hCG Peak Research Articles

Characterization of a small immunoreactive HCG-like component isolated from urine of a patient with choriocarcinoma.

An immunoreactive hCG-like substance with low molecular weight was isolated from the urine of a patient with choriocarcinoma and its characteristic properties were studied. The urinary hCG preparation was fractionated by gel filtration on a Sephadex G75 column and each fraction was assayed for hCG activities by an enzyme linked immunosorbent assay using a monoclonal antibody to hCG (Mab-5D4). Two immunoreactive hCG peaks were obtained. One was coeluted with ordinary hCG and the other was eluted after hCG-alpha. After refractionation on the same column, the hCG peak (Ag-2) with low molecular weight was radioiodinated with 125INA and applied to an immunoaffinity column bound Mab-5D4 for further purification. The purified 125I-labelled Ag-2 showed a high binding activity to a conventional rabbit anti-hCG serum and Mab-5D4. This Mab had binding specificity to hCG, hCG-beta and LH but not to hCG-alpha. However, this fraction did not bind to Mab-6E4 which possessed binding activities only to hCG, hCG-alpha and LH, nor to Mab-2F8 which was specific only to hCG. Autoradiography after SDS-Page of the immune precipitate which was made by 125I-labelled Ag-2 and Mab-5D4, revealed that the Ag-2 had a molecular weight of approximately 14,000 daltons. Lectin (LeH) affinity chromatography of the urinary hCG specimen from the same patient revealed that it contained two kinds of immunoreactive hCG. One did not bind to LeH column but the other did. A small immunoreactive molecule (Ag-2) was detected in the LeH-unbound fraction but not in the LeH-bound fraction. These results suggest that choriocarcinoma patients excrete in the urine a small LeH-unbound immunoreactive component which contains an antigen epitope common to hCG, hCG-beta and LH.

Physiological and pathological aspects of the effect of human chorionic gonadotropin on the thyroid.

Human chorionic gonadotropin (hCG) is a glycoprotein hormone that has structural similarity to TSH. At the time of the peak hCG levels in normal pregnancy, serum TSH levels fall and bear a mirror image to the hCG peak. This reduction in TSH suggests that hCG causes an increased secretion of T4 and T3. Women with hyperemisis gravidarum often have high hCG levels that cause transient hyperthyroidsm. In the vast majority of such patients, there will be spontaneous remission of the increased thyroid function when the vomiting stops in several weeks. When there are clinical features of hyperthyroidism, it is be reasonable to treat with antithyroid drugs or a beta-adrenergic blocker, but treatment is rarely required beyond 22 weeks of gestation. Hyperthyroidism or increased thyroid function has been reported in many patients with trophoblastic tumors, either hydatiditform mole or choriocarcinoma. The diagnosis of hydatidiform mole is made by ultrasonography that shows a 'snowstorm' appearance without a fetus. Hydatidiform moles secrete large amounts of hCG proportional to the mass of the tumor. The development of hyperthyroidism requires hCG levels of >200 U/ml that are sustained for several weeks. Removal of the mole cures the hyperthyroidism. There have been many case reports of hyperthyroidism in women with choriocarcinoma and high hCG levels. The principal therapy is chemotherapy, usually given at a specialized center. With effective chemotherapy, long-term survival exceeds 95%. A unique family with recurrent gestational hyperthyroidism associated with hyperemesis gravidarum was found to have a mutation in the extracellular domain of the TSH receptor that made it responsive to normal levels of hCG.

Physiopathologie de l’hormone chorionique gonadotrope humaine (hCG) dans la trisomie 21 fœtale

The reason why maternal serum hCG is increased the second trimester of trisomy 21 associated pregnancy, is still unclear. It results from the placental immaturity which affects the differenciation of cytotrophoblasts into the endocrine syncytiotrophoblast. During the second half of the gestation, the hCG production rate could be comparable as those observed during the first trimester. The physiological peak of hCG could be delayed from the first to the second trimester. hCG could be highly glycosylated and thus its half life would be modified.

Dimeric inhibin A and alpha-subunit immunoreactive material in maternal serum during spontaneous and in vitro fertilization pregnancies.

