Causes & biology

Pattern hair loss is a biological process with a well-described mechanism: genetically sensitive follicles respond to dihydrotestosterone by shortening their growth phase and shrinking with each cycle. Other causes, from thyroid disease to medication and stress-related shedding, work differently and call for different responses. These guides explain the biology in plain language so that the logic of each treatment makes sense.

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  Causes & biology

  Vitamin D Deficiency and Hair Loss: What the Research Shows

  Can low vitamin D cause hair loss? What the studies in men show, the blood levels that count as low, when testing makes sense, and why supplements are not a treatment for pattern hair loss.

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  Causes & biology

  Low Ferritin and Hair Loss: What Your Iron Result Means

  Does low ferritin cause hair loss? What ferritin measures, why a normal lab range can still be low for hair, what the evidence shows in men, and why iron should not be taken without a test.

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  Causes & biology

  Does Thyroid Disease Cause Hair Loss?

  Both an underactive and an overactive thyroid can trigger diffuse shedding. How thyroid hormone affects the hair cycle and which labs to ask for.

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  Causes & biology

  Seasonal Hair Loss: Is Shedding Really Worse in the Fall?

  Why many people notice more shedding in late summer and fall, what the studies actually found, and how to tell a seasonal wave from loss worth evaluating.

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  Causes & biology

  Do Blood Pressure Medications Cause Hair Loss? Beta Blockers, ACE Inhibitors, and What the Evidence Shows

  Whether beta blockers, ACE inhibitors, and other antihypertensives cause hair loss, what case reports and labels show, and what to do if you shed.

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  Causes & biology

  Does Testosterone Therapy (TRT) Cause Hair Loss? What Men Should Know

  How TRT can accelerate pattern hair loss in genetically susceptible men, why delivery method matters, and how to protect your hair while on treatment.

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  Causes & biology

  Does Smoking Cause Hair Loss? What the Evidence Actually Shows

  Smoking is repeatedly associated with pattern hair loss in observational studies. What has been measured, the likely mechanisms, and how to weigh it.

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  Causes & biology

  Hair Loss After COVID or Illness: Why It Happens and When It Recovers

  Heavy shedding a few months after COVID or another illness is usually telogen effluvium, a temporary stress response. How long it lasts and what to do.

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  Causes & biology

  Do Statins Cause Hair Loss? What the Evidence Shows

  Hair loss is a rare and usually reversible side effect reported with statins. What the case reports and prescribing labels show and what to do if you shed.

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  Causes & biology

  Does Radiation Cause Hair Loss? What to Expect and When Hair Grows Back

  Why diagnostic imaging does not cause hair loss, how radiation therapy to the head leads to anagen effluvium, and when regrowth is likely versus permanent.

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  Causes & biology

  Does Gabapentin Cause Hair Loss? What the Evidence Shows

  Gabapentin is rarely linked to hair loss, and the evidence comes from a few case reports. What the literature shows and what to do if you shed on it.

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  Causes & biology

  Birth Control and Hair Loss: Why the Type of Progestin Matters

  How hormonal contraceptives may affect hair, why a progestin's androgenic activity matters more than the method, and what to do if you shed after a change.

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  Causes & biology

  Do Antidepressants Cause Hair Loss? What the Evidence Shows by Drug Class

  Which antidepressant classes are most often linked to shedding, how SSRI, SNRI, and bupropion hair loss works through telogen effluvium, and what to do.

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  Causes & biology

  Does Metformin Cause Hair Loss? What the Evidence Actually Shows

  The link between metformin and hair shedding, the role of vitamin B12 depletion, and what to do if your hair is thinning while taking it for diabetes.

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  Causes & biology

  Does Wearing a Hat Cause Hair Loss? What the Evidence Actually Shows

  Where the hat myth comes from, when headwear can cause real scalp problems like friction or folliculitis, and what actually drives pattern thinning.

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  Causes & biology

  Does Low Testosterone Cause Hair Loss? What the Evidence Actually Shows

  Why follicle sensitivity to DHT matters more than total testosterone, whether low T causes scalp hair loss, and how replacement therapy fits in.

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  Causes & biology

  Postpartum Hair Loss: Timeline, What Helps, and When to Worry

  Why postpartum shedding happens, the typical timeline for recovery, what may help, what is considered safe while breastfeeding, and when to ask a doctor.

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  Causes & biology

  What's New in Hair Loss Treatment Research: Stem Cells, JAK Inhibitors, Peptides, and More

  Experimental hair loss treatments in clinical research, including JAK inhibitors, stem cell and exosome approaches, and topical anti-androgens.

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  Causes & biology

  Does Creatine Cause Hair Loss? What the Evidence Actually Shows

  What the single 2009 creatine and DHT study really found, why it has not been replicated, and how to weigh the risk if you are prone to pattern hair loss.

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  Causes & biology

  What Is Androgenetic Alopecia? A Plain-English Guide to Pattern Hair Loss

  The medical name for pattern hair loss explained in plain terms: what causes it, how it progresses in men and women, and which treatments have evidence.

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  Causes & biology

  Nutritional Deficiencies That Cause Hair Loss: Iron, Vitamin D, Zinc, B12, and More

  Which deficiencies are actually linked to hair loss, including iron, vitamin D, zinc, and B12, what testing is useful, and when correcting one helps.

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  Causes & biology

  Do GLP-1 Weight-Loss Drugs Cause Hair Loss? What the Evidence Shows

  Why semaglutide, tirzepatide, and other GLP-1 medications are linked to shedding, the rapid weight loss mechanism behind it, and what to expect.

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  Causes & biology

  How the Hair Growth Cycle Works

  A clear walkthrough of anagen, catagen, telogen, and exogen, and why understanding the hair cycle helps explain pattern hair loss and treatment timelines.

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  Causes & biology

  What DHT Is and Why It Causes Pattern Hair Loss

  How 5-alpha-reductase converts testosterone to DHT, why genetically sensitive scalp follicles miniaturize in response, and what that means for treatment.

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  Causes & biology

  Stress and Hair Loss: Understanding Telogen Effluvium

  How physical and emotional stress can trigger telogen effluvium, a temporary form of diffuse shedding, how it differs from pattern hair loss, and recovery.