Can hypogonadism (low testosterone) cause alopecia (hair loss) in men?

Low Testosterone and Hair Loss in Men

Low testosterone (hypogonadism) can cause decreased body and facial hair growth, but it typically does not cause male pattern baldness (androgenetic alopecia) on the scalp. 1

Relationship Between Testosterone and Hair Growth

Effects of Low Testosterone on Hair

• Low testosterone levels primarily lead to decreased body hair, including reduction in facial, pubic, chest, and axillary hair 1
• Hypogonadism affects secondary sex characteristics, which include the development of male hair distribution patterns 2, 3
• Signs of hypogonadism include decreases in body hair, along with other symptoms like decreased energy, libido, muscle mass, hot flashes, and gynecomastia 1

Androgenetic Alopecia vs. Hypogonadism

• Male pattern baldness (androgenetic alopecia) is primarily associated with dihydrotestosterone (DHT), which is converted from testosterone by the enzyme 5α-reductase 4
• Interestingly, men with premature balding often show lower (not higher) total testosterone levels compared to men without balding 5, 6
• The ratio of free testosterone to total testosterone may be more relevant to balding than absolute testosterone levels 6

Diagnosis of Hypogonadism

Clinical Assessment

• Consider testosterone assessment in men with:
  • Decreased body and facial hair
  • Reduced energy and libido
  • Decreased muscle mass
  • Erectile dysfunction
  • Hot flashes
  • Gynecomastia 1

Laboratory Testing

• Morning total testosterone level (drawn between 8-10 AM) is the initial test 1
• Normal testosterone range for adult men: 300-800 ng/dL 1
• If total testosterone is borderline low, check free testosterone level by equilibrium dialysis and sex hormone-binding globulin (SHBG) 1
• Further testing (LH, FSH) helps distinguish primary from secondary hypogonadism 1
• Repeat testing is recommended to confirm low levels 1

Treatment Implications

Testosterone Replacement Effects on Hair

• In men with confirmed symptomatic hypogonadism, testosterone replacement may improve body hair growth 1
• Effects on scalp hair are complex and testosterone replacement is not a treatment for male pattern baldness 1
• Testosterone replacement can improve other symptoms including sexual function, libido, well-being, muscle mass, and bone density 1

Treatment Options

• Transdermal preparations (gels, patches) provide stable day-to-day testosterone levels 1
• Injectable testosterone (e.g., testosterone cypionate) can be given at intervals of two to four weeks 3
• Implantable pellets provide longer-term treatment but require a procedure 1

Important Caveats

• Morning testing is essential as testosterone levels fluctuate throughout the day 1
• Obesity can confound testosterone assessment, as low total testosterone in obese men may be due to reduced SHBG rather than true hypogonadism 1
• Testosterone replacement in older men with hypogonadism has been associated with increased coronary artery plaque volume in some studies 1
• 5α-reductase inhibitors (finasteride, dutasteride) used to treat male pattern baldness can affect metabolic function and may contribute to erectile dysfunction 7

Clinical Bottom Line

When evaluating a man with hair loss, it's important to distinguish between:

1. Scalp hair loss (typically related to DHT and genetic factors, not low testosterone)
2. Body/facial hair loss (may be related to low testosterone)

If a patient presents with decreased body/facial hair along with other symptoms of hypogonadism, testosterone testing is warranted, but testosterone replacement should not be expected to reverse male pattern baldness on the scalp.