# What Causes Hair Loss? An Honest Breakdown of What’s Actually Happening
Most articles about hair loss are written to sell you something by paragraph three. This one isn’t. Before you spend a dollar on a serum, a supplement, or a clinic consultation, it’s worth understanding what’s actually happening on your head — because the cause determines the fix, and getting the cause wrong is how men waste years and thousands of dollars treating the wrong problem.
So: what causes hair loss? There isn’t one answer. There are about six, they often overlap, and the one you’re dealing with is usually identifiable from how your hair is leaving.
## The Big One: Genetics and DHT
Roughly 85% of male hair loss is androgenetic alopecia — male pattern baldness. It’s the receding hairline, the thinning crown, the slow retreat that follows a predictable map. This is genetic, and it’s driven by a hormone called dihydrotestosterone, or DHT.
DHT is a byproduct of testosterone. In men who are genetically sensitive to it, DHT binds to receptors in hair follicles and gradually shrinks them. Each growth cycle produces a thinner, shorter, weaker hair until the follicle eventually stops producing visible hair altogether. The follicle isn’t dead for a long time — it’s miniaturized. That distinction matters, because miniaturized follicles can sometimes be revived, and dead ones cannot.
If your hairline is receding at the temples or your crown is thinning while the back and sides stay full, this is almost certainly what you’re dealing with. The back and sides are spared because those follicles are genetically resistant to DHT — which, incidentally, is exactly why they’re the ones used in transplants.
## Stress and Telogen Effluvium
Here’s the cause people most often confuse with going bald: telogen effluvium. A major physical or emotional shock — surgery, illness, a crash diet, a death, a divorce, a serious fever — can push a large number of follicles into their resting phase at once. Two to three months later, they shed together, and you find frightening amounts of hair in the drain.
The good news is that this is usually temporary. Telogen effluvium is diffuse — hair thins all over rather than in a pattern — and it typically reverses within six to nine months once the trigger passes. If your hair started falling out in handfuls a couple of months after a stressful event, don’t panic-buy finasteride. You may simply need time.
## Hormones and Thyroid
Hormonal disruption beyond DHT can also drive shedding. Thyroid disorders — both overactive and underactive — commonly cause hair loss, as do imbalances in other sex hormones. This is why a decent doctor will run bloodwork before assuming your thinning is genetic. A thyroid problem responds to treating the thyroid, not to rubbing minoxidil on your scalp.
## Nutritional Deficiencies
Your hair is one of the first things your body sacrifices when it’s short on resources. Deficiencies in iron, zinc, protein, vitamin D, and biotin can all show up as thinning or increased shedding. This is especially common in men on aggressive cutting diets, vegetarians and vegans who haven’t planned their iron and protein intake, and anyone recovering from illness.
The important nuance: supplements only fix hair loss when a deficiency is the actual cause. If your levels are normal, megadosing biotin does nothing except produce expensive urine. Get tested before you guess.
## Medications and Medical Conditions
A long list of medications can cause hair loss as a side effect — blood thinners, beta-blockers, some antidepressants, retinoids, and of course chemotherapy, which causes the sudden, total shedding most people picture. Autoimmune conditions like alopecia areata cause distinct round bald patches rather than a receding pattern. Scalp infections such as ringworm (tinea capitis) cause hair to break off with flaking and scaling.
These causes look different from pattern baldness, which is the whole point of learning to tell them apart. Patchy, sudden, or itchy-and-flaky loss warrants a doctor, not a TikTok protocol.
## Things That Get Blamed but Mostly Don’t Cause Baldness
A few persistent myths deserve to be put down:
– Wearing hats does not cause hair loss. A hat tight enough to cut off follicle circulation would also cut off your scalp.
– Washing your hair doesn’t cause it either. The hairs in the drain were already in their shedding phase. Not washing just means they pile up and shed in bigger clumps later.
– Testosterone from the gym doesn’t make you bald. DHT sensitivity does. A man with high testosterone and no genetic sensitivity keeps his hair; a man with low testosterone and high sensitivity loses it.
What does contribute around the edges: chronic scalp inflammation, very tight hairstyles worn for years (traction alopecia), harsh chemical treatments, and smoking, which is genuinely associated with accelerated hair loss.
## How to Tell What’s Actually Happening to You
You can narrow it down fast by asking three questions:
1. What’s the pattern? Receding hairline and crown thinning with full back and sides points to genetic male pattern baldness. Diffuse thinning all over points to stress, hormones, or nutrition. Round patches point to alopecia areata.
2. What’s the timeline? Gradual over years is genetic. Sudden onset two to three months after a stressful event is telogen effluvium. Rapid patchy loss is autoimmune or infectious.
3. What changed? New medication, crash diet, major illness, or high-stress period in the months before? That’s your likely trigger — and triggers can often be removed.
## The Honest Bottom Line
If you’re losing hair in a pattern, gradually, with healthy hair on the back and sides, the cause is genetic and the clock is running — the earlier you intervene, the more you keep. If your loss is sudden, diffuse, patchy, or paired with other symptoms, get bloodwork and see a doctor before you start treating it as baldness, because you may be treating the wrong thing entirely.
Understanding the cause isn’t the exciting part of dealing with hair loss. But it’s the part that determines whether everything you do next is aimed at the right target.