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. 17beta-estradiol + NAD(+) = estrone + H(+) + NADH 17beta-estradiol + NADP(+) = estrone + H(+) + NADPH NAD(+) + testosterone = androst-4-ene-3,17-dione + H(+) + NADH Steroid biosynthesis; estrogen biosynthesis. Lipid metabolism; fatty acid biosynthesis. Heterotetramer with CBR4; contains two molecules of HSD17B8 and CBR4. Belongs to the short-chain dehydrogenases/reductases (SDR) family.