Highly sensitive radioimmunoassay for chorionic gonadotropin in human urine

Human chorionic gonadotropin and maternal recognition of pregnancy

The corpus luteum of the ovulatory cycle is essential for establishing and maintaining the first seven weeks of human pregnancy. Progesterone, given parenterally, appears to be a satisfactory substitute for the corpus luteum, known to be the source of this steroid hormone during this period. Moreover, hCG appears to be essential for sustained secretion of progesterone by the corpus luteum, particularly during the first three weeks after fertilization. In primates at least, neutralization of the biological effects of CG during this critical period results in a reduction of blood progesterone levels and the interruption of pregnancy. Although alternative sources of hCG exist, and the physiological relevance of these sources requires further study, hCG appears to be essential component in the maternal recognition of pregnancy.

Pathophysiological importance of various molecular forms of human choriogonadotropin

Human chorionic gonadotropin (hCG), its subunits and fragments are widely used for diagnostic purposes. In addition to the diagnosis of pregnancy and pregnancy related disorders, hCG determinations are used for diagnosis of trophoblastic and recently also nontrophoblastic tumors. The use for diagnosis of nontrophoblastic tumors requires highly specific and ultrasensitive assays. With these, it is possible to measure the concentrations of both hCG, the free beta-subunits and the so called beta-core fragment in healthy subjects. Therefore it is important to establish reference values for these and also to be aware of the influence of physiological factors on the serum and urine concentrations. Improved standardization of the assay methods is also essential for these novel applications of hCG determinations to become useful.

Gestational trophoblastic disease: what have we learned in the past decade?

Hydatidiform moles can be classified into two distinct entities: complete and partial. Complete moles are androgenetically derived, are characterized by a predominance of the 46,XX karyotype, and are associated with a significantly higher incidence of malignant sequelae than are partial moles. A subset of complete moles resulting from dispermy are heterozygous (46,XY) and appear to be associated with the greatest risk of malignancy. Free subunits of human chorionic gonadotropin, beta core fragments, and acidic variants of human chorionic gonadotropin can now be readily measured by radioimmunoassays, fluoroimmunoassays, or isoelectric focusing techniques. Determination of these markers can be of value not only in monitoring response to therapy, but also as prognostic indicators. A subgroup of patients, traditionally classified as "high risk" or poor prognosis, who show poor responses to conventional combination chemotherapy have recently been designated as "ultra-high-risk" patients. They require more complex chemotherapy and possibly surgery and radiotherapy to achieve remission. The development of chemotherapy over the past decade, including the introduction of etoposide and cisplatin into current protocols and the treatment of patients with advanced gestational trophoblastic disease, are considered in this review.

A highly sensitive and specific sandwich enzyme immunoassay for detection of human chorionic gonadotropin in trophoblastic disease

A highly sensitive and specific two-site enzyme immunoassay (EIA) kit for human chorionic gonadotropin (hCG) has been examined and applied to the detection of hormones in the serum of normal individuals and patients with trophoblastic disease. This EIA uses a solid phase coupled antibody to the unique COOH terminal peptide region of the hCG beta-subunit (beta-CTP) and an enzyme conjugated monoclonal antibody to the hCG beta-subunit. The overnight 2 step assay measured as little as 0.2 mIU/ml serum without hLH interference and a rapid one step assay was newly developed in our laboratory. Assays of serum from normal men and nonpregnant women of reproductive age indicated that most individuals did not have detectable serum levels of hCG immunoreactivity, although a minority had minute amounts. In contrast, women with non-functional ovaries had detectable levels of hCG immunoreactivity with a mean value of 0.86 mIU/ml serum. The extremely high sensitivity and specificity of the EIA in detecting hCG provides substantial advantages for the detection of early pregnancy and for monitoring trophoblastic tumors.

Human chorionic gonadotropin, follicle-stimulating hormone, and luteinizing hormone in patients with epithelial ovarian carcinoma

Plasma levels of human chorionic gonadotropin (hCG), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) were studied in patients with epithelial ovarian carcinoma prior to and during chemotherapy. Blood samples were drawn for radioimmunoassay at monthly intervals. Plasma concentrations were compared to those of three different control groups: healthy post-menopausal women (PM), fertile women in the follicular phase of the menstrual cycle (FPh), and postmenopausal women with nongynecologic disseminated malignant disease (DMD). The hCG level was elevated in women with great tumor burden, such as large tumor volume, FIGO stage IV, and histologic type V. LH and FSH levels showed the reverse pattern. hCG concentration decreased during chemotherapy, whereas LH increased. Initial plasma concentrations were not found to have prognostic importance. We discuss the possibility that hCG is produced by the tumor, which stimulates steroid hormone production by the stroma, which, in turn, exerts negative feedback on FSH production by the pituitary.

