Influence of estrogen replacement therapies such as premarin for the measurement of estradiol

: To investigate problems associated with the measurement of estradiol 17 beta(E2) in hormone replacement therapy(HRT), five commercial immunoassay methods(Coat-A-Count E2 as the conventional method; Immulyze E2, Immuno 1 E2, Vitros E2, and HRT-E2 as the comparative methods) were used to assay E2 concentrations. Samples were obtained from 21 women who had been receiving HRT, 99 nonmedicated women, and 10 healthy men volunteers. No significant difference between the Coat-A-Count E2 and the comparative method was observed in the nonmedicated women. However, we found that the serum E2 concentration from patients taking Premarin showed a large discrepancy between the Coat-A-Count E2 method, which showed considerably higher values, and the other four methods. The reason for our conflicting results from patients with HRT was probably because the Coat-A-Count E2 detected circulating estrogen conjugates. The experimental addition of Premarin for the in vitro cross-reactivity was done. The cross-reactivity was low because a similar E2 steroid exists independently. However, the E2 serum value of the ten male volunteers after taking Premarin was elevated. The reason for this result was due to the high cross-reactivity between anti E2 polyclonal antibody and the various metabolic products of Premarin. In conclusion, the influence of Premarin should be taken into consideration when measuring estradiol concentration to monitor HRT.