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Hair Loss Basics

Hair Loss Basics

Read about the basics of hair loss and hair growth. Here you will find more discussion on the science of hair loss, as well as the debunking of myths, the psychology of baldness, and even the fun side of hair.

Functions of Hair

The reasons we have hair, and the functions of its growth patterns, are not completely understood. Our prehistoric ancestors were much hairier than we are today; the reason for the decreased hairiness of modern man is unknown, although it is reasonable to assume that it parallels the use of clothing for warmth and protection from the sun and physical trauma.

Hair Anatomy

Each hair follicle measures about 3-4 mm in length and produces a hair shaft about 0.1 mm in width. The hair follicle has five main parts. Starting from the bottom of the follicle, they are; the dermal papillae, matrix, outer root sheath (ORS), inner root sheath (IRS), and the hair shaft.

Hair Growth Cycle

At any given time, about 90% of terminal hairs on one’s head are actively growing. This phase, called anagen, can last from 2 to 7 years, though the average is about three years. In catagen, which is the shortest phase lasting about 2-3 weeks, growth stops, the middle of the follicle constricts and the lower portion expands to form the “club.” The other remaining 10% of scalp hairs are in a resting state called telogen that, in a normal scalp, lasts about 3 to 4 months.

Hair Loss Myths

There is a sea of rumors floating out there that attempt to explain the “root” of the problem. After all, the great Hippocrates, father of modern medicine, thought that baldness could be cured by a mixture containing horseradish and pigeon droppings. The desire to have a simple solution – particularly one that is within our control – is understandable. But today, let’s debunk some of these hair loss myths and learn what the facts really are.

Hair Loss Glossary

What is Anagen effluvium? Densitometry? Traction Alopecia? Find out the definition of these and many other hair loss terms in our glossary.

Psychological Aspects of Balding

Hair loss is a problem for millions of men and women, both young and old. It can decrease self-esteem and confidence and limit the ability to enjoy life to the fullest. Balding affects people in different ways, but certain emotional reactions seem to be shared by many. Read on for a discussion on the psychology of baldness and balding.

Crazy Hair Dos

We have all noticed those crazy hairstyles that make you look twice — from far out colors to wacky cuts. These wild hair do’s (and don’ts) are probably some of the craziest hair styles you will see in your life.

Celebrity Hair Loss

Chat rooms are filled with speculation about the seeming rise and fall (and sometimes rise again) of follicles for such stars as Matt Lauer, Mel Gibson and Jude Law. And for sports figures like Tiger Woods and Pete Sampras. In the summary of an article in the Bergen Record, we see that such stars as Johnny Depp, Owen Wilson, and Matt Damon must increasingly depend upon their stylists to avoid bad hair days. Read this article on celebrity hair loss and how people in the public eye manage their hair loss.



What Is “Miniaturization”?

Miniaturization is the hormone-driven biological process in which hairs shrink in size over time, eventually leaving a bald scalp.

The hair follicle growth cycle consists of three phases: a growth phase (“anagen”), a transitional phase (“catagen”), and a resting phase (“telogen”). In genetically-susceptible hair follicles, a hormone called dihydrotestosterone (DHT) can cause the growth phase of the hair cycle to become progressively shorter. The individual hairs produced by these follicles are unable to grow to full size due to this shorter growth window and so they decrease in size (diameter and length) over time until they eventually disappear. This process of “miniaturization” is the main mechanism in androgenetic alopecia (genetic balding).

 Miniaturization: The Mechanism in Genetic Balding

Normal scalp hair grows in follicular units made up of one to four terminal (full thickness) hairs. The terminal hairs in any single DHT-susceptible follicular unit might be in varying stages of miniaturization, and thus be of varying diameters. When enough terminal hairs are in a state of miniaturization, there appears to be a visible thinning of the hair in the affected areas. As more hairs in each follicular unit become miniaturized, the process may lead to complete baldness in that area of the scalp.

DHT Resistance

In some areas of the scalp, most or all of the follicular units have the genetic predisposition to be immune to the effects of DHT. As a result, these areas might never become miniaturized, and so hair will remain on these parts of the scalp for the person’s entire life. This happens most often in the back and sides of the scalp, aptly known as the “permanent zone,” while the front and top of the scalp are the first areas to experience thinning and baldness.

