Androgen Insensitivity Syndrome

Androgen insensitivity syndrome (AIS) is a condition that results in the partial or complete inability of the cell to respond to androgens. The unresponsiveness of the cell to the presence of androgenic hormones can impair or prevent the masculinization of male genitalia in the developing fetus, as well as the development of male secondary sexual characteristics at puberty, but does not significantly impair female genital or sexual development. As such, the insensitivity to androgens is only clinically significant when it occurs in genetic males (i.e. individuals with a Y chromosome, or more specifically, an SRY gene).


AIS is divided into three categories that are differentiated by the degree of genital masculinization: complete androgen insensitiviy syndrome (CAIS) is indicated when the external genitelia is that of a normal female, mild androgen insensitivity syndrome (MAIS) is indicated when the external genitelia is that of a normal male, and partial androgen insensitivity syndrome (PAIS) is indicated when an external genitelia is partially, but not fully masculinized.


Androgen insensitivity syndrome is the largest single entity that leads to 46, XY undermasculinization.


source: http://en.wikipedia.org/wiki/Androgen_insensitivity_syndrome


From the lecture:
Sexual differentiation occurs during the embryonic stage of prenatal development. Before differentiation, we are the same; every embryo has female characteristics by default. Genetic activity on Y sex chromosome causes the testes to begin to differentiate. Once testes develop, they produce androgens (male sex hormones). The most important sex hormone is testosterone which promotes growth of male sexual characteristics and sperm. Ovaries differentiate if Y chromosome is absent. By 4 months, distinct external genital structures are formed.
In absence of androgens, female reproduction system develops (initial undifferentiated structures). Therefore an embryo with a pair of XY chromosomes should be exposed to androgens in order to be able to develop as a male. If the embryo is not exposed to androgens, female develops however the chromosome structure is.


Here are some pictures about androgen insensitivity syndrome:

Caster Semenya:

Mokgadi Caster Semenya (born 7 January 1991) is a South African middle-distance runnerand world champion. Semenya won gold in the women's 800 metres at the 2009 World Championships with a time of 1:55.45 in the final.

Following her victory at the 2009 World Championships, questions were raised about whether Semenya has an physical condition that might give her an unfair advantage over other female racers. She was withdrawn from international competition until 6 July 2010 when the IAAF cleared her to return to competition. In 2010, the British magazine New Statesman included Semenya in its list "The World's 50 Most Influential Figures 2010".

source: http://en.wikipedia.org/wiki/Caster_Semenya