To increase our understanding of the nature and source of immunoreactive inhibin-related material during pregnancy, we studied inhibin secretion in women pregnant after spontaneous conception and after in vitro fertilization (IVF). Two solid phase enzyme-amplified immunoassays (EASIAs) were used to measure the inhibin A dimer and inhibin alpha-subunit immunoreactivities (alpha-inhibin). In spontaneous pregnancies, levels of both inhibin A and alpha-inhibin were low during the first two trimesters of pregnancy, but a significant increase was observed toward the end of gestation. Both assays confirmed that inhibin concentrations in IVF pregnancies exceeded those in spontaneous pregnancies during the entire first trimester. Moreover, the two assays displayed discordant profiles. The alpha alpha-EASIA, which detects all alpha-inhibin immunoactivity, displayed a major peak during the follicular phase and a second broader peak during the luteal phase and corpus luteum rescue. A progressive decline was observed during the subsequent weeks. EASIA measurements for inhibin A revealed distinct peaks during the follicular phase, the luteal phase, and the hCG peak. A marked fall, however, was seen at the time of corpus luteum rescue. In summary, these data indicate that the nature of the immunoreactive material changes considerably during the different phases of pregnancy. The available evidence further points to an ovarian source of dimeric inhibin in early pregnancy and a placental source toward the end of pregnancy.

The deactivation of hCG by nicking and dissociation.

Human chorionic gonadotropin (hCG) is composed of an alpha- and a beta-subunit, joined noncovalently. A proportion of hCG molecules in pregnancy serum and urine samples have nicks or a missing peptide linkage between either beta-subunit residues 44 and 45 or beta-subunit residues 47 and 48. These nicks ablate the steroidogenic activity of hCG. We examined the source of nicking, and the occurrence and stability of nicked hCG molecules produced during pregnancy. We investigated the source of nicking. Standard hCG was added to three samples of whole blood, and incubated 18 h at 37 C. No change in extent of nicking was detected. However, nicking of hCG beta-subunit was detected by gel electrophoresis (bands at M(r) = 17,000 and M(r) = 22,000, corresponding to the peptides beta 1-47(44) and beta 48(45)-145, respectively) in culture fluids from first trimester placental explants and from JAr malignant trophoblast cells. We inferred that nicking occurs before or immediately upon secretion by trophoblast tissue. We examined the occurrence of nicking. Levels of total hCG (nicked+nonnicked) and intact hCG (nonnicked) were determined in 233 serum and 168 urine samples from 4-40 weeks of pregnancy. From the two measurements the extent of nicking was estimated. A linear relationship was indicated between advancing weeks of gestation and increasing extent of nicking (regression analysis, months vs. percent nicked, 95% correlation). Minimum nicking was observed in serum from the first 2 months of pregnancy (mean = 9% of hCG molecules), increased nicking in the months after, and maximum nicking in samples from the last 2 months of pregnancy (mean = 21% of hCG molecules, t test first 2 months vs. last 2 months, P < 0.00005). Similar results were observed with urine samples (first 2 months mean = 9%, last 2 months = 27%, t test P < 0.00005). We concluded that nicking is more prevalent after the hCG peak (after 2 months of pregnancy). Finally, we examined the stabilities of nicked and intact hCG molecules. Standard hCG (batch CR127, 20% nicked) and hCG preparation C5 (100% nicked) were incubated for varying times in whole blood. C5 hCG dissociated rapidly into free alpha- and beta-subunits (dissociation half-life 22 +/- 5.2 h), over 30 times faster than standard hCG (dissociation half-life 700 h).(ABSTRACT TRUNCATED AT 400 WORDS)

The 24-Hour Pattern of the Levels of Serum Progesterone and Immunoreactive Human Chorionic Gonadotropin in Normal Early Pregnancy*

The purpose of this study was to characterize the levels of progesterone and hCG and the variability of those levels over 24 h in early pregnancy. Venous blood sampling was performed every 30 min during the first trimester of a subsequently normal pregnancy in 19 women. The variability in each progesterone and hCG data series was evaluated by three methods: 1) comparing the coefficient of variation (CV) of each individual hormone data set to the respective assay CV, 2) examining each data set for pulses, and 3) relating changes in hormone levels to the ingestion of a meal. The CV for each individual progesterone data set was greater than the assay CV (CV progesterone, 3.7%) in all subjects (range, 5.58-21.90%). The CV for each individual hCG data set was greater than the assay CV for hCG (CV hCG, 4.3%) in 17 of 19 subjects (range, 3.27-10.95%). Mean (+/- SE) progesterone and hCG peak frequencies were 2.4 +/- 0.3 and 1.7 +/- 0.3/24 h, respectively. When postprandial levels of progesterone were normalized to a percentage of preprandial levels, there were maximum decreases in mean progesterone levels of 15.4 +/- 2.6% and 13.1 +/- 1.9% 1 h after initiation of the lunch and dinner meals, respectively (P less than 0.05). Postprandial hCG levels decreased by 2.3 +/- 1.9% and 0.4 +/- 1.6% during this same time period (P greater than 0.05). These findings suggest that 1) both progesterone and hCG levels fluctuate during a 24-h period in early pregnancy; 2) this variability of both hormones is greater than inherent assay variability and can be resolved into a short term pattern of pulses, suggesting alterations in episodic secretion, metabolic clearance, or volume of distribution of the hormone; and 3) a portion of the variability in the progesterone time set may be due to the ingestion of meals.