Beta-subunit of baboon chorionic gonadotropin. Continuous flow Fmoc-polyamide synthesis of the C-terminal 37-peptide

The synthesis of a 37-peptide fragment derived from the carboxyl terminal of the beta-subunit of baboon chorionic gonadotropin has been accomplished by the continuous flow Fmoc-polyamide solid phase method. The use of N alpha-fluorenylmethoxy-carbonyl-glutamine with its sidechain protected by the 4,4'-dimethoxybenzhydryl group enabled successful incorporation of this residue onto a hydroxymethyl linkage agent without apparent side reaction.

Comparison of the analytical characteristics and clinical usefulness in tumour monitoring of fifteen hCG(-beta) immunoassay kits

Fifteen immunoassay kits for serum hCG(-beta) measurements have been compared for their analytical characteristics and clinical usefulness in tumour monitoring. Three out of 13 radioimmunoassays and two sandwich hCG immunoassays represent the 'one-component' techniques for intact hCG detection since they are based on antiserum raised against intact hCG. Within this group, method-comparison slopes ranged between 0 X 149 and 0 X 374. The remaining 10 radioimmunoassays all apply antiserum against hCG-beta and are designated 'two (or more)-component' assays since they detect both intact hCG and the free beta-subunit ('total hCG'). For this reason these assays are of potential value for tumour monitoring. Additional criteria for this are: (1) the expression of assay results in terms of 1st IRP-hCG instead of the unstructured use of the 2nd IS or the 1st IRP-hCG-beta; (2) documentation of cross-reactivities especially for the free beta-subunits of hCG and hLH which are almost completely lacking; (3) establishment of the minimum detectable dose in the presence of normo-to-hypergonadotrophic hLH levels in serum (the 'clinical sensitivity') to allow the follow-up of tumour regression especially in the low-dose region. Method-comparison analysis for these assays revealed regression slopes between 0 X 001 and 0 X 873.

Efficient extraction and sensitive radioimmunoassay for hCG in human urine

A single-step procedure for extracting and concentrating hCG in 24-h urine samples was developed. The procedure involves adsorption chromatography with Vitachange. The hCG recovery was more than 90% compared with about 51% for the standard kaolin-acetone method. Nonspecific urinary protein concentration of extracts was also reduced. Thus, this method for concentration of urinary hCG with subsequent radioimmunoassay (RIA) using an antiserum against the unique carboxylterminal peptide of hCG beta subunit provides a sensitive and specific method for detecting hCG in urine.

Secretion of human chorionic gonadotropin and alpha-fetoprotein by an ovarian germ cell tumor of apparent yolk sac origin

alpha-Fetoprotein (alpha FP) and four placental proteins, human chorionic gonadotropin (hCG), human placental lactogen (hpL), pregnancy specific beta 1-glycoprotein (SP1), and placental protein 5 (PP5), were measured in a 17-year-old patient with endodermal sinus tumor of the ovary. The circulating levels of alpha FP were consistently high (more than 14 mg/ml), and alpha FP was localized in tissue sections using immunohistochemical techniques. None of the four placental proteins was detectable in serum samples, but hCG was detected in urinary concentrates in an episodic manner. This ectopic hCG resembled placental hCG in its physicochemical and immunological characteristics. Unlike alpha FP, hCG was not detected in the tumor by immunohistochemical methods. This study indicates that the neoplasm elaborated both hCG and alpha FP. Whether pure endodermal sinus tumor of the ovary is capable of secreting hCG cannot be answered by this study because of limited histologic sampling. The likelihood that this represents a mixed germ cell tumor in which only the endodermal sinus tumor element was sampled remains a possibility. This study also indicates that the 24-hr urinary concentrate is far more sensitive than serum samples for hCG detection.

New horizons in hCG detection

The advent of high technology in the field of hCG measurement has created a greater requirement for high expertise in the analysis and evaluation of hCG levels, particularly low-positive levels, and for the concomitant clinical management of the patient. This implies an imperative to treat trophoblastic disease patients in trophoblast disease referral centers.

