Androgenetic Alopecia

Synonyms

Male pattern hair loss; common balding; male-pattern baldness; hormone-related alopecia; pelade.

Epidemiology

30-40% of women will have thinning hair by the age of 70 or older.
50-60% of men have a bald scalp by 70 years (but may start earlier, especially with a positive family history).

The condition is less commonly seen in men of East Asian ancestry.

Definition

Progressive androgen-dependent hair loss in typical locations associated with genetic predisposition and natural aging. In women, early aggressive disease or specific pattern (Hamilton-Norwood) of hair loss may indicate an endocrine disorder.

Aetiology & Pathogenesis

Polygenic inheritance. Abnormalities of local follicular androgen metabolism, especially increased activity of 5α-reductase, lead to increased levels of dihydrotestosterone.

Signs & Symptoms

Progressive and persistent asymptomatic hair loss in symmetrical pattern.

Localisation

Women - thinning of centro-parietal scalp, with widened parting but retained anterior hair line. The clinical pattern is variable and can be diffuse. Never complete hair loss on vertex.

Men - bi-temporal symmetrical regression, thinning of the vertex, later more complete loss leaving a residual parietal-occipital band.

Classification

Female pattern androgenetic alopecia: Ludwig scale I-III.
Male pattern androgenetic alopecia: Hamilton-Norwood scale (typical pattern; anterior pattern or vertex pattern) I-VII.

Laboratory & other workups

Usually not required. Consider endocrinologic evaluation in women with other signs of androgen excess (irregular menses, hirsutism, virilisation). Consider testing for concomitant causes of hair loss (e.g. low ferritin, thyroid dysfunction, lupus erythematosus etc).

Dermatopathology

Usually not required. Miniaturisation of the hair follicle with pseudohypertrophy of the associated sebaceous glands, increase in telogen hair follicles.

Course

Progressive but with highly variable course.

Complications

Chronic UV damage to the exposed scalp. Long-standing androgenetic alopecia can lead to micro-scarring. Psychosocial problems.

Diagnosis

Typical clinical findings. Consider a hair pull test and scalp dermoscopy. In women with early androgenetic alopecia, a trichogram (or automated videotrichogram) may be helpful. Excessive androgen production in women must be excluded by history and clinical findings; if other clues of androgen excess are present, endocrine evaluation needed.

Differential diagnosis

Other causes of hair loss e.g. diffuse alopecia areata or especially telogen effluvium in women, long-standing malnutrition with trace elements and vitamins.

Prevention & Therapy

Minoxidil 2 and 5% solutions, oral finasteride (strict avoidance of pregnancy in women of child-bearing years as finasteride is teratogenic), hair transplantation. Also oral contraceptives with anti-androgens in women. Consider wigs.

4.2.2 Androgenetic Alopecia