 Normal scalp (left) scalp with miniaturization (right)

It is due to this genetic resistance to DHT in the permanent zone that hair transplant surgery can be an effective treatment for hair loss. In a hair transplant, follicular units are removed from the permanent areas of the scalp and implanted into balding areas. Because of a phenomenon known as “donor dominance” these transplanted follicular units retain their DHT-resistance even when transplanted into an area that was formerly populated by hair affected by genetic thinning. Once transplanted, the follicular units will continue to grow normal, non-miniaturized terminal hairs for the lifetime of the individual. Since hairs in the permanent zone provide the donor hairs for use in surgical hair restoration, this region of the scalp is also referred to as the donor area.

Miniaturization in the Donor Area

 A 32 year-old male patient showing diffuse hair loss (DUPA) including miniaturization in the donor area

Less commonly, some patients experience miniaturization in the donor area. When a patient’s donor area exhibits miniaturization, it decreases the chances they will be a candidate for a hair transplant. Transplanting hairs that could eventually become miniaturized and disappear negates the cosmetic purpose of a hair restoration procedure. Although miniaturization in the donor area is relatively uncommon in men, it is the norm in women who experience hair loss. This partly explains why fewer women are candidates for surgical hair restoration as compared to men. Only women who have a stable donor area are indicated for hair transplant surgery.

Miniaturization in the donor area is also a significant factor in determining the appropriate age at which a patient is a candidate for hair transplant surgery. In many patients with early hair loss, where extensive hair loss takes place when the patient is in their late teens or early/mid-twenties, it is difficult to impossible for the hair restoration physician to determine if the donor area is, in fact, going to be stable over time, or if it will eventually miniaturize. If a surgeon performs a hair transplant on a young patient whose donor area eventually experiences miniaturization, then the transplant may not have the desired cosmetic effect. Not only that, but the patient will be left with scarring in the donor area from donor hair harvesting without the cosmetic benefit of transplanted permanent hair. That is why at Bernstein Medical, we only recommend hair transplants in patients 25 years old or older.

Counter-acting the Effects of DHT

Since DHT is the main cause of male pattern baldness, why not develop a way to prevent DHT from causing miniaturization? That is exactly what happens with the medication Propecia (finasteride). It blocks the enzyme 5-alpha reductase Type II from converting the hormone testosterone into DHT. With lower levels of DHT in the bloodstream, fewer follicular units are exposed to the miniaturizing effects of DHT, and they continue to produce healthy, thick terminal hairs.

Rogaine, a topical over the counter medication for hair loss, also counter-acts the effects of DHT, but goes about it in a totally different way. DHT shortens the growth phase of the hair cycle, leading to progressively smaller and finer hairs. The active drug in Rogaine, called minoxidil, works by lengthening the growth phase of the hair cycle. The result is fewer follicular units that experience miniaturization.

Examples of Miniaturization

See below for three examples of different intensities of miniaturization: the permanent zone with little to no miniaturization, moderate miniaturization, and extensive miniaturization.

Example 1: The Permanent Zone

In the following patient, we see a close-up of the side of his scalp where the hair is not affected by DHT. We see mostly groups of full-thickness hairs (called terminal hairs) and a few scattered, fine vellous hairs, normally seen in a donor area. The pointer (left) indicates the location on the scalp in the close-up view.


Looking at the image above, you can see that the back and sides of the patient’s scalp (the “permanent zone”) have not succumbed to the effects of DHT due to follicles’ genetically-inherited resistance to DHT in that area of the scalp.

Example 2: Moderate Miniaturization

In the area of thinning (see circle below), we see that most of the hair has been miniaturized, although all of the hair is still present.


The hairs, while still present on the scalp, are so much finer in diameter than the patient’s original hair that they give the visual appearance of thinning.

Example 3: Extensive Miniaturization

In the region that is balding below (circle in the center of the scalp), there is extensive miniaturization and only very little loss of actual hairs. However, due to the dramatic thinning of the hair diameter, there is an appearance of almost complete balding in the area despite the presence of fine hair.


What these examples show is that, particularly in the early stages, the appearance of balding is due to the progressive decrease in hair shaft size caused by the miniaturizing effects of DHT, rather than the actual loss of hair.

This is the reason why hair loss medications, such as Propecia (finasteride) or Rogaine (minoxidil), which can reverse the miniaturization process, work well in early hair loss and why, with early hair loss, a surgical procedure is usually not necessary. If medications fail to restore enough hair, or if a patient chooses not to use medical therapy, then a hair transplant may be considered. Certainly, if an area is completely bald, medications will not re-grow hair and surgery can be considered as a first option.

