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

Iles, Ray K., Javid, Mohammed K., Gunn, Lionel K. and Chard, Tim (1999) 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. Clinical Chemistry, 45 . pp. 532-538. ISSN 0009-9147 [Article]

Abstract

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.

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