In vitro bioassays for androgens and their diagnostic applications.

Androgen levels are measured in today's clinical practice almost exclusively by immunoassays. The androgen that is most frequently determined is testosterone (T), but sometimes also the levels of other testicular, ovarian and adrenal androgens such as 5alpha-dihydrotestosterone, androstenedione, dehydroepiandrosterone and its sulphate may be determined. In many instances, especially when androgen levels are low (as in women and children), the quality of the immunomeasurements is insufficient and the correlation between hormone levels and clinical symptoms is poor. One alternative to improve the clinical relevance of androgen measurements is provided by the recently developed in vitro bioassays of total androgen bioactivity in serum. These assays are not yet ready for routine laboratory diagnostics, but they provide a useful tool for clinical research in disturbances of androgen production. Another application of these assays is the screening for androgenic and antiandrogenic activity in chemical compounds, environmental samples and when suspecting androgen abuse. The purpose of this article is to introduce the current problems of androgen measurement by immunoassays, to describe the novel in vitro bioassay techniques and to review the current information on their application in clinical research.