Anti-follistatin like 5 antibodies are used in the immunodetection of the protein encoded by the FSTL5 gene. In humans, the canonical protein has a reported length of 847 amino acid residues and a mass of 95.8 kDa. It is known to be a secreted protein. Alternative splicing is reported to yield 3 different isoforms for this protein. The follistatin like 5 protein is involved with cell differentiation, among other functions. Post-translational modifications have been described, including glycosylation. Other names for this target antigen include follistatin-related protein 5 and follistatin-like protein 5.