Dermatology · Hair Disorders
The facts most likely to be tested
Androgenetic alopecia is a genetically determined condition characterized by progressive hair follicle miniaturization mediated by dihydrotestosterone (DHT).
The primary pathophysiology involves the conversion of testosterone to DHT by the enzyme 5-alpha-reductase within the dermal papilla.
Clinical presentation in males typically involves bitemporal recession and vertex thinning, while females present with diffuse thinning of the crown with preservation of the frontal hairline.
Minoxidil is the first-line topical therapy that acts as a potassium channel opener to prolong the anagen phase of the hair cycle.
Finasteride is the first-line oral therapy for males that functions as a Type II 5-alpha-reductase inhibitor to decrease serum and scalp DHT levels.
Diagnosis is primarily clinical, based on the characteristic pattern of hair loss and the absence of scalp inflammation or scarring.
Spironolactone is an off-label androgen receptor antagonist often utilized as a second-line treatment for androgenetic alopecia in females.
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A 28-year-old male presents to the clinic complaining of a receding hairline. He reports that his father and maternal grandfather both experienced significant hair loss at a young age. On physical examination, there is bitemporal recession and thinning at the vertex of the scalp. The scalp skin appears normal with no evidence of inflammation, scaling, or scarring. A pull test is negative.
What is the most appropriate pharmacologic intervention to halt the progression of this patient's condition?
Finasteride
The patient's presentation is classic for androgenetic alopecia, and finasteride is the gold-standard oral therapy that inhibits 5-alpha-reductase to prevent further follicle miniaturization.
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Etiology / Epidemiology
Genetically determined androgen-dependent hair loss; affects up to 50% of men by age 50.
Clinical Manifestations
Progressive miniaturization of hair follicles; bitemporal recession in men, vertex thinning in women.
Diagnosis
Primarily clinical diagnosis; trichoscopy reveals hair shaft diameter diversity.
Treatment
Minoxidil (topical) and Finasteride (oral) are first-line; teratogenic in pregnancy.
Prognosis
Chronic, progressive condition; lifelong therapy required to maintain results.
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Epidemiology & Etiology
Most common cause of hair loss worldwide, driven by polygenic inheritance and androgen sensitivity. Prevalence increases significantly with age in both sexes. It is a hormone-dependent process involving the conversion of terminal hairs to vellus hairs.
Pertinent Anatomy
Affects the scalp follicles specifically, sparing the occipital and temporal fringes. The process involves the follicular unit undergoing progressive atrophy and shortening of the anagen phase.
Pathophysiology
Increased sensitivity to dihydrotestosterone (DHT) leads to progressive miniaturization of hair follicles. The enzyme 5-alpha-reductase converts testosterone to the more potent DHT. This shortens the anagen (growth) phase while lengthening the telogen (resting) phase, resulting in thinner, shorter, and less pigmented hair.
Clinical Manifestations
Men typically present with Hamilton-Norwood pattern: bitemporal recession and vertex thinning. Women present with Ludwig pattern: diffuse central thinning with preservation of the frontal hairline. Red flags include rapid onset, patchy loss, or scaling, which suggest alopecia areata or tinea capitis.
Diagnosis
Diagnosis is clinical based on pattern and history. Trichoscopy is the gold standard for confirming miniaturization, defined as >20% variation in hair shaft diameter. Laboratory testing (e.g., DHEAS, testosterone) is only indicated if signs of hyperandrogenism (hirsutism, irregular menses) are present.
Treatment
Topical Minoxidil (2% or 5%) is the first-line treatment for both sexes. Oral Finasteride (5-alpha-reductase inhibitor) is indicated for men; teratogenic and contraindicated in women of childbearing age. Hair transplantation is a surgical option for refractory cases.
Prognosis
Condition is progressive without intervention. Treatment must be continued indefinitely; cessation leads to loss of gains within 6-12 months. Psychosocial distress is the most common complication.
Differential Diagnosis
Alopecia areata: well-demarcated, smooth, round patches
Telogen effluvium: diffuse shedding triggered by stress/illness
Tinea capitis: scaling, erythema, and lymphadenopathy
Trichotillomania: broken hairs of varying lengths, irregular borders
Anagen effluvium: abrupt, diffuse loss following chemotherapy