Some epidemiological studies have associated a shorter CAG repeats with hyperandrogenic syndromes, such as precocious pubarche or polycystic ovary syndrome (PCOS).[7–11] In addition, the AR gene is subjected to X inactivation in females and, given its common polymorphism, it is the one usually used to detect the degree of X chromosome inactivation in women.[12] The pattern of gene inactivation may affect the phenotype as well, since it determines which of the 2 alleles has higher functional effect in a given cell. Here, AR is linked to polycystic ovary syndrome.