A major surgical operation, usually coupled with the appropriate hormone treatment (see HORMONES), to change a person's anatomical sex. The operation may be requested by transsexual individuals or those whose sexual organs are neither totally female nor male. Male-to-female sex change is the more common. Such operations should not be performed without rigorous physical and psychological assessment of the individual, and should be accompanied by extensive counselling. Some subjects make a satisfactory adjustment to the change of anatomical sex, while others may suffer serious psychological problems. Hormone therapy may need to be continued for life. See also GENDER IDENTITY DISORDERS.