagnosis and in the clinical management and follow-up of preeclampsia, superimposed preeclampsia, and chronic hypertension during the third trimester.

MATERIAL AND METHODS

Eighty hypertensive pregnant patients, who had been hospitalized, and 25 normotensive pregnant patients, who attended the outpatient perinatology clinic in Zeynep Kamil Women and Pediatric Diseases Education and Research Hospital between June 2001 and September 2001 were enrolled in the study. These patients were evaluated in five groups: mild preeclamptic, severe preeclamptic, superimposed preeclamptic, chronic hypertensive, and normotensive groups. The geometric means of hCG levels of these groups were compared with each other and cutoff levels for differential diagnosis were determined.

RESULTS

The geometric mean of hCG levels was established as 17,361.31 mIU/mL in the mild preeclamptic group, 49,817.59 mIU/mL in the severe preeclamptic group, 41,101.09 mIU/mL in the superimposed preeclamptic group, 12,558.57 mIU/mL in the chronic hypertensive group, and 9647.98 mIU/mL in the normotensive group. When the geometric mean of the severe preeclamptic group was compared with the results of the normotensive patients, mild preeclamptic patients, chronic hypertensive patients, and superimposed preeclamptic patients, the mean hCG value of severe preeclamptic group was statistically significantly higher than all of the other groups (p < 0.001) except for the latter. The geometric mean of hCG levels of severe preeclamptic patients was compared with the geometric mean of hCG levels of superimposed preeclamptic patients (p > 0.05). The geometric mean of hCG levels in the chronic hypertensive group was lower than that of the superimposed preeclamptic group and the difference was statistically significant (p < 0.001). The geometric mean of hCG levels of the chronic hypertensive group was not significantly different from the results of the mild preeclamptic group and the normotensive group. There was, however, a statistically significant difference between the geometric means of hCG levels of mild preeclamptic patients and normotensive group (p < 0.001). The cutoff value of hCG was determined as 25,000 mIU/mL in differentiation of chronic hypertension from the severe preeclampsia, as 20,000 mIU/mL in differentiation of chronic hypertension from the superimposed preeclampsia, and as 30,000 mIU/mL in differentiation of severe preeclampsia from mild preeclampsia.

CONCLUSION

The maternal serum hCG level is a useful laboratory tool when managing and treating hypertensive disorders that complicate pregnancy. The serum hCG level is especially significant in severe preeclampsia and superimposed preeclampsia. Therefore, a high serum hCG level can be a helpful marker in the diagnosis and clinical management by preventing possible complications resulting from severe and superimposed preeclampsia.

Screening for pre-eclampsia by using maternal serum inhibin A, activin A, human chorionic gonadotropin, unconjugated estriol, and alpha-fetoprotein levels and uterine artery Doppler in the second trimester of pregnancy

AIMS

To analyse the predictive power of maternal serum inhibin A, activin A, human chorionic gonadotropin (hCG), unconjugated estriol (uE(3)), alpha-fetoprotein (AFP) levels and uterine artery Doppler in the second trimester of pregnancy in screening for pre-eclampsia.

METHODS

Maternal serum inhibin A, activin A, hCG, uE(3), and AFP levels and uterine artery Doppler were determined in 178 healthy, pregnant women in the second trimester of pregnancy. Serum samples were collected between the 16th and 18th weeks of gestation, and Doppler investigation was performed between the 24th and 26th weeks of gestation. Receiver operating characteristic curves were created to analyse the predictive powers of the above parameters in screening for pre-eclampsia. Different combinations also were analysed.

RESULTS

The rate of pre-eclampsia was 7.9% (14/178). Maternal serum inhibin A, activin A, hCG, AFP levels, the rate of presence of the prediastolic notch and uterine artery resistance index (RI) values in pre-eclamptic pregnancies were significantly higher than those in healthy pregnancies. Presence of the prediastolic notch, uterine artery RI, maternal serum activin A and inhibin A levels had high predictive efficacy, and each had a sensitivity between 70 and 93% and a specificity between 87% and 98%. The addition of inhibin A or activin A measurement to the Doppler velocimetry improved the specificity to 99-100%.

CONCLUSIONS

Maternal serum inhibin A and activin A levels and uterine artery Doppler appear to be useful screening tests during the second trimester for pre-eclampsia. However, addition of these hormonal markers to Doppler velocimetry only slightly improves the predictive efficacy, which appears clinically insignificant.

Specific Measurement of O-Linked Core 2 Sugar-Containing Isoforms of Hyperglycosylated Human Chorionic Gonadotropin by Antibody B152

There have been a significant number of reports on the clinical utility of measurement of 'hyperglycosylated' isoforms of the pregnancy hormone, human chorionic gonadotropin (hCG). Although there are a variety of hCG isoforms which can be termed 'hyperglycosylated', the measurements were all made using a unique antibody designated B152. This antibody was raised using a choriocarcinoma-derived form of hCG, which was hyperglycosylated with N- and O-glycans and was also 100% 'nicked' hCG. Antibody B152 was recently mapped to a linear epitope around a single O-glycan on the beta-subunit of hCG at residue number 132. Thus, the antibody can only measure isoforms of hCG that possess a core 2 type of branched O-glycan on this portion of the hCG beta-subunit. Isoforms that are hyperglycosylated in the hCG alpha-subunit or only on the N-glycans of hCGbeta will not be recognized by antibody B152. Apparently, measurements of these core 2 hCG isoforms have important clinical application in early pregnancy during which they are the predominant isoform of hCG until the 6th week of gestation. The secretory pattern of these isoforms can be used to predict the health status of the pregnancy in fertility clinics. Moreover, the measurements of these core 2 hCG isoforms are more useful than standard hCG for the prediction of Down syndrome pregnancies. The core 2 isoforms are also of important use in cancer diagnosis and monitoring since their concentration appears to correlate with malignancy.

