Figure 5 shows the dose responses of the antagonistic activity via hAR for the 16 compounds and HF, a known AR antagonist. The order of relative potencies for AR antagonistic activity was 4′-HO-BDE-17 > BDE-100 > 4-HO-BDE-42, BDE-47 > BDE-85 > 4′-HO-BDE-49 > BDE-28 > 4′-MeO-BDE-17, BDE-99 > 4′-MeO-BDE-49, 4-MeO-BDE-42, 4-MeO-BDE-90. From a comparison of RIC20 values, the anti-androgenic activities of 4′-HO-BDE-17 and BDE-100 were about 5- and 10-fold lower than that of HF (1.8 × 10−8 M), respectively (Table 1). Here, AR is linked to hydrops fetalis.