Your Hair Is Falling Out, and Stress Isn't the Only Culprit.

The androgen receptor is the lock on your hair follicle cells. DHT is the key. When DHT binds to this receptor, it signals hair follicles to shrink (miniaturize). The strength of this lock is determined by a repetitive genetic sequence called a CAG repeat. Shorter repeats mean a tighter lock: DHT binds more easily and more strongly.

If you carry a shorter CAG repeat in your androgen receptor gene, your hair follicles are exquisitely sensitive to DHT. This is common and inherited, often running in families where early male baldness is the pattern. Roughly 30-40% of men with androgenetic alopecia carry particularly sensitive androgen receptors. For you, this means that even normal DHT levels may trigger significant miniaturization, and stress that slightly elevates DHT becomes the tipping point.

You may have noticed that your hair loss follows a pattern similar to your father’s or grandfather’s. You might have lost hair earlier than peers, or faster. If you’ve noticed thinning most prominently at your crown or temples, this gene is likely involved. For women with the shorter CAG repeat, hair loss often worsens after hormonal shifts (postpartum, perimenopause, or when taking hormonal birth control).

This enzyme converts testosterone into DHT, the hormone that drives hair loss in genetically susceptible follicles. You produce DHT for a reason: it’s necessary for beard growth, body hair, and male sexual function. But you need only so much. The SRD5A2 V89L variant changes how efficiently this enzyme works.

Carriers of the variant produce DHT at different rates than the standard version. Approximately 30-40% of the population carries the V89L variant, which can increase DHT production or alter the tissue distribution of DHT. For people with both a sensitive androgen receptor and elevated DHT production, the combined effect is dramatic: hair follicles are bombarded with a hormone they’re primed to respond to aggressively.

You might notice that your hair loss accelerated in your twenties or thirties when DHT production peaks. Stress that raises your overall testosterone levels then compounds the problem by flooding your follicles with more substrate for DHT production. If you’re female and carry this variant, you may experience more pronounced hair loss during the luteal phase of your cycle, when androgens naturally rise slightly.

Estrogen is protective for hair. It keeps hair follicles in the growth phase and prevents premature shedding. The estrogen receptor (ESR1) is where estrogen binds to exert this protective effect on follicles. But not everyone’s estrogen receptor works equally well. The PvuII and XbaI variants in ESR1 change how sensitive your hair follicles are to estrogen’s protective signal.

If you carry variants that reduce estrogen receptor sensitivity, your hair follicles don’t respond as robustly to estrogen’s growth-promoting effects. Roughly 40% of the population carries at least one variant affecting estrogen receptor function. This matters enormously for women approaching perimenopause or after menopause, when estrogen drops and this genetic vulnerability becomes obvious. It also matters for younger women: even with normal estrogen levels, if your receptors aren’t working well, you won’t get full protection.

You might have noticed hair loss worsening after stopping hormonal birth control, during the luteal phase, or as you moved closer to perimenopause. Women with poor ESR1 function often experience telogen effluvium (diffuse shedding) triggered by hormonal shifts that wouldn’t affect someone with a better receptor. If you’ve had postpartum hair loss that was severe or prolonged, this gene may explain why.

This enzyme controls methylation, one of your body’s most critical cellular processes. Methylation is required for DNA synthesis, cell division, and the rapid regeneration of tissues like hair. Your hair follicles are among the fastest-dividing cells in your body, so they depend heavily on efficient methylation. The MTHFR C677T variant reduces this enzyme’s activity significantly.

If you carry the C677T variant, your cells convert folate into the active form needed for methylation at 40-70% efficiency compared to the standard version. Approximately 40% of people of European ancestry carry at least one copy. This means your hair follicles are regenerating more slowly than optimal. Hair that should transition smoothly through growth cycles instead stalls. The result is diffuse thinning rather than the patterned loss of androgenetic alopecia, though many people have both problems simultaneously.

You might notice that your hair looks thinner overall, less dense, and breaks more easily. You may also experience fatigue, brain fog, or slow wound healing, all signs that your methylation is struggling. If adding biotin, collagen, or regular vitamins hasn’t helped, it’s because you’re not addressing the root: you need the activated form of folate that your broken MTHFR can’t make efficiently.

Vitamin D receptor is the lock that vitamin D turns to communicate with your hair follicles and tell them to enter the growth phase. Without adequate VDR function, your hair follicles stay stuck in the resting (telogen) phase or transition prematurely out of the growth phase. The BsmI, FokI, and TaqI variants in VDR affect how well this signaling works.

If you carry VDR variants that reduce receptor sensitivity, your follicles don’t respond as robustly to vitamin D’s growth signal. Approximately 30-50% of the population carries at least one of these variants. This is particularly critical for hair loss triggered by stress, because stressed follicles are more dependent on vitamin D signaling to remain activated. Someone with a poorly functioning VDR cannot simply supplement vitamin D and expect full benefit; the receptor isn’t listening well enough.

You might have noticed that your hair loss is diffuse and cyclical rather than patterned. You may also be prone to infections, slow wound healing, or muscle weakness, all signs of VDR dysfunction. If you live in a northern climate or have limited sun exposure and supplement vitamin D but still lose hair, this gene may be why.

The HFE gene controls how your body absorbs and stores iron. Iron is critical for hemoglobin, which carries oxygen to your hair follicles. But iron balance is delicate: too little and follicles starve for oxygen; too much and iron accumulates in tissues, creating oxidative stress that damages the follicle. The C282Y and H63D variants in HFE disrupt this balance.

If you carry HFE variants, your iron absorption and storage may be dysregulated, either causing iron accumulation or creating functional iron deficiency. Roughly 10% of people carry one copy of C282Y, though full hemochromatosis (two copies) is less common. The problem is that standard iron panels often miss this; you can have technically normal serum iron but functionally depleted iron in your hair follicles, or conversely, accumulated iron that your blood work doesn’t reveal.

You might have noticed that you’ve had iron supplements recommended by one doctor but another says your iron is normal. You may experience fatigue, joint pain, or brain fog alongside hair loss. If you’re female and have had heavy periods, HFE variants can exacerbate iron loss. If you’re male or postmenopausal, the opposite can happen: iron accumulates silently and damages follicles through oxidative stress.