Serial study of T-lymphocyte subsets in women during very early pregnancy

The aim of this serial study was to define variations in T-lymphocyte populations during the first weeks of pregnancy. Results obtained with 14 women pregnant after artificial insemination show that the CD4 + population decreased significantly as soon as the fourth week. This decrease was concomitant with the HCG peak and could be compatible with certain immunological mechanisms participating in tolerance to the fetal graft.

Characterization of Human Chorionic Gonadotropin Internalized by Pseudopregnant Rat Ovary*

Peptide hormones may be internalized by target cells in a time- and dose-dependent manner. Since the predominant intracellular form of hCG internalized by cells of the pseudopregnant rat ovary was free, not receptor-bound, hormone, studies were undertaken to characterize subcellular hCG by Sephadex G-100 chromatography, Leydig cell bioassay, and binding to Concanavalin A-Sepharose 4B (Con A-Sepharose) 1, 3, 6, 12, and 24 h after the injection of groups of rats with a single 1.0-/xg dose of hCG (CR119). On Sephadex G-100 chromatography, a major immunoreactive hCG peak eluted slightly before the elution point of highly purified hCG. Smaller immunoreactive hCG peaks, consistent with degraded hCG, were observed and were prominent 6, 12, and 24 h after hormone injection. No free hCG subunits were observed. One hour after the iv hCG injection, the biological to immunological ratio of subcellular hCG was greatest; this progressively decreased at 3 and 6 h. However, no significant biological activity was present ...

Serum concentrations of human chorionic gonadotrophin and its alpha and beta subunits. 1. During normal singleton and twin pregnancies.

Homologous radioimmunoassays have been developed for native hCG and its alpha and beta subunits. Their specificities were assessed by analysis of the inhibition ca and beta subunits. 1. During normal singleton and twin pregnancies.

Large immunologic species of human chorionic gonadotropin in placental extracts.

Gel filtration of extracts of human chorionic tissues cultivated in vitro and of culture media has been performed. Heterogeneous immunoreactive forms of hCG and its subunits in tissue extracts were apparent. A void-volume immunoreactive peak of hCG was identified in extracts of chorionic tissues cultivated for a very short period. The immunoreactive void-volume material, which did not readily convert to the authentic form of hCG either spontaneously in refiltration or in 5 M guanidine, could not be distinguished immunologically from purified hCG and yielded an hCG-like component in trypsinization.On gel filtration of chorionic tissue extracts, radioreceptor activity for hCG utilizing membrance fraction of pseudopregnant rat ovary always demonstrated a single peak in the region of 125I-hCG used as column marker, indicating high receptor activity in the authentic form of hCG and low in the large immunologic species of hCG. Heterogeneity in the molecular size of bicactive hCG was not found with radioreceptor assay.On the other hand, gel filtration profiles of chorionic tissue extracts and of culture media showed that the large immunologic species of hCG is a predominant form of the hormone in the chorionic tissue cultivated for a short period and the authentic form of hCG is a predominant form in the media. These data suggest that immunoreactive “big hCG” synthesized initially in placenta may be converted to the authentic form of hCG by trypsin-like enzyme and that the authentic form of hCG may be readily secreted into the media. These results support the proposal that hCG is also synthesized as prohormone in placenta. However, the biosynthetic process of hCG subunits remains yet to be resolved.

Studies on in vitro synthesis and secretion of human chorionic gonadtropin and its subunits.