Hair Loss Genetics


 An important androgen receptor gene is located on the X chromosome

There are many theories on the genetics of hair loss. You may have heard the popular myth that hair loss is passed down to men from the mother’s side of the family and to women from their father’s side. These myths travel alongside countless other genetic theories regarding how hair loss may be transmitted from one generation to the next.

While it is clear that hereditary male pattern baldness (androgenetic alopecia), is genetically-based and that common baldness cannot occur without the presence of specific inherited genes, we now know that these genes can be passed to offspring from either parent. What is still unclear is the exact mode of inheritance and the relative importance of each parent.

Many theoretical models have been proposed that focus on one particular dominant gene, but what is becoming apparent is that genetic hair loss is a polygenic trait. Hereditary hair loss is a complex genetic condition, most likely involving the expression of many different genes.

Historically, genetic engineering in hair loss took a single gene approach. This is where a single gene was examined in a specific group of people or families. Then another single gene would be examined in a specific group and so on. The myth that hair loss is passed down from a specific side of the family originated from a paper published in 1916 in which Dr. Dorothy Osborne stated that a specific pattern of baldness was inherited from only one specific parent. This theory has since been proven to be false. It is now known that genetic hair loss is a complex trait that may have contributing factors from both sides of the family. And because gene expression is related to a number of other factors (age, stress, hormone levels, etc.) simply inheriting the genes for baldness does not mean that the trait will manifest in such a way that it alters the person’s appearance.

  • Early Diagnosis – Identify those at high risk of becoming bald, before it is apparent clinically, so that hair loss can be treated in its earliest stages where medications have the greatest chance of being successful.
  • Gene Therapy – Fortunately, the scalp is readily accessible to topical therapies as it allows direct penetration of a drug to a target area. It is theoretically possible to introduce genetic material directly into cells using liposome-DNA mixtures that carry the missing gene(s) to generate new hair.

Please see our further resources on this complex but fascinating topic:

Hair Loss Myths


If have the suspicion that you are going bald, you probably want to know just what exactly is “happening under the hood.” Unfortunately, there is a sea of rumors that attempt to get to the “root” of the problem. After all, the great Hippocrates, father of modern medicine, thought that baldness could be cured by a mixture containing horseradish and pigeon droppings. The desire to have a simple solution within our control is understandable.

Take our quiz to see which hair loss myths are based in fact and which are not. Complete the quiz for details on each myth.

Hair loss is a problem for millions of men and women, both young and old. It can decrease self-esteem and confidence, and limit the ability to enjoy life to the fullest. Balding affects people in different ways, but certain emotional reactions seem to be shared by many.

Hair Loss and the Mating Game

The most common concern that people have when they begin to lose their hair is that they will be less attractive to the opposite sex. The interesting thing is that this is often only the view of the person that is balding and not that person’s partner. The spouse, or friend of those experiencing hair loss, commonly state that the only thing that bothers them is that it makes their partner depressed. The balding does not bother them per se.

It is interesting that women sometimes express that they want their spouses to look good for the wedding pictures, but once married, they become far less concerned. In fact, when a married man suddenly becomes interested in having a hair transplant, we have seen the spouse become suspicious of extra-marital interests and object to the procedure.

Balding on the Job

Another concern is that the person with hair loss feels he or she looks older than they actually are and will not be as competitive in the work force. Unfortunately, studies have shown that this is a real concern. When employers are screening job applicants, all other things being equal, those with hair are viewed more favorably than those who are bald.

Mirror Mirror on the Wall

People experiencing hair loss complain that the way they look does not fit with their own image of themselves. This occurs when someone begins to lose hair early i.e., in their late teens or twenties, but it is as much a problem when someone has had a full-head of hair for years (and is used to receiving compliments about their hair) and then their hair thins unexpectedly in middle age.

Hair loss is a universal marker for aging, with ones locks gradually diminishing over time. Your body slowly changes as well, with more sagging and wrinkles and ones muscle mass decreasing. However, hair loss can also occur suddenly at a young age, making you appear much older than you actually are.

