Human HSD17B1 induces estradiol production from estrone in vivo. Increased conversion of E1 to E2 was observed in HSD17B1TG mice in all extra-gonadal tissues studied, as compared with wild-type littermate tissues. E1 = estrone, E2 = estradiol, white bars represent wild-type mice, black bars represent HSD17B1TG mice, *P < 0.05, ***P < 0.001.