types of hair loss alopecia

Types of Hair Loss

Hair Today, Gone Tomorrow.

There are several types of hair loss, or, alopecia. Alopecia areata is an autoimmune condition in which the growth of hair follicles is shut down by the immune system. It usually occurs in random patches, typically on the scalp. It may be minor and limited to small areas, or it can be extensive. The follicles are not destroyed, and the hair may regrow again.

The most common type of hair loss is a genetic condition called androgenetic alopecia (AGA). It affects approximately 80 million people in the United States. It may affect women as well as men.

People Hair Loss Los Angeles CA everyday. This is a natural shedding process. Approximately 10-15% of the hairs on the scalp are shed daily. It is normal to shed 50-100 hairs per day. The follicles of the shedding hair remain dormant for 8 to 9 months, then, re-awaken and start to produce hair once again. The growth phase of a given follicle is about two years. Each day, as we shed these resting hairs (which usually have a small white bulb at one end), the hairs that were shed 8-9 months ago come back on line and start growing again. The comings and goings of the hairs thus remain in balance, and the net amount of hair on the head is stable. Under a variety of conditions, we may shed more than we replace at a given time. Factors such as stress (typically more than our usual stress), certain medications, recent surgery, general anesthesia, a traumatic injury, low iron, thyroid disease, and pregnancy (following a few months after deliver) may cause excessive shedding, known as telogen effluvium. One may shed 30-50% of ones hair before noticing that it is thinning. The majority of time, however, this situation is reversible over time, or if the underlying condition is corrected. It’s not what you shed, it’s what you keep that matters.

If there is progressive thinning of the hair over a 1-2 year period or longer, this may be a sign of androgenetic hair loss (AGA). Typically, AGA is characterized by certain patterns of hair loss. In men, there may be recession of the frontal hairline and/or thinning of the crown. Diffuse thinning on the top without recession may also occur. AGA in women is usually diffuse without recession, though frontal recession may occur.

AGA is an autosomal dominant trait with variable expression. It is not necessarily a gift from your maternal grandfather. Within a given family, there may be no hair loss seen in the parents, but some of their kids may have extensive early onset AGA, while other siblings maintain a full head of hair into late adulthood.

One may notice short hairs at the frontal hairline. Usually, these hairs are on the way out. The process of AGA is mediated by testosterone, in both sexes. Genetically programed hair follicles take up testosterone (T). In the follicle, T is converted to dihydotestosterone (DHT) by an enzyme called 5-alpha-reductase. DHT sends a chemical signal to the hair follicle, causing the follicle to miniaturize. As the follicle shrinks in size, the hair that it produces gets shorter, finer and thinner. Thus, the short hairs at the hairline. Eventually, the follicle scars down, and is out of game permanently. This process may take years for a given hair follicle.

Androgenetic alopecia is a progressive, unrelenting condition. It may appear as early as the teenage years. Its’ course may be slow or rapid. In later adulthood, there is also a progressive loss of follicles not related to DHT. This is part of the aging process. What a bummer!

In my next blog, I’ll discuss therapy.

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