Another aspect of balding is that people feel a loss of control. Hair is one of the few body parts that you can actually manipulate yourself. You can grow hair long, cut if off, you can wave it, dye it, or pull it back in a pony-tail. It serves as a form of self-expression. As people start to lose this form of self-expression, they can become depressed and withdrawn. But not everyone responds this way. People react very differently to their hair loss, with some considering it only a minor nuisance and others finding it so debilitating that they won’t be seen in public without their head covered.

So Did You Hear the One About…

One of the things that makes going bald difficult is that, for some reason, people feel that commenting or joking about hair loss is “fair game” when they wouldn’t dare mention that someone had bad skin, or had a limp. I often point out to patients, that just because people chose to comment about thinning hair, doesn’t mean they are judging that person or really care much about it. It just seems to be a socially acceptable thing to mention.

It’s Harder for Some Than For Others

Hair loss can be difficult for anyone, but there are a few psychological conditions that can make the situation even tougher. In particular depression, obsessive compulsive disorder (OCD), and body dysmorphic disease (BDD), can pose particular challenges in dealing with hair loss. For an overview on BDD see the slide show lecture by Dr. J. Thompson titled: Body Dysmorphic Disorder: Diagnosis and Management (powerpoint slide presentation).

He Thinks, She Thinks

Women seem to believe that female hair loss is less acceptable than hair loss in men. While this may be true, the vast majority of women have hair loss in a pattern that can be easily camouflaged. Women are often reassured when they realize that about 40% of women experience hair loss over their lifetime, but it is to such a small degree that it is rarely recognized by the opposite sex.

Mane Options

The important things to remember are that hair loss is very common, it is much more acceptable as one ages, and it is generally less important to other people than the person experiencing hair loss thinks. That said, it is not unreasonable to be upset about going bald. Fortunately, for those who are bothered by their hair loss, there are now excellent medications to prevent hair loss and excellent surgical treatments to restore hair once it is gone.

Hair Growth

The normal human scalp contains between 100,000 to 150,000 follicles that produce thick terminal hair. These hairs do not emerge individually from the scalp, but are arranged in small groups of 1 to 4 hairs each, called follicular units. There are approximately 50,000 to 65,000 follicular units on the human scalp. By comparison, the human body has approximately 5 million follicles that produce fine vellus hair.

At any given time, about 90% of terminal hairs on one’s head are actively growing. This phase, called the anagen phase, can last from 2 to 7 years, though the average is about three years. In the catagen phase, which is the shortest phase lasting about 2-3 weeks, growth stops, the middle of the follicle constricts and the lower portion expands to form the “club.” The other remaining 10% of scalp hairs are in a resting state called telogen that, in a normal scalp, lasts about 3 to 4 months.

When a hair enters its resting phase, growth stops, and the bulb detaches from the papilla, and the shaft is either pulled out (as when combing one’s hair) or pushed out when the new shaft starts to grow. When a hair is pulled out or falls out on its own, a small white swelling is found at the bottom of the hair shaft. Most people assume that this is the growth center of the hair, but it is just the clubbed, detached lower end of the hair shaft. The dermal papillae and the growth center of the hair remain in the scalp.

Scalp hair grows at a rate of about 0.44 mm/day (or 1/2 inch per month). Each hair follicle goes through the hair cycle 10-20 times in a lifetime.

Humans normally lose about 100 hairs per day. Everyone has a few hairs stuck to the comb each time they comb their hair. The presence of a large number of hairs on the comb, in the sink, or in the tub, can be a sign of hair loss caused by disease or medications. Common genetic balding, however, is not caused by excessive hair loss, but rather by the successive replacement of hair that is normally lost with smaller, finer hair – a process called “miniaturization.”

Hair Anatomy

Anatomically, hair is a distinct part of the skin referred to as an appendage. Other skin appendages include sweat glands, fingernails and toenails. Skin is composed of three main layers. The outer layer of skin is the epidermis. This layer is less than a millimeter in thickness and is composed of dead cells that are in a constant state of sloughing and replacement. As dead cells are lost, new ones from the growing layer below replace them.

Beneath the epidermis is the dermis, a tough layer of connective tissue (collagen) that is about 2 to 3 mm thick on the scalp. This layer gives the skin its strength, and contains both sebaceous glands and sweat glands.

Beneath the dermis is a layer of subcutaneous fat and connective tissue. The larger sensory nerve branches and the blood vessels that nourish the skin run deep in this layer. In the scalp, the lower portions of the hair follicles (the bulbs) are found in the upper part of this fatty layer.

