The Androgen Receptor gene has been identified as a major determinant of androgenetic alopecia (AGA) or male pattern baldness. Certain variants of the nucleotide sequence on the Androgen Receptor gene, known as CAG repeats, appear to determine androgen sensitivity in men. Lower numbers of CAG repeats have been associated with increased androgen sensitivity. This sensitivity and associated genotype have been associated with a myriad of physiologic effects. In particular to hair loss, it has now been shown in 2 independent studies from 2 major research groups in Japan, that a lower number of CAG repeats also impacts patient responsiveness to medication therapies for AGA.

Currently one of the most widely prescribed medications, finasteride, works by blocking the production of the androgen called DHT (dihydrotestosterone), the hormone responsible for hair loss in androgenetic alopecia. For many years finasteride therapy, which blocks the enzyme 5-alpha reductase from converting testosterone into dihydrotestosterone (DHT), has become a mainstay to treat AGA. This treatment is an effective means to stabilize hair loss (85%) and in some cases to strengthen and re-grow lost hair (66%). Other medication therapies in the same drug family, such as dutasteride, have been used off label for this purpose too. However, there is a side effect profile to these drugs, albeit only a reported 3% for finasteride, resulting in various types of sexual dysfunction, as well as other quite rare effects of breast tenderness or enlargement (gynecomastia). Despite the small percentage of affected patients the threat of a side effect deters many patients from pursuing a medication trial when they remain uncertain that the risk will be justified by a benefit.

Furthermore, there are patients with existing degrees of hair loss who would seek the more invasive therapy of hair restoration surgery, but are often discouraged by hair restoration doctors and dermatologists from proceeding proactively when they have had no or only a limited trial of medical therapy. The rationale for waiting is that with sufficient time, medical therapy could reverse the appearance of hair loss and obviate surgical treatment. Because hair grows in cycles, in most cases it takes 3 months before the medication can be seen to decrease shedding and 6 months to determine if it may have an affect on visible re-growth. Patients whose genotype makes it likely they will not be significant responders may wait for many months in frustration to see if the medication will work for them. And all the time they are waiting they may be losing more hair even as their hair loss becomes more visible to themselves and others. Despite the high response rate to medication therapy, there exists a desire to predict more accurately who will respond as a means for doctors and patients to determine if it is worth the time, expense, and risk of medication therapy.

Genetic sequencing of the androgen receptor gene offers a novel approach to assist doctors and patients in determining a patient's androgen sensitivity and degree of response to medications such as finasteride (Propecia and Proscar) which can block the production of the potent androgen known as DHT. The new HairDX (RxR) Genetic Test has been designed to determine the number of CAG repeats on a patient's androgen receptor gene, and thereby offers a means to determine the response to medication therapy to assist patients and doctors in decision making when determining the most time and cost effective approach to treating a patient's hair loss in AGA.

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