Clinical and molecular aspects of androgen receptor defects.

The androgen receptor (AR) is a ligand-dependent transcription factor involved in various biological processes such as sex differentiation, sexual maturation and spermatogenesis. Disorders of AR function cause a wide spectrum of androgen insensitivity syndromes. The phenotypes vary from women with female external genitalia through patients with genital ambiguity to men with normal male genitalia but infertile. The CAG repeat in exon A is important for transactivation function of the AR and consequently for many androgen-dependent processes. Expansion of this repeat is the cause of the X-linked spinal and bulbar muscular atrophy (SBMA, Kennedy's disease). Mutations of the AR gene occur commonly in prostate cancers and are significant for prognosis of the disease.