Why Is My Hair Thinning? 7 Causes Beyond Genetics
When men notice thinning hair, they often assume it's just male pattern baldness. But not all hair loss is genetic. Thyroid problems, vitamin deficiencies, stress, and medications can all thin your hair—and these causes are often reversible.
Genetic vs Non-Genetic Hair Loss
Male pattern baldness (genetic): Receding hairline in an M-shape, thinning at the crown, progressive over years. The classic Norwood pattern.
Non-genetic hair loss: Often more diffuse (all over), may start suddenly, affects more than just the hairline and crown, may include other symptoms.
1. Thyroid Disorders
Both an underactive thyroid (hypothyroidism) and an overactive thyroid (hyperthyroidism) can cause hair loss. Thyroid hormones control the hair growth cycle—when levels are off, hair follicles may enter a prolonged "resting" phase and stop growing.
What It Looks Like
- •Diffuse thinning (all over, not just temples/crown)
- •Dry, brittle hair that breaks easily
- •May affect eyebrows and body hair too
- •Other symptoms: fatigue, weight changes, feeling cold/hot
What to do: A simple TSH blood test can screen for thyroid issues. If confirmed, treating the thyroid often reverses the hair loss within several months.
2. Telogen Effluvium (Stress-Induced Shedding)
Telogen effluvium (TE) is temporary, diffuse hair loss triggered by a major physical or emotional stressor. The stress pushes many hair follicles into the "resting" (telogen) phase at once. About 2-3 months later, all those hairs fall out together.
Common Triggers
- •Major illness (including COVID-19)
- •Surgery
- •High fever
- •Severe emotional stress (divorce, job loss, death of loved one)
- •Crash dieting or rapid weight loss
- •Starting or stopping medications
What It Looks Like
- •Sudden, noticeable shedding (handfuls in the shower)
- •Starts 2-3 months after the stressor
- •Diffuse thinning all over, not patterned
Good news: TE is temporary. Once the trigger is removed and your body recovers, hair regrows on its own—usually within 6-12 months. No treatment is typically needed except patience.
3. Nutritional Deficiencies
Your hair needs specific nutrients to grow. Deficiencies in iron, vitamin D, zinc, and other nutrients can cause or contribute to hair thinning.
Key Nutrients for Hair
Iron (Ferritin)
Low iron/ferritin is one of the most common non-genetic causes of hair loss. Optimal levels for hair: ferritin above 70 ng/mL.
Vitamin D
Vitamin D receptors are on hair follicles. Deficiency is very common and linked to hair thinning.
Zinc
Essential for hair growth and repair. Zinc deficiency can cause hair shedding.
Protein
Hair is made of keratin (protein). Severely low protein intake can impair hair growth.
Caution: Don't just take supplements blindly. Too much vitamin A, selenium, or vitamin E can actually cause hair loss. Get blood tests to identify real deficiencies before supplementing.
4. Medications
Many common medications can cause hair thinning as a side effect. Hair usually regrows after stopping the medication (with doctor guidance).
Medications That Can Cause Hair Loss
- •Blood thinners: Warfarin, heparin
- •Blood pressure meds: Beta-blockers, ACE inhibitors
- •Antidepressants: Some SSRIs and mood stabilizers
- •Cholesterol meds: Some statins
- •Acne medications: High-dose vitamin A (isotretinoin)
- •Chemotherapy drugs: (obvious, but worth mentioning)
- •Testosterone/anabolic steroids: Can accelerate genetic hair loss
What to do: Don't stop medications without talking to your doctor. Ask about alternatives if hair loss is a concern. Many drug-induced hair losses are reversible.
5. Alopecia Areata (Autoimmune Hair Loss)
Alopecia areata is an autoimmune condition where your immune system attacks hair follicles, causing patchy hair loss. It's not related to male pattern baldness.
What It Looks Like
- •Round or oval bald patches that appear suddenly
- •Smooth skin in the patches (no scarring)
- •Can occur on scalp, beard, eyebrows, or body
- •"Exclamation point" hairs at patch edges (short, tapered)
Treatment: Varies by severity. Mild cases may regrow on their own. Steroid injections, topical treatments, or newer JAK inhibitors (like baricitinib) can help more severe cases. See a dermatologist for evaluation.
6. Scalp Conditions
Inflammatory scalp conditions can damage follicles and cause hair loss, either temporarily or permanently depending on severity.
Common Scalp Issues
- •Seborrheic dermatitis: Scaly, red, itchy patches; dandruff-like flaking; can cause temporary thinning
- •Psoriasis: Thick, silvery scales; can affect hair growth in affected areas
- •Folliculitis: Infected/inflamed hair follicles; can cause localized loss
- •Fungal infections (ringworm): Causes patchy loss with broken hairs
If you have scalp symptoms (itching, flaking, redness, pain), see a dermatologist. Treating the scalp condition often resolves the hair loss.
7. Chronic Illness & Systemic Conditions
Various chronic health conditions can cause or contribute to hair thinning:
- •Diabetes: Poor blood sugar control affects circulation and can impair hair growth
- •Lupus: Autoimmune disease that can cause hair loss (often along the hairline)
- •Liver or kidney disease: Can disrupt nutrient absorption and hormone levels
- •Syphilis: Secondary syphilis can cause patchy "moth-eaten" hair loss
- •Eating disorders: Severe nutritional deficiency impairs hair growth
Not Sure What's Causing Your Hair Loss?
An online dermatology consultation can help identify the cause and recommend the right treatment.
How to Tell If It's Genetic vs Something Else
| Feature | Genetic (Male Pattern) | Non-Genetic |
|---|---|---|
| Pattern | Receding hairline, crown thinning | Diffuse (all over) or patchy |
| Onset | Gradual, over years | Often sudden or rapid |
| Family history | Usually yes | Not necessarily |
| Other symptoms | None (just hair loss) | Often (fatigue, scalp issues, etc.) |
| Trigger identifiable? | No specific trigger | Often yes (stress, illness, etc.) |
| Reversibility | Progressive without treatment | Often reversible |
Tests to Consider
If you suspect non-genetic hair loss, these blood tests can help identify the cause:
- •TSH: Thyroid function screening
- •Complete blood count (CBC): Anemia, infection
- •Ferritin: Iron stores (aim for 70+ for hair health)
- •Vitamin D: Common deficiency linked to hair loss
- •Zinc: If deficiency is suspected
- •Testosterone, DHT: If hormonal cause suspected
- •ANA: If autoimmune disease suspected
Key Takeaways
- 1. Not all hair loss is genetic — many causes are treatable or reversible
- 2. Thyroid disorders are a common culprit — a simple TSH test can screen for this
- 3. Telogen effluvium (stress shedding) is temporary — hair regrows once the trigger resolves
- 4. Check iron, vitamin D, and zinc — deficiencies are common and fixable
- 5. Review your medications — many drugs can cause hair loss as a side effect
- 6. Patchy hair loss may be alopecia areata — see a dermatologist
- 7. Diffuse or sudden hair loss deserves investigation — don't assume it's just genetics
- 8. Treating the underlying cause often restores hair
Medical Disclaimer: This article is for informational purposes only and does not constitute medical advice. Sudden or unexplained hair loss should be evaluated by a healthcare provider to rule out underlying conditions.