Anti-steroid-5-alpha-reductase, alpha polypeptide 1 (3-oxo-5 alpha-steroid delta 4-dehydrogenase alpha 1) antibodies are used in antigen-specific immunodetection in biological samples. The target steroid-5-alpha-reductase, alpha polypeptide 1 (3-oxo-5 alpha-steroid delta 4-dehydrogenase alpha 1) is a known alias name of the protein steroid 5 alpha-reductase 1, encoded by the SRD5A1 gene in humans. This 259-amino acid residue protein is known to be involved in bone development and cell differentiation, among other biological processes. It is localized to the ER of the cell. It is reported to be widely expressed in many tissue types. Other synonyms for steroid-5-alpha-reductase, alpha polypeptide 1 (3-oxo-5 alpha-steroid delta 4-dehydrogenase alpha 1) include S5AR 1, 3-oxo-5-alpha-steroid 4-dehydrogenase 1, and SR type 1.