Apolipoprotein D(Apo-D) is a protein that in humans, encoded by the APOD gene. Being a member of the alpha (2 mu)-microglobulin superfamily of carrier proteins, Apo-D is also known as lipocalin.The gene has been localized to the p14.2----qter region of human chromosome 3. It is a glycoprotein of estimated molecular weight 33,000 Da. The Apo-D encoded a protein of 169 amino acid residue.It has been detected in human liver, intestine, pancreas, kidney, placenta, adrenal, spleen, and fetal brain tissue. For its features, Apo-D has been a biomarker of androgen insensitivity syndrome (AIS).