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Hair Loss Causes in Men and Women

Determining the Cause

As I began to rapidly lose my hair in my early twenties, I had a strong feeling that if I did not find a way to reverse my hair loss soon, I would be a Norwood 6 or 7 by the time I was 30 years old. The thought of being nearly bald and possibly looking almost 10 years older than my actual age while still relatively young created a knot in my stomach, and it was at that moment that I resolved to determine exactly what was causing my hair loss. It was only after figuring out why I was losing my hair, I reasoned, would I have any hope of growing it back.

Early into my research, I found a lot of information about the causes of hair loss from a number of excellent sources (e.g. biology textbooks, literature from medical organizations). I was, however, not content with relying solely on the information available in textbooks and the reference material put out by medical organizations to learn about what exactly causes hair loss; I was afraid that if I did not conduct more comprehensive research, I might miss some of the contributing factors of hair loss that specifically pertained to me. Some of the other sources that I consulted with, in order to leave no stone unturned, included: magazine articles, television news segments and information available on the internet.

After carefully going over all the information that I found from a cross-section of well-respected sources, I was able to ascertain that while there are a myriad of factors that work in conjunction with each other to cause an individual to lose his or her hair, there are several factors that are primarily responsible for causing an individual’s hair loss. These factors can be divided into two categories: (1) genetic and (2) environmental.

Before going into a more in-depth discussion on the main causes of hair loss, I wanted to provide a brief description of the hair growth cycle and a biological explanation of hair loss because I have found that when people are suffering from a particular condition or disease (hair loss is considered either one), they appreciate having additional knowledge or perspective about it.

 Stages of Hair Growth

Anagen: This is the growth phase of the hair growth cycle, and it lasts anywhere from 2-6 years. Approximately 85% of all hairs on the scalp are in the anagen phase at any given time. During anagen, the dermal papilla, which is composed of a small cluster of a few hundred specialized fibroblast cells and can be thought of as a nipple-like protrusion from the dermis layer of the skin, attaches to the hair bulb (the bottommost part of the hair follicle) and provides it with the nutrients (i.e. glucose, amino acids) that are necessary in order to promote hair growth. Hair grows at an average rate of a 1/2 inch per month (6 inches a year) during the anagen phase.

Catagen: This is the transitional phase of the hair growth cycle, and it lasts about 2-3 weeks. Approximately 2-3% of all hairs on the scalp are in the catagen phase at any given time. During catagen, the hair follicle shrinks to 1/6 of its normal length. The lower part of the follicle is destroyed, and the dermal papilla breaks away from it to rest below the scalp. Having had its supply of nutrients, thus, effectively cut off from it, the hair follicle continues to disintegrate and the hair shaft located within it is pushed upward towards the surface of the skin. The catagen phase can best be thought of as the time when the hair ceases to grow but does not actually fall out.

Telogen: This is the resting phase of the hair growth cycle, and it lasts about 3 months. Approximately 10-15% of all hairs on the scalp are in the telogen phase at any given time. During telogen, the last remaining cells of the hair follicle aggregate at the root of the hair to form what is known as a “club hair.” After the formation of the club hair (which is characterized by a solid, white bulbous enlargement at the root), the hair follicle is considered to be completely at rest and the hair shaft completely formed. The hair shaft will then fall from the scalp after receiving a “final push” from everyday activities such as shampooing or towel drying one’s hair.

Hairs in the telogen phase that have not been shed in the above manner will be dislodged from their respective hair follicles when the hair bulb reattaches to the dermal papilla, a new anagen phase commences and a nascent hair nudges the old one out of the follicle.

How Hair Is Lost


Hair loss can best be defined as a decrease in the percentage of hair follicles on an individual’s scalp in the anagen phase with a corresponding increase in the percentage of hair follicles in the telogen phase.

There are, however, two primary but distinct ways by which the hair follicles arrive at this same end result. One of them is through a condition known as androgenetic alopecia and the other is through a condition known as telogen effluvium.

In the former condition, hairs on the scalp that are in the anagen phase of the hair growth cycle become progressively thinner and shorter as the lengths of the growth phases that they are in decrease (a process known as miniaturization) with each successive hair cycle that they go through until the follicles that they reside in eventually become dormant.

Hair follicles that have reached the telogen phase in this manner are mostly influenced by genetic factors (i.e. hormones), and are typically located at the hairline and crown areas of the scalp. It is also important to note that hair loss caused by androgenetic alopecia is characterized by the visible loss of hair.

In the latter condition, after hair follicles on the scalp have entered the telogen phase as a normal part of the hair growth cycle, instead of returning to the anagen phase after a period of about 3 months, some of the follicles remain in resting mode for a prolonged period of time. This type of hair loss, similar to androgenetic alopecia, mostly occurs on a gradual basis, and not as a result of an increase in the rate at which hair follicles enter the telogen phase and remain there.

Hair follicles that have reached the telogen phase in this manner are mostly influenced by environmental factors (e.g. diet, stress), and are typically located on the top of the scalp and to a lesser extent at the back and sides of the scalp. It is also important to note that hair loss caused by telogen effluvium is characterized by thinning hair.

If a young man, for instance, over a period of 2-3 years, develops visible temporal recession and slight thinning on the top of his scalp, it would be fair to say that his hair loss is the result of both genetic and environmental factors.

Top Hair Loss Factors

Genetics play a significant role in contributing to an individual’s hair loss, and for the most part are hard to influence. The reason for this is, the dermal papilla contains a genetically predetermined number of androgen receptors that make it possible for dihydrotestosterone (DHT) (which is a powerful chemical derivative of the hormone testosterone that is produced when the latter is metabolized by the enzyme 5-alpha reductase) to bind to it.

