Journal of Andrology Proceedings of the Fifth International Conference on the Epididymis
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Rosenfield, R. L.
Right arrow Articles by Helke, J.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Rosenfield, R. L.
Right arrow Articles by Helke, J.

Journal of Andrology, Vol 13, Issue 1 1-10, Copyright © 1992 by The American Society of Andrology

JOURNAL ARTICLE

Is an immunoassay available for the measurement of bioactive LH in serum?

R. L. Rosenfield and J. Helke
Department of Pediatrics, University of Chicago, Pritzker School of Medicine, Wyler Children's Hospital, Illinois 60637-1470.

An in vitro bioassay for luteinizing hormone (LH) is in our opinion the "gold standard" bioassay. The rodent interstitial cell testosterone assay (RICT) is specific for bioactive LH and very sensitive, accurate, and reproducible. Diverse LH standards consistently display parallel dose-response characteristics. Sera also manifest parallel dose-response characteristics throughout reproductive life, with the exception of basal samples from prepubertal children. This indicates that all known hormones with LH bioactivity have a similar bioactive site. The in vivo bioassays for LH used for calibration of World Health Organization standards are more cumbersome and less precise and accurate than the in vitro bioassay. The ovarian ascorbic acid depletion assay corresponds better than the seminal vesicle weight assay with in vitro bioassay. Variation in the ratio of bioactive to immunoreactive LH (B/I) principally reflects variation in LH immunoassay dose-response characteristics, rather than a change in the bioactive moiety of LH. The varying B/I ratio is due to molecular heterogeneity at multiple levels. Different LH standards contain different proportions of nonbioactive but immunoreactive material. The immunoreactive LH isoforms in serum contain different proportions of bioactive material and the isoform distribution differs with reproductive status. Furthermore, the antibodies comprising the various immunoassay systems detect heterogeneous epitopes on LH, which are not necessarily bioactive. B/I ratio disparities indicate lack of specificity of immunoassays for bioactive LH. Polyclonal antibody-based radioimmunoassay requires the use of purified reagents, including a bioactive tracer, in order to achieve high specificity for bioactive LH. The new generation of monoclonal antibody-based immunometric assays yields results that are lower than, but correlate with, LH measured by the in vitro bioassay. The purest of standards, even a recombinant standard, yields results that differ up to 50% or more from one immunoassay to another. Serum LH levels also differ up to two-fold among assays. The immunometric assays have the advantage of being more sensitive and more specific for low levels of LH in serum than radioimmunoassays, but B/I ratio discrepancies remain great. An immunoassay specific for the bioactive "docking site" of human LH isoforms is still needed.




HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1992 by The American Society of Andrology.