Androgenetic alopecia (pattern hair loss)

Androgenetic alopecia, known as pattern hair loss or common baldness, is the most frequent cause of hair loss in both men and women. It is hereditary and progressive: hair in certain areas becomes finer and shorter until it stops growing. It affects most men during their lifetime and a significant proportion of women, especially after menopause.

What androgenetic alopecia is

Androgenetic alopecia is caused by the action of dihydrotestosterone (DHT), a hormone derived from testosterone, on genetically sensitive hair follicles. DHT makes the follicle miniaturise: each cycle produces a finer, shorter and less pigmented hair, until the follicle no longer produces visible hair.

How androgenetic alopecia shows

• In men, androgenetic alopecia starts with a receding hairline at the temples and thinning at the crown, which can eventually merge. It is graded with the Hamilton-Norwood scale, from I to VII.
• In women, androgenetic alopecia usually spares the front hairline and causes diffuse thinning on top of the head, with a widening parting. It is graded with the Ludwig scale.

Diagnosis of androgenetic alopecia

A dermatologist diagnoses androgenetic alopecia by examining the scalp and using trichoscopy, which shows hair miniaturisation. In women with irregular periods, acne or excess body hair, hormones are tested. Other causes of hair loss should be ruled out, such as telogen effluvium (temporary shedding after stress, dieting, childbirth or illness), iron deficiency or thyroid problems.

Treatment of androgenetic alopecia

Androgenetic alopecia cannot be cured, but it can be slowed and partly reversed if treated early:

• Minoxidil, topical or oral (prescribed by a doctor): prolongs the hair growth phase. Useful in men and women.
• Finasteride and dutasteride: block DHT production. They are the standard treatment in men; in women they are used only in specific cases.
• Scalp mesotherapy and platelet-rich plasma (PRP): complementary treatments with moderate evidence.
• Hair transplant: moves follicles from the back of the head, which are resistant to DHT, to bald areas. It is the only way to regain hair where follicles have disappeared, and medical treatment is still needed to keep the native hair.

Medical treatments take six to twelve months to show results, and if they are stopped, hair loss resumes.