Human chorionic tissues were cultivated in vitro in they presence of 3H-proline in order to study the synthesis of the hCG and its subunits by the placenta. After terminating the culture, tissue extracts and media were individually gel-filtrated on Sephadex G-100. The eluted fractions were radioimmunoassayed for hCG, hCGalpha and hCGbeta and were measured for 3H-radioactivity. Label incorporation was determined by immunoprecipitation. Elution profiles of tissue extracts showed the existence of large immunologic forms of hHCG, hCGalpha and hCGbeta emerging near the void volume. The amounts of these large immunologic species in chorionic tissue gradually decreased during the course of cultivation. 3H-proline was almost exclusively incorporated into the large immunologic forms of hCG, hCGalpha and hCGbeta within the chrionic tissue during the 5-hour exposure. A great quantity of hCGalpha was found in the media after the 3-day culture, while the amount of hCGbeta found in the media was minute. After a 15-minute pulse, the 3H-radioactivity peak within the chorionic tissue appeared in the void volume, conicidental with hCG immunoreactivity. During the chase period, there was shift of the 3H-radioactivity peak associated with hCG immunoreactivity from the void volume to the more retarded area. In the media until after the 60-minute chase, no labeled hCG and its subunits appeared. Within the media after 3-hour chase, no labeled hCG peak associated with 3H-radioactivity was more retarded on Sephadex G-100 than that within the tissue extract after the 15-MINUTE pulse. These results suggest that the large immunologic forms of hCG, HCGalpha and hCGbeta are synthesized as the earliest detectable biosynthetic forms and that the may then be converted to small molecule species. In the culture of molar trophoblastic tissues after a 15-minute pulse, considerable amounts of hCG and its subunits accompanied by high 3H-radioactively had already been secreted into the media. These observations suggest that protein synthesis by molar trophoblastic tissue is markedly enhanced as compared with that by normal chorionic tissue and that immunoreactive materials synthesized in molar trophoblastic tissue may be secreted more radily than those synthesized a in normal chorionic tssue.

Influence of early pregnancy on lipid and carbohydrate metabolism in normal females.

In continuation of previous publications (1-4), progesterone, HCG and HPL values in blood from patients in early pregnancy were related to carbohydrate and fat metabolism. Nine patients with an average age of 30 were compared statistically with themselves. Eight of these patients had ovarian insufficiency and were treated with clomiphendihydrogencitrate (Dyneric®), and one had a normal menstrual cycle. After a failure to menstruate and a continually high basal temperature were demonstrated, fasting blood was collected at 8 a. m. every 14 days until the 110th day of pregnancy. Increases and fluctuations of the progesterone and HPL concentrations were comparable to the literature (5, 6). Also the HCG peak between the 60th and 70th day of pregnancy at an average value of 60 IU/ml correlated with previous publications (7). A clear correlation was seen between the increased progesterone and the triglycérides. The free fatty acids were also increased in early pregnancy during the 7th to 16th week. We as well as Fioretti (8) noticed a decrease in blood glucose. The question concerning the influence of progesterone on this parameter remains unanswered. Kalkhoff (9) showed a definite correlation between progesterone and blood insulin without an increase of blood glucose.

Continuous monitoring of plasma FSH, LH, HCG and placenta lactogen during HMG-induced ovulatory cycles and subsequent pregnancies.

ABSTRACT This study gives a description of the pattern of plasma FSH, LH/HCG, and HPL in four patients with sterility problems suffering from ovarian insufficiency. Plasma values were assayed daily during HMG- and HCG-treatment, in the luteal phase and in the first few weeks of subsequent pregnancy by the dioxane and propanol precipitation radioimmunoassays. From the data obtained the following conclusions may be drawn: HMG-treatment induces no or only a slight increase in plasma LH as compared with normal follicular phases. A cumulative effect does not become evident, probably due to the short half-life of 21 minutes and 4 hours respectively. Injection of 10 000 to 15 000 IU HCG causes a marked increase in plasma level above 200 mU/ml and a subsequent depression in 4 to 5 days, corresponding to the long half-life of 5 and 23 hours respectively. During the five days before the rise in endogenous HCG/LH, values are in the same range or somewhat higher than during HMG-treatment and than in normal luteal phase. Between the 10th and 11th day after HCG injection a very sharp rise in endogenous HCG is observed, reaching 10 IU/ml within 15 to 20 days. FSH levels in the treatment period are augmented above the levels observed in normal follicular phases. Though there is no peak around the time of ovulation, a relative high FSH content can be noted. During the luteal phase FSH-values remain elevated and are higher than in normal cycles. Parallel to the rise in HCG, the FSH falls and is found to be very low during early pregnancy. In one patient with severe ovarian hyperstimulation the FSH concentration was different, with high levels in the first few weeks of pregnancy. Measurable HPL production was first detectable between day 28 and 32 after the ovulatory HCG peak. By the 10th week of gestation this hormone showed a constant increase. Possible explanations for the differences between the induced and physiological cycles are discussed.