17Beta-HSD4 (17Beta-hydroxysteroid dehydrogenase type 4) is also known as peroxisomal multifunctional enzyme/protein 2 (MFE-2/MFP-2), D-bifunctional enzyme or 17-Beta Estradiol dehydrogenase type IV. It belongs to the 17Beta-HSD family of proteins that regulate the availability of steroids within various tissues throughout the body. 17Beta-HSD4 inactivates Estradiol through its oxidative activity but it is primarily involved in peroxisomal fatty acid and cholesterol Beta-oxidation. It has a multi-domain structure: the dehydrogenase domain is fused to a hydratase and a lipid transfer domain. 17Beta-HSD4 is a target protein of chromeceptin and it is essential for the downstream activation of Stat6. 17Beta-HSD4-deficient patients exhibit Zellweger-like syndrome and die within the first year of life. They display neuronal migration defects, facial dysmorphisms, severe hypotonia and convulsions in the neonatal period.