Incidence and implications of altered semen quality on family planning.

Alterations in the expression of the human genome, or interference with its products, can be induced in the male reproductive system by chemicals mimicking or antagonizing naturally occurring hormones. Opportunities exist for disruption at the hypothalamus, pituitary and testis levels. Recent concerns generated by the increased incidence of testicular cancer, congenital anomalies of the male genitalia and possible alterations in human semen quality have been linked to the environment.