Human chorionic gonadotropin and alpha chain of glycoprotein hormones in patients with inflammatory bowel disease

In twenty patients with Crohn's disease and ten patients with ulcerative colitis serum levels of human chorionic gonadotropin and the common alpha-subunit of glycoprotein hormones were determined by radioimmunoassay. In contrast to published data, all serum samples except one revealed levels within the normal range of 148 controls (human chorionic gonadotropin levels up to 3.9 IU/l, alpha-subunit up to 3.8 micrograms/l). Neither the serum levels of human chorionic gonadotropin nor of the alpha-subunit differed significantly between patients with Crohn's disease (median/maximum: 0.9/4.4 IU/l; 0.7/3.6 micrograms/l) and ulcerative colitis (1.0/3.4 IU/l; 0.8/2.2 micrograms/l). Furthermore, the serum levels studied in patients with active (0.9/3.0 IU/l; 0.7/3.5 micrograms/l) and inactive (0.9/4.4 IU/l; 0.8/3.6 micrograms/l) Crohn's disease and in patients with active (1.1/3.4 IU/l; 0.9/2.2 micrograms/l) and inactive (0.9/2.9 IU/l; 0.8/1.3 micrograms/l) ulcerative colitis were not significantly different. There was no relationship of the duration of the disease or a bowel resection to the serum levels of human chorionic gonadotropin or the alpha-subunit. It is concluded that both parameters are not useful as markers in patients with Crohn's disease or ulcerative colitis. The normal serum levels found in patients with inflammatory bowel diseases indicate human chorionic gonadotropin as a highly specific marker for malignant diseases.

Human chorionic gonadotropin immunoreactivity in serum of patients with malignant neoplasms

The beta-human chorionic gonadotropin (HCG) radioimmunoassay was used to determine the presence of HCG immunoreactivity in serum of patients (n = 71) with diagnosis of cancer. Of patients with active neoplasia, 60.5% showed HCG immunoactivity above controls (greater than 5 mIU/ml). An apparent degree of correlation was observed with tumor activity in that a case with widespread metastases due to a colonic carcinoma exhibited the highest HCG levels while, in one patient, the level of HCG decreased progressively according to therapeutic response. A high frequency of immunoactive HCG was found in patients with carcinomas of the cervix, breast, gonad, and digestive system and in patients with melanoma. Trophoblastic cells were not evident in the tumors biopsied. Immunologic similarity of HCG secreted by tumors and that contained in serum of pregnant women, of patients with hydatidiform mole, and of males injected with exogenous HCG was shown by parallel inhibition curves in the radioimmunoassay. The positivity of HCG was predominant in cases of cervix carcinoma.

Characterization of a carboxyterminal peptide fragment of the human choriogonadotropin beta-subunit excreted in the urine of a woman with choriocarcinoma

We have observed low-molecular weight carboxyterminal fragments of the human choriogonadotropin (hCG) beta-subunit in the urines of several women with choriocarcinoma, and we have characterized one fragment in detail. Its apparent molecular weight by gel chromatography on Sephadex G-100 was 14,200. The fragment was not adsorbed to concanavalin A-Sepharose, indicating that it lacked the asparagine-linked carbohydrate groups of intact hCG beta. It was active in radioimmunoassays (RIA) using antisera either to the hCG beta carboxyterminal peptide (CTP) or to the desialylated hCG beta CTP (hCG beta as-CTP), indicating the presence of not only the hCG beta carboxyterminus but also desialylated O-serine-linked carbohydrate side chains on the fragment. It lacked luteinizing hormone/choriogonadotropin radioreceptor activity and hCG beta conformational immunoreactivity (SB6 RIA). On Sephadex G-100 gel chromatography, the elution profiles of this fragment and the hCG beta as-CTP(115-145) prepared by trypsin digestion of as-hCG were essentially indistinguishable (apparent molecular weights 14,200 and 14,000, respectively). The immunological characteristics of the fragment in both hCG beta CTP and hCG beta as-CTP RIA were indistinguishable from those of the hCG beta as-CTP(115-145) glycopeptide. Carboxyterminal fragments of hCG beta were evident in urine specimens obtained from 10 of 11 patients with choriocarcinoma but not in those obtained from normal subjects who were given an intravenous infusion of highly purified hCG. Of six pregnant women, only the one at term excreted carboxyterminal fragments of hCG beta and then only in trace amounts. We conclude that hCG beta carboxyterminal fragments, including one that is indistinguishable from the tryptic glycopeptide hCG beta as-CTP(115-145), can occur naturally in the urine of patients with choriocarcinoma.