An interesting characteristic of hair is that, in contrast to the commonly held notion that it grows as individual strands, it actually emerges from the scalp in groups of one to four (and sometimes even five or six). The reason for this is that hair follicles are not solitary structures, but are arranged in the skin in naturally occurring groups called follicular units. Although skin pathologists recognized this fact in the early 1980’s, its profound importance in hair transplantation was not appreciated until the mid-1990’s. The use of grafts composed of naturally occurring, individual follicular units, rather than an arbitrary number of hairs, has revolutionized hair transplant surgery.

Each hair follicle measures about 3-4 mm in length and produces a hair shaft about 0.1 mm in width. The hair follicle has five main parts. Starting from the bottom of the follicle, they are; the dermal papillae, matrix, outer root sheath (ORS), inner root sheath (IRS), and the hair shaft.

The dermal papillae contains specialized cells called fibroblasts that regulate the hair cycle and hair growth. The dermal papillae contains androgen receptors sensitive to DHT. For many years, scientists thought that hair growth originated from the dermal papillae. Recent evidence has shown that the growth center extends from the dermal papillae all the way up to the region of the follicle where the sebaceous glands are attached. It is now believed that the primary function of the dermal papillae is to regulate follicular growth and differentiation. If the dermal papillae is removed (this sometimes happens during a hair transplant), the hair follicle is often able to regenerate a new one, although the growth of the new hair will be delayed.

The matrix sits over the dermal papillae and contains actively dividing, immunologically privileged cells. Together, the dermal papillae and the matrix are referred to as the hair bulb. The size of the bulb and the number of matrix cells will determine the width of the fully-grown hair. The cells of the matrix differentiate into the three main components of the hair follicle: ORS, IRS and hair shaft.

The outer root sheath or trichelemma (Greek for coating sac), surrounds the hair follicle in the dermis and then blends into the epidermis on the surface of the skin, forming the structure commonly referred to as the pore (from which the hair emerges).

The inner root sheath essentially forms a mold for the developing hair shaft. It is composed of three parts (Henley layer, Huxley layer, and cuticle), with the cuticle being the innermost portion that touches the hair shaft. The cuticle of the IRS is formed by a layer of overlapping cells that interlock with the cuticle of the hair shaft. This overlapping mechanism holds the hair shaft securely in place, but also allows it to grow in length.

The cells of the IRS keratinize giving it rigidity and strength. Racial variations are felt to be due to the asymmetric formation of the IRS. If you look at the cross section of the IRS, the shape is oval in Europeans, flat in Africans, and round in Asians.

The hair shaft is the only part of the hair follicle to exit the epidermis (the surface of the skin). The hair shaft itself is also composed of three layers. The cuticle, the outer layer that interlocks with the internal root sheath, forms the surface of the hair and is what we see as the hair shaft emerges from the follicle. The middle layer, the cortex comprises the bulk of the hair shaft and is what gives hair its strength. It is composed of an organic protein called keratin, the same material that comprises rhinoceros horns and deer antlers. The center, or core, of the hair shaft, is the medulla, and is only present in terminal hair follicles.

Functions of Hair

The reasons we have hair, and the functions of its growth patterns, are not completely understood. Our pre-historic ancestors were much hairier than we are today; the reason for the decreased hairiness of modern man is unknown, although it is reasonable to assume that it parallels the use of clothing for warmth and protection from the sun and physical trauma. Hair serves as insulation from the cold; however, this does not explain why different human groups have distinct patterns of hair growth. Most people of Asian descent have very sparse body and facial hair, but some of these peoples such as the Inuit, Tibetans and Mongols people, inhabit some of the coldest regions on earth.

Hair has the additional function of extending the sensory capability of the skin beyond its surface. Although human hair lacks the wealth of sensory nerve fibers found at the root of whiskers of some animals, each hair has a nerve fiber going to the bulb of the hair follicle. Mechanical displacement of each hair causes a sensation that translates into an awareness movement on the skin’s surface. For example, when an ant or fly walks on one’s arm, one feels the displacement of hairs caused by the insect.

