In addition to detecting for latent risk of AGA (male pattern baldness) in the future, a test determines whether the person is receptive (i.e., will it produce effects if ingested) to Propecia (active ingredient: finasteride).
This can be used for preventive treatment of AGA. The test simply requires swabbing the mucous membranes inside your mouth with a cotton swab. The test costs 15,000 JPY. Note that this exam is not mandatory and only for those who elect to take it.
Humans have twenty-three chromosomes, with one of these being the sex chromosome. Sex chromosomes are either X or Y; inheriting an X chromosome from both the mother and father leads to the female sex, while inheriting an X chromosome from the mother and Y from the father leads to the male sex.
AR genes are genes in which the X chromosome is found; it contributes to receptivity to male hormones and is considered to be one factor contributing to the risk of AGA and susceptibility to finasterides.
AR genes are expressed in repeating sets of three bases, such as C-A-G or G-G-C.
Through genetic testing, the total repetitions of CAG and GGC are used to determine the risk of AGA, and the repetitions of standalone GGC used to determine receptivity to finasteride. Specifically, the more repetitions of CAG and GGC, the less susceptible one is to AGA, and vice versa.