Intact HCG, free HCG β subunit and HCG β core fragment: longitudinal patterns in urine during early pregnancy

• Published in: Human reproduction (Oxford) Vol. 20; no. 4; pp. 928 - 935
• Main Authors: McChesney, Ruth, Wilcox, Allen J., O'Connor, John F., Weinberg, Clarice R., Baird, Donna D., Schlatterer, John P., McConnaughey, D.Robert, Birken, Steven, Canfield, Robert E.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.04.2005
• Subjects: Adult; Biological and medical sciences; Biomarkers; Chorionic Gonadotropin - urine; Chorionic Gonadotropin, beta Subunit, Human - urine; Female; Gynecology. Andrology. Obstetrics; HCG; Humans; longitudinal patterns; Longitudinal Studies; Medical sciences; Ovulation; Pregnancy; Pregnancy Tests - methods; Pregnancy Tests - standards; Pregnancy Trimester, First - urine; Prospective Studies; Reproducibility of Results; urine; urine; HCG; pregnancy; longitudinal patterns; Urine; Biological fluid; Human chorionic gonadotrophin; Vertebrata; Mammalia; HCG/longitudinal pattems/pregnancy/urine; Early pregnancy; Gonadotropin; Subunit; Fragment; Placental hormone
• ISSN: 0268-1161; 1460-2350
• DOI: 10.1093/humrep/deh702

BACKGROUND: Detecting and monitoring early pregnancy depend on the measurement of HCG. Little is known about how production of various forms of HCG may evolve over the earliest weeks of pregnancy, particularly in naturally conceived pregnancies. METHODS: We describe the daily excretion of three urinary HCG analytes during the first 6 weeks post-conception in 37 naturally conceived pregnancies ending in singleton birth. We assayed daily first morning urine samples for intact HCG, free β subunit and \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({\beta}?\) \end{document}core fragment, plus the combined measurement of these HCG forms. We calculated doubling times for each analyte and the inter- and intra-subject day-to-day variation. RESULTS: Intact HCG and the free β subunit were initially the predominant forms of HCG, with the β core fragment emerging as the predominant form in the fifth week after conception. Intact HCG and the free β subunit showed the most day-to-day variability, and were transiently undetectable even 10 days after detection of pregnancy. The most stable estimate of doubling time was provided by the combined measurement of all these forms. CONCLUSIONS: Although intact HCG is usually regarded as the main analyte for detection and monitoring of early pregnancy, it can fluctuate markedly during early pregnancy. This variability could affect pregnancy test results based on early pregnancy urine, and may distort estimates of doubling time. Assays that combine several forms of HCG may be more reliable.