Hair also plays a role in the defense mechanisms of most fur-bearing animals. When an animal confronts a potential enemy, its fur bristles; standing on end to make the animal appear to be larger and more threatening. In dogs, this response is most visible in the neck area where the neck hairs, called hackles, rise. In cats, the most visible response is in the tail. An extreme example of the use of hair for self-defense occurs in porcupines: their quills, which are modified hairs, stand out from the body when the animal feels threatened. Porcupines have converted a reflex (that in most animals is purely defensive) into a formidable weapon. In modern man, with relatively sparse body hair, only vestigial traces of these reactions remain. A tiny muscle, called the erector pili, connects the lower portion of each hair shaft with the underside of the skin. When you are frightened, cold or angry, these small muscles contract, causing your hair to stand on end.

Each hair shaft also contains a small gland called the sebaceous gland, located next to the hair shaft. Sebaceous glands make a yellow, fatty substance called sebum that lubricates the hair. Each time the erector pili muscle contracts, the gland is squeezed, and a small amount of lubricant is applied to the surface of the hair.

Hair, along with skin pigmentation, is the major natural protection that we have against the sun’s harmful ultra-violet rays. Scalp hair also plays an important role in preventing mechanical trauma to the skull. Hair acts as a “dry lubricant” in areas that rub, such as under the arms and in the groin, and serves to disperse pheromones (body secretions that are involved in sexual attraction).

Hair is integral to our body image and can have a profound influence on our self-esteem and self-confidence. There is no other part of the human anatomy that can be changed or manipulated so easily. Hair can be groomed, styled, waved, straightened, dyed, braided, or cut, and, unlike tattoos or body piercing, changes made to our hair can be completely reversed. Hair serves as an important means of self-expression, and the loss of this form of self-expression in those going bald may account, at least in part, for the despair that they may experience.

Hair Loss Glossary

Acne Keloidalis
Firm, red brown papules (small bumps) and plaques on the back of the scalp at the nape of the neck of unknown etiology. It has a genetic predisposition and occurs more commonly in persons of African descent. It is treated with local injections of corticosteroids, antibiotics, and surgery. Because these lesions occur in the donor area, its presence is a relative contraindication for hair restoration surgery.

The medical term for hair loss of any type. It can result from illness, functional disorder, or a hereditary predisposition.

Alopecia Areata
An autoimmune condition where the body produces antibodies against its own hair follicles. It is characterized by the sudden appearance of smooth circular patches of bald spots on the scalp, beard, eyelashes, or other parts of the body. Hair transplantation is generally not indicated for this condition and treatment consists of injections with cortisone or other medical therapies. Generally the earlier the onset and the more extensive the hair loss, the worse the prognosis. Other characteristic features include: 1) exclamation point hairs – hairs tapered at the bottom due to the inflammation which causes injury to the hair shaft, 2) hair pigment changes, 3) grid-like nail pitting, 4) positive hair pull test – showing telogen hairs and hairs with tapered broken ends (dystrophic anagen hairs).

Alopecia Marginalis
Hair loss primarily at the hairline and temples which is usually caused by continued traction from braids or hair extensions. If condition persists over a length of time, hair loss may become permanent even when braiding is discontinued. Other causes of hair loss in men occurring in this distribution include a hereditary thinning in the area (unrelated to trauma) and follicular degeneration syndrome.

Alopecia Totalis
A type of alopecia areata that results in the total loss of hair on the scalp.

Alopecia Universalis
A type of alopeica areata that involves all the hair on the body including the eyelashes, eyebrows, and hair on the trunk and extremities.

The growing phase of the hair follicle. It generally lasts from 2 to 5 years.

Anagen Effluvium
Extensive hair shedding that results from damage to the hair follicles. It appears soon after exposure to the offending agent. One can see broken hair shafts and tapered, irregular hair roots. Anagen effluvium is seen with chemotherapy and radiation therapy.

Androgenetic Alopecia
Hair loss resulting from a genetic predisposition of follicles to the affects of DHT. It is characterized the replacement of thick terminal hairs with fine, miniaturized hairs that are eventually lost. Also termed female pattern baldness, male pattern baldness, hereditary alopecia and simply common baldness.

The intermittent stage between the growing (anagen) and resting (telogen) phases of the hair growth cycle. In this transitional phase, the follicle stops producing hair and the base of the hair follicle begins to move upwards through the dermis. This phase typically lasts 2-4 weeks.

