NAD-dependent 17-beta-hydroxysteroid dehydrogenase with highest activity towards estradiol. Has very low activity towards testosterone. The heterotetramer with CBR4 has NADH-dependent 3-ketoacyl-acyl carrier protein reductase activity, and thereby plays a role in mitochondrial fatty acid biosynthesis. Within the heterotetramer, HSD17B8 binds NADH; CBR4 binds NADPD.
Subcellular locations: Mitochondrion matrix