As more and more of the androgen receptors on the dermal papilla become clogged with DHT, the dermal papilla becomes progressively smaller, and the supply of nutrients to the particular hair follicle that it is supporting gradually decreases. This phenomenon begins the miniaturization process, and it continues until the hair follicle reaches a state of dormancy and ceases to produce any hair. Some key genetic factors to note:

  • Build-up of DHT on the scalp over time. After a young man or woman enters puberty, there is a marked increase (especially in men) in the amount of testosterone that is produced by his or her body. This testosterone, which freely circulates in the bloodstream, and is increased by the consumption of animal fat (e.g. red meat, regular milk), is converted into DHT by 5-alpha reductase residing in the dermal papillae. Miniaturization then ensues and after prolonged exposure to DHT, hairs eventually stop emerging from areas of the scalp (i.e. hairline, crown) that contain a high concentration of androgen receptors.
  • Decreased estrogen production after reaching menopause. In women, the hormone estrogen counteracts the testosterone that is produced by their bodies and, as a result, there is only a small amount of the latter readily available in their bloodstreams that can be converted into DHT. After menopause, however, there is a dramatic decrease in the amount of estrogen that a woman produces and, consequently, a large increase in the amount of DHT available to clog the androgen receptors on the dermal papillae residing just below her scalp. The miniaturization process then commences, with a woman often finding herself experiencing a substantially greater degree of hair loss (usually in the form of a general diffuse thinning all over the scalp) from her 50s onward than when she was 25 years old.
  • Return to normal estrogen levels after pregnancy. When a woman becomes pregnant, there is a significant increase in the amount of estrogen (which promotes the growth of scalp hair) that is produced by her body. The surge in estrogen production, in turn, causes virtually all the hairs on a woman’s scalp to become locked into the anagen phase and, as a result, an expectant mother generally experiences only minimal hair loss throughout the course of her pregnancy. After giving birth, however, the elevated estrogen levels soon return to normal, and almost all the hairs that were at rest pre-pregnancy simultaneously re-enter the telogen phase, before falling from the scalp in a massive shedding that takes place approximately 3-4 months later. Post-partum hair loss can best be thought of as a self-correcting mechanism that brings the percentage of hairs on a woman’s scalp in the growth and resting phases back inline with the norms of the hair growth cycle, and not a net loss of hair.

When it comes to the environmental factors of hair loss, I have found that, more often than not, hair loss sufferers largely underestimate the amount of power that they have in their own hands to influence them.

By eating well and exercising, for instance, two of the more common causes of hair loss, an unhealthy diet and a carefree lifestyle, can be mitigated to a large extent, and incidents of cancer (and chemotherapy treatments), which are often caused by poor diet and/or lifestyle choices, can also be greatly reduced. Some important points to be mindful of:

  • Having a diet largely composed of highly-processed foods. With breakfast often being a bagel in the office laden with cream cheese, and lunch and dinner consisting of highly-processed fast food meals, it is difficult for the body to receive the proper amounts of all the nutrients that are necessary in order for it to perform the vast array of functions that will safeguard the longevity of an individual’s life. Since having hair on the scalp, however, is not considered by the body as being essential for survival, it then begins to gradually shift many of the hair follicles that are located on its pate into an extended resting phase (telogen effluvium) over time. This move helps to ensure that some of the same nutrients (e.g. protein, iron) or resources that are required to grow hair are available in adequate supply to the organs (e.g. heart, liver) in the body whose proper functioning the body considers critical for its continued existence. Until eating a well-balanced diet becomes the norm (and the body no longer has to devote almost its entire cache of nutrients to carrying out life-sustaining functions), the hair loss that a man or woman is suffering from is going to remain.
  • Constriction of blood vessels in the scalp due to high stress levels. Between the pressures of working your way up the corporate ladder, raising a family and maintaining friendships outside of the office, stress is going to be a part of your everyday life. This stress, in turn, constricts the blood vessels in the scalp, decreases blood circulation to that region and prevents the hair follicles from receiving many of the nutrients that are vital for promoting healthy hair growth. A slow but steady rate of hair loss then develops on the scalp (particularly at the top), often adding to the various pressures that an individual may already be dealing with. By setting clear but attainable career goals, exercising on a regular basis and getting a good night’s sleep, however, I have found that stress levels can be kept at a minimum.
  • Falling of hair from the scalp as a side effect of chemotherapy. Individuals who have been diagnosed with cancer often begin chemotherapy treatments in order to eradicate the malignant tumor cells residing within their bodies. The chemotherapy medication, however, which is designed to attack rapidly dividing cell populations found in the body, does not distinguish between the quickly proliferating but harmful cancer cells (wherever they might be situated) and the swiftly replicating but healthy hair cells located in the bulb of hair follicles that are in the anagen phase of the hair growth cycle. As a result of the drugs’ inability to focus solely on destroying the cancerous cells, the hairs on the scalp in the growth phase (which can be up to 85%) of cancer patients undergoing chemotherapy become weak and brittle, and about 2-3 weeks after the first treatment has occurred, will begin to fall from the scalp in large clumps (a condition known as anagen effluvium). It is also important to remember that hair loss caused by chemotherapy medication is not permanent. Approximately 3-4 months after an individual’s last chemotherapy session has taken place, new hairs will start to sprout from his or her scalp.

Misconceptions About Hair Loss