A condition in which the testicles cease to produce sperm and hormones or do so in only limited amounts. The testicles are also usually reduced in size. This condition can occur after orchitis, external injuries, torsion of the testicle and undescended testicles. The testicles of some individuals have a predisposition to atrophy, for example in KlinefeIter’s syndrome and in testicular feminization. Atrophy of the testicle frequently leads to infertility.