Enables 3-oxo-5-alpha-steroid 4-dehydrogenase activity; NADPH binding activity; and amide binding activity. Involved in several processes, including animal organ development; cellular hormone metabolic process; and cellular response to organic cyclic compound. Located in several cellular components, including cell body fiber; neuronal cell body; and perinuclear region of cytoplasm. Used to study prostate cancer. Biomarker of hyperprolactinemia; hypothyroidism; obesity; prostate cancer; and type 2 diabetes mellitus. Human ortholog(s) of this gene implicated in prostate cancer and prostatic hypertrophy. Orthologous to human SRD5A1 (steroid 5 alpha-reductase 1). [provided by Alliance of Genome Resources, Apr 2022]