Chronic Telogen Effluvium (CTE)
CTE is marked by increased shedding of telogen hairs and diffuse thinning especially at the temples. It affects women age 30-60 and can start abruptly with, or without, an initiating factor. It usually does not lead to complete baldness and can resolve in 6 months to 6 years. It typically has a long, fluctuating course with patients losing up to 50-400 hairs/day. Patients with CTE complain of excessive hair shedding whereas those with androgenetic alopecia complain of gradual thinning. The mechanism of CTE is felt to be a shorted anagen (growth) cycle. Unlike androgenetic alopecia, chronic telogen effluvium is not characterized by miniaturized hair follicles. Hair transplants are not indicated in CTE as the hair loss tends to be diffuse and patients should get better over time without treatment.

The number of hairs in a specific area. The average hair density on the scalp is 2.25 hairs/cm

Densitometry is a technique to help evaluate a patient’s candidacy for hair transplantation and predict future hair loss. It analyzes the scalp under high-power magnification to give information on hair density, follicular unit composition and degree of miniaturization.

Diffuse Patterned Alopecia (DPA)
Diffuse Patterned Alopecia (DPA) is a type of androgenetic hair loss characterized by diffuse thinning in the front, top, and vertex of the scalp. It is usually associated with a stable permanent zone.

Diffuse Unpatterned Alopecia (DUPA)
A type of androgenetic hair loss that occurs over the entire scalp so that there is no permanent zone of hair normally present in the back and sides of the scalp. The progression of hair loss is often rapid and can result in an almost transparent look due to the low density. Diagnosing DUPA is imperative, as most patients with diffuse unpatterned alopecia should not have a surgical hair restoration, as the transplanted hair will not be permanent. DUPA is a pattern more commonly seen in women. The use of densitometry is very helpful in diagnosing this condition.

Dihydrotestosterone (DHT)
DHT is a male hormone that is suggested to be the main cause for the miniaturization of the hair follicle and for hair loss. DHT is formed when the male hormone testosterone interacts with the enzyme 5-alpha reductase.

Discoid Lupus Erythematosus (DLE)
An auto-immune disease characterized by scaly red plaques with telangiectasia (fine blood vessels), plugged follicles, atrophy (thinning of the skin) and pigmentary changes. DLE often leads to local areas of scarring and permanent localized hair loss.

Treatment includes topical corticosteroids, intra-lesional corticosteroids, systemic corticosteroids, anti-malarials, topical tacrolimus topical tazarotene, topical imiquimod, isotretinoin and thalidomide. Surgical hair restoration is generally not indicated in DLE since the disease process had the propensity to recur. DLE may or may not be associated with the more generalized disease SLE.

Female Pattern Alopecia
Female pattern hair loss is characterized by a gradual thinning of the front and/or top of the scalp with relative preservation of the frontal hairline. Although the areas on the top of the scalp are affected the most, the process tends to be diffuse involving the entire scalp to some degree. In female alopecia, the genetics seem to be more complicated than a simple response to androgens. Women with female alopecia are candidates for hair transplantation only if the back and sides of the scalp are stable.

Follicular Degeneration Syndrome
A form of scarring alopecia caused by the premature shedding of the inner root sheath of the hair follicle. It eventually results in complete follicular destruction. Because it occurs in a band around the frontal part of the scalp it had been felt that the condition was due to traction. It is now felt that the condition is idiopathic and unrelated to mechanical trauma or that it can be caused by a hot comb.

Folliculitis Decalvans
A form of scarring alopecia characterized by redness, swelling and pustules around the hair follicle, leading to the destruction of the follicle and consequent permanent hair loss. Folliculitis decalvans affects both men and women and may start first during adolescence or at any time in adult life. The exact cause is unknown. In most cases Staph aureus can be isolated from the pustules but the role of the bacteria is not clear.

Treatment includes: oral antibiotics – cephalosporin, minocycline, rifampin, or intralesional corticosteroids

Frontal Fibrosing Alopecia
More common in post-menopausal women, the front part of the scalp appears shiny, smooth and devoid of hair follicles. This pattern can mimic androgenetic alopecia but, on close inspection one notes scarring and the absence of hair follicle openings.

There may be signs of inflammation including redness and scaling. The condition may be a variant of Lichen Planopilaris.

Lichen Planopilaris (LPP)
A condition affecting the hair follicles in localized scaly red patches that result in scarring and hair loss in the affected areas. The disease is characterized by a band-like layer of inflammatory cells at the upper most layer of the dermis that damages the hair follicles.

