Your Hair Loss Has a Genetic Reason. Here's What Science Shows.

The AR gene produces the androgen receptor, a protein on the surface of hair follicle cells that receives signals from DHT, the hormone that can shrink hair follicles. Think of it as a lock, and DHT as the key. The sensitivity of this lock determines whether your follicles will miniaturize in response to DHT in your bloodstream.

Your AR gene has a variable section called a CAG repeat, which can range from 8 to 30+ copies. Shorter CAG repeats mean a more sensitive androgen receptor, making your hair follicles more responsive to DHT-mediated miniaturization. This is one of the strongest genetic predictors of male and female pattern baldness. People with very short CAG repeats can lose hair even with modest DHT levels, while people with longer repeats may never experience significant hair loss despite higher DHT.

If you have a shorter CAG repeat, you’re experiencing hair loss that feels out of proportion to your DHT levels. You may have tried DHT-blocking treatments with mixed results because the underlying issue isn’t how much DHT you’re producing; it’s how responsive your follicles are to whatever DHT is present. This also means hormonal changes can accelerate your hair loss more dramatically than they would for someone with a longer repeat.

The SRD5A2 gene produces the enzyme 5-alpha reductase type 2, which converts testosterone into DHT in your scalp and hair follicles. DHT is the primary driver of androgenetic alopecia, the most common form of hair loss. The amount of DHT your scalp produces determines much of your hair loss risk.

The V89L variant, present in roughly 30-40% of people, affects how efficiently this enzyme works in your hair follicles and scalp. Some variants increase DHT production in the scalp while others reduce it. If your variant increases local DHT production, your follicles are being bathed in higher concentrations of this miniaturizing hormone every day. Even if your blood testosterone is normal, your scalp DHT may be significantly elevated.

You may notice that your hair loss accelerated during puberty or after starting certain medications or supplements that raise testosterone. You might have tried topical minoxidil with only modest results because the underlying issue is your scalp is overproducing DHT. This is especially true if you’re also carrying certain AR variants that make your follicles particularly sensitive to whatever DHT is present.

The VDR gene produces the vitamin D receptor, a protein that sits on hair follicle cells and receives signals from activated vitamin D. When vitamin D binds to this receptor, it tells the follicle to transition from the resting phase into active growth. VDR dysfunction disrupts this critical cycle and can stall follicles in their resting state.

Common VDR variants like BsmI and FokI, present in roughly 30-50% of people depending on ancestry, impair the receptor’s ability to respond to vitamin D signaling. This means even if your blood vitamin D levels are adequate, your hair follicles may not be receiving the signal to grow. Follicles get stuck in telogen, the resting phase, and never transition back into anagen, the growth phase. You end up with diffuse hair shedding and slow regrowth.

If you have a VDR variant, you may have had your vitamin D level checked, found it to be normal or even high, and been confused why your hair is still thinning. The issue is not vitamin D availability; it’s your follicles’ ability to respond to it. You may also notice your hair loss worsens in winter or with reduced sun exposure, suggesting a seasonal pattern.

The MTHFR gene produces an enzyme that converts folate into its active form, methylfolate. This active form is essential for methylation reactions throughout your body, including the rapid cellular turnover required to build new hair in the follicle matrix. Hair follicles are among the fastest-dividing cells in your body, and they demand a constant supply of methylation capacity to replicate DNA and build new hair shaft.

The C677T variant, carried by roughly 40% of people with European ancestry, reduces MTHFR enzyme efficiency by 40-70%. This means your hair follicles are starved of the methylation cofactors they need to divide rapidly and produce new hair. You can eat a perfect diet with plenty of folate and still be functionally depleted at the cellular level because your cells cannot convert folate into the active form they need.

If you have an MTHFR variant, you may notice diffuse hair thinning rather than clear patch loss. Your hair may grow slowly, feel fragile, or lack volume and thickness. You’ve probably tried regular folic acid supplements with minimal improvement because your body struggles to convert them. Standard bloodwork may show normal folate levels, making the problem invisible to your doctor.

The SOD2 gene produces superoxide dismutase 2, a critical antioxidant enzyme that lives inside your mitochondria and neutralizes reactive oxygen species. Hair follicles have extremely high metabolic demand; they’re constantly dividing and requiring massive amounts of energy from mitochondria. This high energy production generates free radicals, which must be neutralized or they damage the follicle’s DNA and proteins.

The Val16Ala variant, present in roughly 40% of people with the homozygous variant, impairs SOD2 enzyme activity and reduces mitochondrial antioxidant defense. This means oxidative stress accumulates in your hair follicle cells, damaging the proteins and DNA required for hair growth. The follicles become inflamed and senescent, unable to divide efficiently or produce healthy hair. Over time, this chronic oxidative stress accelerates hair loss and ages the scalp.

If you have an SOD2 variant, your hair may feel prematurely aged; it may break easily, lack elasticity, or appear dull and lifeless. You may notice your scalp is frequently inflamed or itchy, even though you have no diagnosed skin condition. Your hair loss or poor hair quality may accelerate with stress, poor sleep, or high-intensity exercise, all of which increase oxidative stress.

The FLG gene produces filaggrin, a structural protein that holds together the outermost cells of your skin barrier. Think of your scalp skin barrier as a brick wall; filaggrin is the mortar holding the bricks together. When filaggrin is missing or defective, the mortar crumbles and the bricks separate. Water leaks out, irritants and bacteria leak in, and inflammation follows.

The loss-of-function variants R501X and 2282del4, present in roughly 10% of people with European ancestry, delete parts of the filaggrin gene entirely. This means your scalp barrier is fundamentally compromised; it cannot hold moisture or defend against irritants. Your scalp becomes a chronically inflamed, leaky, reactive environment. This chronic inflammation accelerates hair loss and makes your scalp extremely sensitive to products, stress, and dietary triggers.

If you have an FLG variant, your scalp is probably itchy, flaky, or prone to fungal or bacterial overgrowth. Your hair loss may be accompanied by visible scalp inflammation, sensitivity to products, or seasonal flares. You may have been told you have eczema or seborrheic dermatitis, which are hallmark FLG-related conditions. Standard treatments for hair loss won’t help because your primary problem is scalp barrier failure, not follicle miniaturization.