Human chorionic gonadotropin detected in urinary concentrates from patients with malignant tumors of the testis, prostate, bladder, ureter and kidney

Human chorionic gonadotropin levels in concentrated 24-hour urine and serum were determined by a specific radioimmunoassay of beta-human chorionic gonadotropin in 47 patients with genitourinary carcinoma. Elevated human chorionic gonadotropin levels in urine were observed in 6 of 8 patients with active testicular tumor, 3 of 14 with prostatic cancer, 2 of 10 with bladder cancer, 1 of 2 with ureteral or renal pelvic tumors and 2 of 6 with renal cancer. Of the 14 patients with positive urinary human chorionic gonadotropin 4 had undetectable human chorionic gonadotropin levels in the serum. The tumors of all 8 patients with nontesticular cancer who had increased urinary human chorionic gonadotropin levels were in an advanced clinical stage or of poor histological differentiation. Our results suggest that some nontrophoblastic carcinomas of the genitourinary system are capable of ectopic production of human chorionic gonadotropin, particularly if the malignancy is advanced or poorly differentiated. The radioimmunoassay of beta-human chorionic gonadotropin in concentrated 24-hour urine specimens enhances the sensitivity of detection of ectopic human chorionic gonadotropin production.

Improved monitoring of gestational trophoblastic neoplasia using a highly sensitive assay for urinary human chorionic gonadotropin

A radioimmunoassay for urinary human chorionic gonadotropin (hCG) which used antiserum to the hCG beta carboxy-terminal peptide was employed to detect hCG production in women with gestational trophoblastic disease. The urinary hCG assay was considerably more effective in detecting increased hCG production, and, hence, persistent tumor burden, than the commonly used serum hCG beta subunit radioimmunoassay. In two women treated for choriocarcinoma, urinary hCG levels remained distinctly elevated for 2 to 6 weeks, even though the serum hCG level was undetectable; in both cases, the urinary hCG radioimmunoassay reliably predicted the eventual reappearance of hCG in the serum. In six women whose disease remitted, the urinary hCG level declined to the normal range during chemotherapy, and remained there afterward. In eight patients who had been in remission for periods of from 1 to 14 years, urinary hCG levels were in the normal range. We conclude that this highly sensitive and reliable method for the detection of hCG production improves the ability to diagnose persistent trophoblastic disease.

Thyroid function in gestational trophoblastic neoplasia: evidence that the thyrotropic activity of chorionic gonadotropin mediates the thyrotoxicosis of choriocarcinoma

An investigation was made of thyroid function in 20 patients with gestational trophoblastic neoplasia. Two patients were judged to be overtly thyrotoxic on the basis of the symptoms and physical findings; both patients had widely metastatic choriocarcinoma, markedly increased serum T4 levels (21.4 and 27.7 micrograms/100 ml), and extremely high levels of serum human chorionic gonadotropin (hCG) (3,220 and 6,720 IU/ml) relative to those of normal gestation(< 100 IU/ml). Three other patients had moderately increased serum T4 levels (13 to 17.1 micrograms/100 ml), moderately increased serum hCG levels (110 to 310 IU/ml), and findings on clinical examination which suggested euthyroidism. Using the mouse thyroid bioassay, we found that the biologic characteristics of the thyroid-stimulating factor were those of purified hCG, and that the levels of thyroid-stimulating activity in both serum and urine correlated closely with the levels of hCG. These results provide evidence that the thyroid-stimulating activity intrinsic to the hCG molecule plays the central pathophysiologic role in choriocarcinoma-associated thyrotoxicosis.

Effect of hCGbeta-tt immunization on ovarian morphology in hamster implanted with human choriocarcinoma

Histological analysis of ovaries from hamsters immunized with hCGbeta-tt and implanted with human choriocarcinoma has shown that the gonadotropic activity of hCG was neutralized for 5 days of tumor growth. In control immunized hamsters, hCG secreted from the tumor induced the formation of large, cystic follicles, thecal luteinization and an increase in ovarian mass from Days 1-10 of tumor growth. In contrast, ovarian morphology in hCGbeta-tt immunized hamsters on Days 1-5 of tumor growth resembled that of non-tumor bearing hamsters. Normal follicular growth and corpora lutea formation were observed despite the secretion of hCG by the tumor. Gonadotropic stimulation, as indicated by the presence of cystic follicles, was not evident until Day 10 of tumor growth in hamsters immunized with hCGbeta-tt. hCGbeta-tt immunization did not affect ovarian structure or the normal estrus cycle in hamsters without tumors. These results indicate that the biological activity of hCG in vivo can be inhibited by active immunization with hCGbeta-tt.