Predictive value of hormone measurements in maternal and fetal complications of pregnancy

Intrauterine tissues (placenta, amnion, chorion, decidua) express hormones and cytokines that play a decisive role in maternal-fetal physiological interactions. The excessive or deficient release of some placental hormones in association with gestational diseases may reflect an abnormal differentiation of the placenta, an impaired fetal metabolism, or an adaptive response of the feto-placental unit to adverse conditions. This review is focused on the applicability of hormone measurements in the risk assessment, early diagnosis, and management of pregnancies complicated by Down's syndrome, fetal growth restriction, preeclampsia, preterm delivery, and diabetes mellitus. Combined hormonal tests or the combination of hormones and ultrasound may achieve reasonable sensitivity, but research continues to simplify the screening programs without sacrificing their accuracy. Only in a few instances is there sufficient evidence to firmly recommend the routine use of hormone tests to predict maternal and fetal complications, but the judicious use of selected tests may enhance the sensitivity of the risk assessment based solely on clinical and ultrasound examination.

Threading of a glycosylated protein loop through a protein hole: implications for combination of human chorionic gonadotropin subunits

Chorionic gonadotropin (hCG) is a heterodimeric placental glycoprotein hormone essential for human reproduction. Twenty hCG beta-subunit residues, termed the seatbelt, are wrapped around alpha-subunit loop 2 (alpha 2) and their positions "latched" by a disulfide formed by cysteines at the end of the seatbelt (Cys 110) and in the beta-subunit core (Cys 26). This unique arrangement explains the stability of the heterodimer but raises questions as to how the two subunits combine. The seatbelt is latched in the free beta-subunit. If the seatbelt remained latched during the process of subunit combination, formation of the heterodimer would require alpha 2 and its attached oligosaccharide to be threaded through a small beta-subunit hole. The subunits are known to combine during oxidizing conditions in vitro, and studies described here tested the idea that this requires transient disruption of the latch disulfide, possibly as a consequence of the thioredoxin activity reported in hCG. We observed that alkylating agents did not modify either cysteine in the latch disulfide (Cys 26 or Cys 110) during heterodimer formation in several oxidizing conditions and had minimal influence on these cysteines during combination in the presence of mild reductants (1--3 mM beta-mercaptoethanol). Reducing agents appeared to accelerate subunit combination by disrupting a disulfide (Cys 93--Cys 100) that forms a loop within the seatbelt, thereby increasing the size of the beta-subunit hole. We propose a mechanism for hCG assembly in vitro that depends on movements of alpha 2 and the seatbelt and suggest that the process of glycoprotein hormone subunit combination may be useful for studying the movements of loops during protein folding.

Can antenatal clinical and biochemical markers predict the development of severe preeclampsia?

OBJECTIVE

This study was undertaken to develop a multivariable clinical predictive rule for severe preeclampsia using second-trimester clinical factors and biochemical markers.

STUDY DESIGN

We performed a retrospective cohort study of all pregnant patients with single gestations from 1995 through 1997 for whom we had complete follow-up data. Through medical record review we determined whether patients had severe preeclampsia develop according to American College of Obstetricians and Gynecologists criteria. Case patients with severe preeclampsia were compared with control subjects with respect to clinical data and multiple-marker screening test results. With potential predictive factors identified in the bivariate and stratified analyses both an explanatory logistic regression model and a clinical prediction rule were created. Patients were assigned a predictive score according to the presence or absence of predictive factors, and receiver operating characteristic analysis was used to determine the optimal score cutoff point for prediction of severe preeclampsia with maximal sensitivity.

RESULTS

Among the 1998 patients we found 49 patients with severe preeclampsia (prevalence, 2.5%). After we controlled for confounding variables, case patients and control subjects had similar human chorionic gonadotropin and alpha-fetoprotein levels, and the only variables that remained significantly associated with severe preeclampsia were nulliparity (relative risk, 3.8; 95% confidence interval, 1.7-8.3), history of preeclampsia (relative risk, 5.0; 95% confidence interval, 1.7-17.2), elevated screening mean arterial pressure (relative risk, 3.5; 95% confidence interval, 1.7-7.2), and low unconjugated estriol concentration (relative risk, 1.7; 95% confidence interval, 0.9-3.4). Our predictive model for severe preeclampsia, which included only these 4 variables, had a sensitivity of 76% and a specificity of 46%.

CONCLUSION

Even after incorporation of the strongest risk factors, our predictive model had only modest sensitivity and specificity for discrimination of patients at risk for development of severe preeclampsia. The addition of the human chorionic gonadotropin and alpha-fetoprotein biochemical markers did not enhance the model's predictive value for severe preeclampsia.

Evaluation of Nicked Human Chorionic Gonadotropin Content in Clinical Specimens by a Specific Immunometric Assay

We report the development and characterization of an IRMA for the direct measurement of nicked human chorionic gonadotropin (hCGn) in blood and urine. hCGn derived from a reference preparation of hCG used as an immunogen elicits monoclonal antibodies (mAbs) with enhanced recognition of human luteinizing hormone epitopes. The most specific assay for pregnancy hCGn is an IRMA composed of one mAb to choriocarcinoma-derived hCGn (C5) and a second mAb developed from immunization with normal-pregnancy hCGn. This assay was used to evaluate hCGn profiles in normal, in vitro fertilization, Down syndrome, and ectopic pregnancies. In all pregnancies, hCGn was usually present in much lower concentrations than the non-nicked hCG isoform. Our results suggest that some form of physical separation from the overwhelming quantities of non-nicked hCG present in clinical specimens will be required before accurate immunochemical estimations of hCGn can be made.