While this is consistent with our finding for total testosterone and HER2-enriched breast cancer risk (OR = 0.98, 95% CI:0.81, 1.18), there was an indication that bioavailable testosterone reduced risk of HER2-enriched breast cancer (OR = 0.86, 95% CI:0.69, 1.07) although this was imprecisely estimated. This evidence concerns the gene ERBB2 and breast cancer.