• Testosterone formation is a multi-step  process  that requires the functioning of different enzymes. Dysfunction of these enzymes can result in its inadequate  production and  results in the formation of  46, XY intersex.

• In some cases of 46, XY intersex, normal internal testes may be present  that ensures adequate  testosterone production. However deficiency in the  enzyme 5-alpha-reductase  impairs the conversion of  testosterone to dihydrotestosterone  a step necessary for proper maleness to manifest.

• Malformation syndromes such as Smith Lemli –Opitz and Campomelic dysplasia also have 46 XY karyotype with  female or ambiguous genitalia.These occur due to mutations  in the autosomal genes DHCR7 (which codes for 7-dehydrocholesterol reductase) or it could be due to deletions in the autosomal gene SOX-9

• In some cases of 46XY there is a loss of SRY genes located on the Y chromosomes .  These SRY genes are responsible for the development  of the  male attributes.

• Sometimes, in a 46 XY individual, a  duplication of the dosage sensitive region (DSS) on the short arm of the X (Xp)  results in female external genitalia.

• Mutation in the gene DAX 1 is also associated with XY females

• Swyer syndrome  is a type of hypogonadism. Here  the functional gonads,the ovaries, are absent  but the person  resembles a normal female and has a  karyotype  46, XY.Androgen Insensitivity Syndrome(AIS) is the most common cause of 46, XY intersex. A person with AIS is insensitive to the male hormones( androgens). When an individual presents with a male genotype 46 XY  but appears more like a female, a case of ‘Androgen Insensitivity Syndrome’, also known as ‘testicular feminization’ should be suspected .

AIS individuals produce adequate amounts of testosterone but they lack the receptors that sensitize the body to the male hormone androgen. As  a result the person’s body cannot detect the androgens and, therefore, is unable to develop as male. These individuals grow as females and it really comes as a surprise to many of them when the abnormality is detected or when they find out that they are infertile.

c) True Gonadal Intersex.    

A person is said to be true gonadal intersex when both  testicular  and ovarian tissues are present.These tissues may be  found seperately or they may be present as a single ovotestis. The genotype may denote 46 XX, 46 XY or both. The external genitalia may appear to be male or female or it may be ambiguous . The underlying cause  of  this condition,  once referred to as  “true hermaphroditism”, is yet unknown.

d) Complex  Intersex Disorders

These intersex disorders are chrecterized by the impaired sexual development   and involves conditions such as Turners syndrome (45,XO), Klinefelter syndrome (47,XXY) and  super females (47,XXX).These individuals are not classically intersex but display deficiencies in their overall sexual development.