Your Hair and Skin Problems May Be Written in Your DNA.

The AR gene encodes the androgen receptor, a protein that sits on the surface of hair follicle cells and listens for signals from DHT (dihydrotestosterone). Think of it as the lock, and DHT as the key. When DHT binds to the androgen receptor, it tells the follicle to shrink. This is normal in some parts of your body, but in the scalp of genetically predisposed people, it causes follicles to miniaturize, producing thinner and shorter hairs over time. The AR gene’s sensitivity directly determines whether DHT will drive hair loss or pass by harmlessly.

Your AR gene has a variable number of CAG repeats. Shorter CAG repeats make your androgen receptor more sensitive to DHT, meaning your hair follicles respond more aggressively to the hormone. This variant isn’t rare. Roughly 30-40% of men with pattern hair loss carry short CAG repeats that amplify DHT’s effect. The number of repeats is inherited and fixed; you cannot change it. But understanding your repeat length tells you exactly how much DHT sensitivity you’re dealing with.

If you carry short CAG repeats, your hair follicles are essentially “listening too closely” to DHT signals. Even normal testosterone levels get converted to DHT and trigger miniaturization. You might notice thinning starting earlier than in your family, or progressing faster than expected. Hair on your scalp thins while body hair may be unaffected, because follicles in different locations have different androgen receptor density. Knowing your AR status tells you whether DHT management should be a priority in your protocol.

The SRD5A2 gene encodes 5-alpha reductase type 2, the enzyme that converts testosterone into DHT. It’s a critical step in the biochemistry of androgenic alopecia. Most of the DHT that affects your hair follicles is produced locally in the scalp by this enzyme. The more active your 5-alpha reductase, the more DHT gets produced, and the more your hair follicles miniaturize if you’re genetically predisposed.

The V89L variant (rs523349) is the most studied polymorphism in this gene. Roughly 30-40% of people carry variants that increase 5-alpha reductase activity, boosting local DHT production in the scalp. Even if your androgen receptor sensitivity is average, higher DHT production can still drive significant hair loss. Some variants reduce enzyme activity, offering protective effect. But if you carry activity-increasing variants, your scalp is essentially manufacturing more of the hormone that shrinks follicles.

You might notice hair thinning that started young, or that progressed despite normal or even low-normal testosterone levels. That’s a sign your body is very efficiently converting whatever testosterone you have into DHT. Finasteride (Propecia) specifically blocks this enzyme, which is why it’s one of the few medications with proven efficacy for pattern hair loss. Knowing your SRD5A2 status tells you whether you’re dealing with a DHT production problem, a DHT sensitivity problem, or both.

The VDR gene encodes the vitamin D receptor, a protein that your cells use to respond to vitamin D (calcitriol). Vitamin D is not just a vitamin; it’s a hormone that regulates hundreds of biological processes. In hair follicles, vitamin D is essential for the anagen phase, the growth phase where the follicle is actively producing hair. When vitamin D receptor function is impaired, hair follicles get stuck in resting phases or shift into shedding phases prematurely.

Common VDR variants include BsmI and FokI polymorphisms. Roughly 30-50% of people carry VDR variants that reduce receptor sensitivity to vitamin D signaling. This means your hair follicles aren’t hearing the vitamin D signal as loudly, even if your blood vitamin D levels look adequate. You can have a normal 25-OH vitamin D level and still have follicles that aren’t responding properly because your receptor is less efficient. This is especially relevant in alopecia areata, an autoimmune hair condition where VDR variants are overrepresented.

You might experience diffuse shedding, telogen effluvium, or follicles that won’t transition back into growth phase after stress or illness. Hair might feel finer overall, or you might have cycles of shedding that respond to seasonal vitamin D changes. If you live in a region with limited sun exposure, or if your vitamin D levels are borderline despite supplementation, VDR variants could be part of the explanation.

The MTHFR gene encodes an enzyme central to the methylation cycle, a metabolic pathway that affects virtually every cell division and detoxification process in your body. In hair follicles, methylation drives the rapid cell turnover required for hair growth. Hair is one of the fastest-growing tissues in your body; follicle cells divide thousands of times. This process demands constant methylation reactions. If your methylation cycle is impaired, follicle cells regenerate more slowly, and hair growth slows with it.

The C677T variant is carried by roughly 40% of people of European ancestry, and it reduces MTHFR enzyme efficiency by 40-70%. This creates a bottleneck in the methylation cycle. Your cells can still function, but they’re working at a reduced capacity. Over time, this affects cell turnover in hair follicles. You might not lose hair from androgenic mechanisms (DHT sensitivity), but you experience diffuse thinning because follicles simply aren’t regenerating as fast as they should.

You might notice that your hair feels thinner overall, without distinct male or female pattern baldness. Hair might be finer in texture, or growth might be slower (you need haircuts less frequently, but you also shed more because the growth cycle is extended). This is especially noticeable if you also have poor methylation-supporting nutrition (low B12, low folate, high homocysteine). Focusing on methylation support often produces noticeable improvements in hair texture and density.

The SOD2 gene encodes superoxide dismutase 2, a mitochondrial antioxidant enzyme. Your cells generate oxidative stress as a byproduct of energy production. Excess oxidative stress damages proteins, lipids, and DNA, accelerating aging. Skin cells are especially vulnerable because they’re exposed to UV radiation, which generates reactive oxygen species. SOD2 is your cells’ primary defense against this damage. Hair follicles also rely on mitochondrial health; follicles are metabolically active and vulnerable to oxidative stress.

The Val16Ala variant (rs4880) is carried by roughly 40% of the population in homozygous form, and it reduces SOD2 enzyme efficiency. This means your cells have a lower antioxidant capacity. Oxidative stress accumulates more readily. Over years, this accelerates skin aging, increases photosensitivity, and can worsen inflammatory skin conditions like eczema or psoriasis. In hair follicles, oxidative stress contributes to follicle dysfunction and premature aging of the follicle.

You might notice your skin ages faster than expected, with earlier wrinkles, age spots, or uneven pigmentation. Inflammatory skin conditions might be harder to control despite good skincare. Hair follicles might be more sensitive to stress, producing more shedding in response to oxidative triggers. Your skin might feel more reactive overall, more prone to redness or sensitivity. If you spend time in the sun, or live in a high-UV environment, SOD2 variants become especially relevant.

The FLG gene encodes filaggrin, a protein that is absolutely essential for skin barrier function. Filaggrin forms the structural framework of the outermost layer of skin (the stratum corneum). It holds moisture in and keeps irritants and pathogens out. Loss-of-function variants in FLG are the strongest genetic predictor of eczema and atopic dermatitis. People with FLG mutations have a fundamentally compromised skin barrier; they lose water through their skin at a much higher rate than people with intact FLG.

Loss-of-function variants like R501X and 2282del4 are carried by roughly 10% of people of European ancestry, and they severely impair filaggrin production. Even heterozygous carriers (one mutant copy) show measurable barrier dysfunction. The barrier defect is not reversible through diet or lifestyle alone; it’s written into the DNA of your skin cells. However, this doesn’t mean you’re doomed to eczema. It means you need a barrier-repair protocol that accounts for the structural deficit.

If you carry FLG variants, you probably experience dry, sensitive, itchy skin. Your skin might react to products that don’t bother other people. You might have recurring eczema, especially in creases (neck, elbows, behind knees, between fingers). Lotions that work for others might not help you much, because the barrier problem is structural, not just about surface moisture. You might notice your skin gets worse in winter (low humidity) or with exposure to irritants (fragrances, harsh soaps, chlorine). Barrier-focused skincare becomes non-negotiable.