What are the causes of hair loss in men?

Causes of Hair Loss in Men

Hair loss in men is primarily caused by androgenetic alopecia (male pattern baldness), which accounts for the vast majority of cases, followed by alopecia areata, telogen effluvium, drug-induced hair loss, infections (particularly tinea capitis), scarring alopecias, and less commonly systemic diseases or behavioral disorders like trichotillomania.

Primary Causes

Androgenetic Alopecia (Male Pattern Baldness)

This is the dominant cause of hair loss in men, affecting up to 80% of males by age 80 1, 2. The pathophysiology involves:

• Androgen-dependent progressive miniaturization of hair follicles, converting terminal hairs to vellus hairs
• Genetic predisposition with multiple genes involved, including the androgen receptor (AR), HDAC4, HDAC9, and WNT10A 3
• Family history is the strongest predictor, with paternal family history conferring 2.22 times increased risk 4

The condition is clinically distinct with a characteristic pattern of hair loss beginning at the temples and vertex.

Alopecia Areata

This is a chronic inflammatory autoimmune disease affecting the hair follicle 5. Key features include:

• T-lymphocyte mediated destruction of immune privilege in hair follicles 5
• Presents as circumscribed patches of hair loss with characteristic "exclamation mark hairs" at margins
• 20% have family history indicating genetic predisposition involving MHC and cytokine genes 5
• No sex preponderance, can occur at any age
• 34-50% recover within 1 year, though 14-25% progress to total scalp hair loss (alopecia totalis) 5

Telogen Effluvium

A common cause of diffuse hair shedding triggered by:

• Fever, severe illness, hemorrhage
• Significant stress
• Medications 6
• Metabolic disturbances

This represents a shift of hair follicles into the telogen (resting) phase, resulting in increased shedding 2-3 months after the triggering event 5, 7.

Secondary Causes

Drug-Induced Hair Loss

Multiple mechanisms exist 6:

• Anagen arrest (chemotherapy agents)
• Telogen effluvium (various medications)
• Accentuation of androgenetic alopecia by androgenic medications

A thorough medication history is essential, looking for temporal association between drug initiation and hair loss onset.

Infectious Causes

Tinea capitis (scalp ringworm) can mimic other forms of alopecia 5. The scalp may show subtle inflammation. Fungal culture is indicated when this is suspected.

Scarring Alopecias

These include 7:

• Frontal fibrosing alopecia
• Discoid lupus erythematosus
• Lichen planopilaris
• Folliculitis decalvans

These conditions permanently destroy hair follicles and require scalp biopsy for definitive diagnosis.

Behavioral/Psychiatric

Trichotillomania (compulsive hair pulling) is an important differential 5. Distinguishing features include:

• Incomplete hair loss pattern
• Broken hairs remain firmly anchored in scalp (still in anagen phase)
• May coexist with alopecia areata

Systemic Diseases

Less common causes include 5:

• Systemic lupus erythematosus (requires serology)
• Secondary syphilis (requires serology)
• Thyroid disorders
• Nutritional deficiencies (though routine iron testing is not recommended in men) 5

Risk Factors for Androgenetic Alopecia

The most recent meta-analysis identified specific modifiable and non-modifiable risk factors 4:

Non-modifiable:

• Family history (OR 2.72 for presence, OR 4.24 for progression)
• Paternal family history (OR 2.22)

Modifiable:

• Smoking (OR 1.46 for presence, OR 1.60 for progression)
• Alcohol consumption (OR 1.72 for progression)
• Insufficient/poor quality sleep (OR 1.36 for progression)
• Overweight/obesity (OR 2.31 for progression)
• Insulin resistance and elevated fasting insulin
• Hypertension in men (OR 1.60)

Diagnostic Approach

Look for these specific clinical features:

1. Pattern and distribution of hair loss (diffuse vs. patchy vs. patterned)
2. Exclamation mark hairs at margins (suggests alopecia areata)
3. Scalp inflammation (suggests infection or scarring alopecia)
4. Broken hairs firmly anchored (suggests trichotillomania)
5. Temporal relationship to medications, illness, or stress

Dermoscopy is fundamental for all hair disorders and can distinguish between causes 5, 7. Yellow dots indicate active alopecia areata, while specific patterns help exclude trichotillomania and scarring conditions.

Investigations are unnecessary in most cases of typical male pattern baldness 5. Consider testing only when diagnosis is uncertain:

• Fungal culture for suspected tinea capitis
• Scalp biopsy for scarring alopecia or diagnostic uncertainty
• Serology for lupus or syphilis if clinically indicated

Common Pitfall: Do not routinely screen for iron deficiency in men with hair loss, as studies have not confirmed this association and no treatment response to iron replacement has been demonstrated 5.