The invention provides isolated nucleic acids molecules, designated DHDR nucleic acid molecules, which encode novel DHDR-related dehydrogenase molecules. The invention also provides antisense nucleic acid molecules, recombinant expression vectors containing DHDR nucleic acid molecules, host cells into which the expression vectors have been introduced, and nonhuman transgenic animals in which a DHDR gene has been introduced or disrupted. The invention still further provides isolated DHDR proteins, fusion proteins, antigenic peptides and anti-DHDR antibodies. Diagnostic methods utilizing compositions of the invention are also provided.