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Cross-Reaction with Luteinizing Hormone ß-Core Is Responsible for the Age-dependent Increase of Immunoreactive ß-Core Fragment of Human Chorionic Gonadotropin in Women with Nonmalignant Conditions

^a Author for correspondence. Fax 44 0171-600-1439; e-mail R.K.Iles{at}mds qmw.ac.uk.

Background: The ß-core fragment of human chorionic gonadotropin (hCGßcf), also termed "ß-core" and urinary gonadotropin peptide (UGP), has been reported to be present in the urine of healthy women and to increase in concentration after menopause. This could reflect cross-reaction with the equivalent metabolite of luteinizing hormone (LH), the ß-LH-core.

Methods: We measured immunoreactive LH, hCG, free -subunit, and free ß-subunit hCG (hCGß), as well as ß-core, using the S504 RIA and Triton UGP enzyme immunoassay in 274 urine samples from women with nonmalignant gynecological conditions. The molar cross-reaction of each assay with purified ß-LH-core was determined.

Results: Cross-reaction with ß-LH-core was 100% in the LH and the S504 ß-core assay, 5% in the Triton UGP assay, and <0.1% in the hCG, free -subunit, and free hCGß assays. Median urine concentrations of all analytes showed an age-dependent increase. LH and free -subunit concentrations were ~10³ pmol/mol creatinine; hCG and S504 ß-core were ~10² pmol/mol creatinine; free hCGß and Triton UGP ß-core were in the tens of pmol/mol creatinine. The S504 ß-core concentrations were 10% of those of LH. S504 ß-core was strongly correlated with LH, but not with hCG or with free hCGß (LH, r² = 0.45; hCG, r² = 0.26; free hCGß, r² = 0.03). The concentrations of ß-core detected by the Triton UGP assay, which has a 5% cross-reaction with ß-LH-core, were 2% of LH and 5% of the S504 ß-core concentrations. Triton UGP values correlated strongly with LH concentrations, but less well with S504 ß-core, intact hCG, and free hCGß (LH, r² = 0.44; S504 ß-core, r² = 0.33; hCG, r² = 0.32; free hCGß, r² = 0.19).

Conclusions: Immunoreactive ß-core in women free of malignancies reflects cross-reaction with concentrations of the metabolite of LH, ß-LH-core, within the health-related reference interval.© 1999 American Association for Clinical Chemistry

The following articles in journals at HighWire Press have cited this article:

				P. T.A. Borrelli, S. A. Butler, S. M. Docherty, E. M. Staite, A. L. Borrelli, and R. K. Iles Human Chorionic Gonadotropin Isoforms in the Diagnosis of Ectopic Pregnancy Clin. Chem., December 1, 2003; 49(12): 2045 - 2049. [Abstract] [Full Text] [PDF]

				J. F. O'Connor, G. Kovalevskaya, S. Birken, and R. K. Iles Interference of Luteinizing Hormone {beta}-Core Fragment in Urinary Gonadotropin Assays Dr. Iles responds: Clin. Chem., December 1, 1999; 45(12): 2290 - 2292. [Full Text] [PDF]