Previously known as testicular feminisation, this genetically acquired condition means that, despite having male chromosomes, the person does not respond to testosterone (the male sex hormone) properly and male sexual development is anomalous. Thus, depending on the degree of insensitivity, the penis may not form or is underdeveloped. The child's external genitals may appear fully female, or between male and female, but they do not have a uterus or ovaries and have fully or partially undescended testicles. The dilemma for parents, clinicians and ultimately the child is what sex is best assigned and what measures are required to aid this.