We’re muddying the waters by talking about intersex and similar conditions, but I’ll try and expand a little.

Congenital Adrenal Hyperplasia (CAH), is the most common cause of intersex, resulting in a virilised female due to overproduction of androgens by the foetal adrenal glands. It is commonly caused by a deficiency in 21-hydroxylase, one of the enzymes needed to create the steroid hormones aldosterone and cortisol. When the body cannot make aldosterone and cortisol, the excess precursors are channelled into making testosterone.

Turner’s Syndrome (XO women) results in women without normal ovaries and who need exogenous progesterone and oestrogen to develop normal secondary sexual characteristics. Although they cannot conceive a genetic child of their own, they may be able to carry a pregnancy (created with a donor ovum) to term.

5-alpha reductase deficiency is an enzyme deficiency which means that testosterone isn’t properly converted to dihydrotestosterone, a more available form of the hormone. Because of this male babies are born with feminised external genitalia, but male internal genitalia. If the condition is not recognised, or left uncorrected (as often happens in the developing world) during puberty the amount of testosterone producd by the testes is so great that some of it is able to overcome the block, and considerable virilisation occurs. In this case the male habitus at puberty is associated with gender conversion, so the formerly female child will often self-identify as male. HOWEVER, in the west, if this disorder is recognised early, the testes will be removed prior to puberty (because of the risk of cancer if they are left abdominally) and the child will continue to be raised, and usually identify, as female.

Androgen Insensitivity (formerly known as Testicular Feminisation Syndrome) is the condition normally associated with XY women. In this case the male foetus produces lots of androgens, but the cells do not have the correct receptors, and so the androgen has not effect. These individuals are born with externally feminised genitalia, and unlike with 5 alpha reductase deficiency, this will never spontaneously correct. If testes are present in the abdomen, they are removed, and the child is given female hormones at puberty. These individuals will almost always have a female habitus and gender identity.

True hermaphroditism (possesing both ovaries and testes) is incredibly rare.