Recent advances in human genetics empower researchers to discover the genetics of many common disorders. As genetic science is evolving at a rapid pace, new discoveries are made almost daily.

HairDX is committed to providing the latest in genetic discoveries to individuals. Although the causative genes for Androgenetic Alopecia (AGA) are not yet fully characterized, prevailing evidence supports a polygenic model based primarily on the fact that autosomal and single gene inheritance theories are not supported by observed patterns.

Evidence against an autosomal pattern are the observed phenotypic prevalence of AGA in families which does not fit the expected bimodal distribution. A single gene hypothesis would yield an expected prevalence of around 1:1000, far less than the high percentage of affected males seen in population studies.

Efforts to identify the causative genes have focused on those known to be related to mechanisms of hair growth. However, tests failed to reveal any association between the suspect genes and AGA, with one notable exception. There have been 4 published studies involving over 2000 patients which document the association between AGA and the androgen receptor (AR) gene on the X chromosome.

A particular polymorphism or variant allele at the AR site has been shown to be associated with a higher risk of developing AGA (approximately 70%) and, conversely, a protective, less frequent allele which has been associated with a very low likelihood of developing AGA (approximately 70% probability of not developing AGA).(1-4)

Furthermore, integrating the family history of AGA from a patient’s father can help improve the predictive value of the HairDX test. For the purpose of family history, even a moderate degree of AGA (Hamilton-Norwood Scale 2A or greater, receding hairline) is considered positive. Those with a father having a history of AGA who test positive for the AR variant have greater than an 80% chance of developing AGA. Those with a father without any history who test negative for the AR variant have greater than a 90% chance of not developing AGA.

The value of this test is that it offers the first credible, reproducible screen for assessing an increased risk for the development of AGA prior to the onset of symptoms. It also allows patients with the low risk AR variant and a strong family history of AGA to learn their risk of developing AGA, which is small nevertheless. Because of the limitations in specificity at this time a confirmation test should be used to determine the need for medical therapy. Confirmation tests include the “pull test”, or one of the newer trichometric methods of assessing Anagen:Telogen ratio. A normal A:T ration is 12:1, as AGA progresses this drops to 5:1. Documentation of a falling A:T ratio indicates the onset of AGA. Although the sensitivity of the genetic screen is high, the specificity reduces the predictive value, so how is this test better than watchful waiting? First of all, studies have shown that men are reluctant to visit doctors unless they think that something is “wrong”, (2007 Harris Interactive Online Survey for AAFP) and without visible thinning or some other warning, many won’t seek medical therapy or advice. Furthermore, many patients shed very gradually, they do not see hair in the sink, on the pillow or on their clothes and thus may not notice hair loss is occurring, once again, until a pattern has developed. Allowing these patients an opportunity to become aware of their risk, can increase vigilance, allow them to learn about their options, and to seek more frequent medical assessment until medical intervention is warranted. Conversely, those patients who will suffer rapid shedding, may not do so in a gradual, stepwise pattern of shortened growth cycles, but rather a sudden change from anagen to telogen and then hair loss without gradual miniaturization. This group of patients will need intervention very quickly to intercede in the hair loss process, and in the absence of planning in advance, it is likely that delays in getting in to see their doctor and instituting therapy will result in unnecessary hair loss and perhaps alternate more expedient but perhaps less useful therapies in the meantime.

The continued success of many ineffective, unapproved treatments for hair loss suggests that many patients have not been educated by medical doctors regarding effective treatment options. A relatively inexpensive screening test, which is non invasive and easy to perform, and highly reproducible, can potentially attract patients to their doctor to seek expert advice. By adhering to ethical principles that dictate patients' interests, other family members with hair loss may gain confidence and become willing to investigate their options. Furthermore, while it is true that some patients who initiate medical therapy may never develop significant hair loss or require future hair restoration surgery, there will be those who do not seek or stay on medical therapy despite their known risks. For example, consider the fact that cholesterol screening and lipid lowering medications while life saving for many, have not eliminated the need for coronary artery bypass surgery. Likewise, hair restoration surgery will continue, for now, to be the most effective therapy for replacing areas of bald scalp.

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