The androgen receptor (AR) is a nuclear receptor that functions as a transcription factor and regulates the development and growth of the prostate. The AR, when bound by a ligand, complexes with DNA at androgen response elements in the promoter region of target genes. The transcriptional regulatory effects of the AR include pathways involved in cell growth and proliferation, cell cycle progression, protein synthesis, and cell death. The AR is the primary target for endocrine therapy of prostate cancer (PCa) and inhibition of AR signaling has significant benefits for patients with PCa.