Treatment includes: potent topical corticosteroids, intra-lesional corticosteroids, systemic corticosteroids, oral retinoids, anti-malarials, and oral cyclosporine

Loose Anagen Hair Syndrome
This is a very rare condition but seen more often in females than males, presenting early in childhood, usually between the ages of 2 and 9 as diffuse patches of hair loss. This syndrome is characterized by a defective inner root sheath (abnormal keratinization) that prevents it from grasping the hair shaft cuticle. As a result the newly growing hair shaft falls out. The hair is usually blonde, feels matted or sticky, lusterless and does not require cutting. A hair-pull test is positive for anagen hairs. No systemic abnormality is associated with it. With adolescence the hair grows longer, denser and darker, but the hair pull remains positive.

Ludwig Classification
Classification of female pattern hair loss. It encompasses three stages: Mild (type 1), Moderate (type II) and Extensive (type III). In all three stages, there is loss on the front and top of the scalp with preservation of the frontal hairline. If the person’s donor hair is stable at the back and sides of the scalp, women of all three types of Ludwig Classification may be candidates for hair transplantation.

Male Pattern Baldness (MPD)
Also known as androgenetic alopecia or common baldness. This is the most common type of hair loss, caused by the affects of DHT on susceptible hair follicles. It mainly affects the frontal, top and crown of the scalp and can result in a pronounced horseshoe pattern.

Marginal Hair Loss (see Alopecia Marginalis)

Norwood Classification
Published by Dr. O’tar Norwood in 1975, this is the most common classification for describing genetic hair loss in men. The regular Norwood pattern has seven stages that begin with recession at the temples and thinning in the crown. The Norwood Class A pattern has five stages and is characterized by a predominantly front to back progression of hair loss.

Pseudo Palade of Braque
A non-specific scarring alopecia of unknown cause. It also may represent the end stage of other inflammatory scalp conditions. It presents with white or flesh-colored atrophic plaques, without active inflammation.

Systemic Lupus Erythematosis (SLE)
An auto-immune disease where the immune system attacks the body’s own cells, resulting in inflammation and tissue destruction. SLE can affect any part of the body, but most commonly affects the skin, joints, kidneys, heart and blood vessels. The course of the disease is unpredictable, with periods of flares and remissions. Lupus can occur at any age and is more common in women. The skin manifestations are quite varied and can present with localized lesions (DLE), diffuse hair loss and sensitivity to the sun. The name comes from the fact that the photo-sensitive rash that occurs on the face resembles that of a wolf.

The resting phase (2-4 months). In this period a new hair begins to grow and the old hair is gradually forced out of the follicle and shed.

Telogen Effluvium
This condition has its onset 2-3 months after stress or insult to the scalp. Generally 35-50% of hair is affected. One can see over 300 hairs shed per day. The hairs are characteristically “club” hairs, i.e. telogen hairs that have a small bulb at the end. Telogen effluvium is much more common in women than men.

Tinea Capitis
A fungal infection of the hair follicles of the scalp characterized by the formation of small crusts at the base of the follicles. It is also referred to as ringworm of the scalp. It can result in small patches of permanent hair loss. It can be diagnosed by a scalp scraping and a hair pull tested for fungus on a KOH prep and a fungal culture. The most common organism producing this condition is Tinea Tonsurans.

Triangular Alopecia
A triangular shaped area devoid of hair that most commonly occurs in the temples. The apex of the triangle often points towards the vertex of the scalp. It can be unilateral or bilateral. Fine, vellus hairs can be seen in the bald patch. The condition appears at birth or in early childhood and is stable. The early, stable appearance, fine vellus hair and characteristic location, help to differentiate it from alopecia areata. Hair transplantation is the treatment of choice.

Traction Alopecia
Develops from continuous traction or pulling on the hair. The hair loss is most prominent at the frontal hairline and temples. It can be seen with hair systems and corn-row hair styles. It is common in African-Americans that braid or corn-row their hair. When long-standing, the hair loss can be permanent

A compulsive disorder characterized by pulling of one’s hair. The most common area is scalp hair causing patchy areas of hair loss with broken hairs of varying lengths. Most commonly seen in females ages 6 to 30. This condition can also involve the eyebrows or upper eyelashes (upper lashes are easier to grab). The diagnosis can be made by cutting or shaving the hair so that it is too short to grab and then observing the growth. Patients suspected of having trichotillomania should be sent for a psychiatric evaluation. A hair transplant is not indicated.

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