Alopecia overview

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Ogechukwu Hannah Nnabude, MD

Overview

Alopecia is defined as loss of hair regardless of the cause. It can occur anywhere on the body. The hair cycle consists of three phases: anagen phase, which is the growth phase, catagen phase, which is the resting phase, and telogen phase, which is the shedding phase. This is the phase where hair falls out. Ninety percent of hair are in the anagen phase and the remaining ten percent are in the catagen and telogen phases. In the telogen phase, hair is going to recycle, and it starts growing again in the anagen phase.

Historical Perspectives

The use of the word alopecia stretches back to the era of the Greek physician Hippocrates. Minoxidil and finasteride are the only FA approved medications for treating alopecia. Hair transplant surgery originated in the 1900s and some of the major advancements in hair transplantation took place in Japan in the 1930s.

Classification

Alopecia is classified as either scarring or non-scarring. Over all, non-scarring alopecias tend to have better outcomes than scarring alopecias, which tend to be irreversible. The most common type is androgenetic alopecia. The majority of men start to lose hair in the third decade of life, while women begin to lose their hair in the fifth or sixth decade of life. As an individual ages, they will lose hair. Men more often lose hair in the front and the temporal regions of the scalp, while women tend to lose hair from the central area of the scalp. Also, female hair loss rarely results in complete baldness while male hair loss can end up with complete baldness. Males tend to retain hair at the posterior area of the scalp because the hair in this region is more resistant to the effects of androgenic hormones.

Pathophysiology

There are several pathophysiologic mechanisms responsible for alopecia, each related to the specific cause. For example, alopecia areata, is related with CD8+ T-cell autoimmunity, while androgenetic alopecia is related to the effects of androgen hormones hair follicles.

Causes

Scarring alopecia is caused by numerous dermatologic factors, including glabrous skin (non-hairy), and is very difficult to diagnose and manage. Non-scarring alopecia is characterized by the absence of visible inflammation of the skin involved. Medications, endocrine diseases, infectious diseases, and autoimmune diseases can also cause hair loss.

Treatment

Medical Therapy

In the USA, there are only 2 drug-based treatments that have been approved by the FDA (Food and Drug Administration) and one product that has been cleared by the FDA for the treatment of androgenetic alopecia, otherwise known as male or female pattern hair loss. The two FDA approved treatments are finasteride (marketed for hair loss as Propecia) and minoxidil.

Surgery

Surgery is another method of reversing hair loss and baldness, although it may be considered an extreme measure. The surgical methods used include hair transplantation, whereby hair-producing follicles are taken from the back and sides of the head and injected into bald or thinning areas.