An interlaboratory study on the use of steroid hormones in examining endocrine disruption

In recent years, there has been an increased use of the measurement of sex steroid hormone levels in the blood of animals exposed to chemicals as an i ndicator of reproductive impairment or an alteration in endocrine function. Although levels of hormones are often compared among animals and laborator ies, there has been no study to examine the between-lab oratory variability in actual steroid measurements. Therefore, we initiated a study with white sucker collected from a site receiving pulp mill effluent, previously docu mented as having reduced steroid levels, to address this issue. Samples of plasma and media from in vitro gonadal incubations were delivered to eight outside laboratories with the ability to measure steroid hormones. These la boratories ran-ed from well-established fish endocrine laboratories to wild life toxicology laboratories, which have recently implemented the methods t o measure steroid hormones. In this study, we have considered both the abso lute measure of steroid content between laboratories as well as the ability to discriminate between reference and exposed populations as important cri teria when evaluating the utility of these measures. Of the eight outside l aboratories conducting the analyses, six detected identical site difference s in circulating levels of testosterone and 17 beta -estradiol to those doc umented by our Burlington laboratory (ON, Canada). However, the absolute va lue of the steroid hormones measured in the plasma varied significantly (pl asma testosterone 0.6-23.1 ng/ml, 17 beta -estradiol 77.6-1782.7 pg/ml) wit h coefficients of variation of 70.4% and 60.3% respectively. Similar result s were demonstrated for the measurement of steroid hormones in media follow ing in vitro gonadal incubation. Although there was a fair amount of variab ility in the absolute measure of steroid hormone levels, we would predict a far greater coherence of interlaboratory results through the sharing of re agents and the use of a common methodology between laboratories. These resu lts are very promising, providing evidence for the inclusion of steroid hor mones in monitoring endocrine disruption in wildlife species.