Hair Loss Overview
What is Hair Loss?
We are born with approximately 100,00 hair follicles on the scalp, and we shed 50-150 hair follicles each day as part of the normal hair growth cycle as hair follicles enter the telogen, or resting phase. This hair loss is typically replaced by the same number of hairs entering the hair follicle’s anagen or growth phase. Balding and thinning occur when this shedding occurs at a rate faster than regrowth. Depending on the cause, hair loss can be permanent or temporary. Alopecia, or hair loss, can affect any part of the body. It can affect just the scalp or any other body area with hair follicles. Hair loss is a common condition affecting millions of men and women and can cause considerable emotional distress.
Each hair on the scalp goes through a growth cycle. The majority of the follicles, about 90%, exist in the anagen (growth phase), which lasts 6 to 7 years, sometimes longer. A brief catagen (shedding) phase involves 1 to 3% of the follicles where hair begins to go through involution. Telogen, a dormant resting stage, follows this transitional catagen stage. The cycle repeats with telogen follicles again entering the anagen phase. This process is typically asynchronous; therefore, there are no appreciable changes in hair density with regular follicular growth cycles.
What are the Causes of Hair Loss?
Androgenic alopecia (AGA) is the most common cause of hair loss for both men and women. It is a hereditary condition determined by genes that make certain hair follicles susceptible to the effect of an androgen hormone called dihydrotestosterone (DHT). In AGA, DHT binds to receptors on sensitive hair follicles, activating genes that start the cascade of reactions that lead to progressively brief growth cycles causing the hairs to become shorter and thinner. This miniaturization continues until the follicle is incapable of sustaining healthy hair growth. AGA is estimated to cause hair loss in more than 90% of men and 50% of women. Nonetheless, many other causes of hair loss include autoimmune disorders (alopecia areata, cicatricial alopecia), certain medications (chemotherapy, high dose vitamin A, anabolic steroids), nutritional deficiencies (iron, zinc, B-complex vitamins), fungal scalp infections, chronic traction on the hair follicles (traction alopecia), severe emotional stress, acute medical illness and compulsive disorders (trichotillomania).
No matter the age or gender, it is essential to consult with a qualified hair loss physician to begin diagnosing and treating the problem.
