A state of indeterminate sexuality of an individual, and may present in many different forms. A characteristic is that only one type of gonad – testis or ovary – is present; in a HERMAPHRODITE, both types are present. Intersexuality may be due to a fault in the genetic mechanism of sex determination as early as conception; or to later errors in sexual differentiation of the embryo and fetus, or after birth. Some cases may result from abnormal metabolism of the sex hormones, or may be drug-induced (for example, women given androgens [see ANDROGEN] or PROGESTERONE for repeated miscarriages may give birth to girls with some genital VIRILISATION). Abnormalities of the sex chromosomes may be associated with delayed (or failure of) sexual development, so that the individual shows some of the characteristics (often underdeveloped) of both sexes. Some of the more common presentations of the condition include HYPOGONADISM, CRYPTORCHIDISM, and primary AMENORRHOEA.

Intersexuality inevitably leads to considerable family anxiety as the child grows up. It is therefore important to agree a decision as to the child's sex – or at least, the sex that he or she is to be brought up as. Surgical or hormonal means can be offered at specialist centres, when appropriate, to develop the attributes of that sex and diminish those of the other, together with psychological counselling. Fully informed patient consent is a major issue to be considered.