AGA susceptibility is largely determined by genetics, though the environment may also play a minor role. Androgen receptor polymorphisms probably make the key determination for androgen responsiveness, but 5α reductase, aromatase, and sex hormone binding globulin (SHBG) genes may also contribute along with other hormone metabolism associated genes.8
While the complete genetic picture is not clear, at least one company claims to have a gene polymorphism based diagnostic test (HairDX™) that will predict the chances of future AGA development.9,10 For young patients concerned about hair loss this test may help to define the value of early treatment initiation. Perhaps of more immediate practical significance, a test that predicts responsiveness to treatment with finasteride is also available.11 In women, serum ferritin levels may also be assessed to determine iron deficiency, thyrotropin levels may be evaluated to rule out thyroid dysfunction, and free testosterone is assessed when androgen excess is suspected. If serum ferritin is low, iron supplementation has been recommended as an enabler of response to other treatments.2
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