Chapter 3:   Causes of Hair Loss
 

Most people who are losing their hair are losing it simply because they have inherited a genetic design that pre-disposes them for baldness. Hair loss can also be caused by underlying medical problems, drugs, infections and a variety of other factors. Medical problems that can cause diffuse hair loss include: anemia, thyroid disease, connective tissue diseases (such as Lupus), severe nutritional deficiencies, surgical procedures, general anesthesia, and severe emotional problems. In women, obstetric and gynecologic conditions, such as post-partum and post-menopausal states, and ovarian tumors can cause hair loss.

A relatively large number of drugs can cause a temporary form of hair loss called “telogen effluvium,” a condition where hair is shifted from its growth phase into a resting stage and then, after several months, is shed. Fortunately, this shedding is reversible when the medication is stopped.  Drugs that can cause diffuse hair loss include; blood thinners (anti-coagulants), medication for seizures, gout, high blood pressure, and thyroid disease, anti-inflammatory drugs such as prednisone, medications that lower cholesterol and other lipids, mood altering drugs, chemotherapy, oral contraceptive agents (particularly those high in progestins), diet pills, high doses of Vitamin A, and certain street drugs (such as anabolic steroids and cocaine).       

Although there are a number of dermatologic conditions that cause hair loss, they produce a pattern that is different from that of common baldness (androgenetic alopecia) or the diffuse forms of hair loss mentioned above. Localized hair loss may be sub-divided into scarring and non-scarring types.

Alopecia Areata is a genetic, auto-immune disease that typifies the non-scarring type. It manifests with the sudden onset of discrete round patches of hair loss (although the condition can become generalized). In its mild form, it can be treated with local injections of steroids.  Traction Alopecia, the hair loss that occurs with constant tugging on the follicles (as seen with tightly braided hair or “corn rows”) is often reversible, but can become permanent if the habit persists for a long period of time.  Treatment is only possible if the hair loss from traction is not extensive and if the habit of pulling is stopped.

Scarring alopecia can be caused by conditions such as Lupus, Lichen Planus, or radiation therapy. Hair loss can occur as a result of scalp trauma or cosmetic facial surgery and is often amenable to hair transplantation. Radiotherapy can cause both scarring and non-scarring hair loss and it also can be treated with surgical hair restoration if the area is localized. 

Basic Facts on Common Baldness
All humans are born with a finite number of hair follicles. The diameters of the individual hairs in our follicles increase as we grow from infancy to adulthood. However, no matter what we eat, what our lifestyles may be, or what kinds of vitamins we take, we never grow any new hair follicles.

At puberty, most men have a low, broad hairline that usually recedes to its mature position by the age of 20 to 22 and then stabilizes.  In men with a genetic tendency to go bald, this hairline will continue to recede and new areas of thinning may occur.  Severe illness, malnutrition, or vitamin deficiency can speed or exacerbate the process of genetic hair loss, but this hair loss occurs in perfectly healthy men and is generally not a sign of disease. The common hereditary form of hair loss is also referred to as androgenetic alopecia, common baldness, or male pattern hair loss.  It is only in recent years, with our greater knowledge of genetics and the chemistry of sex hormones, that we have begun to understand the causes.  It is important to note that common genetic baldness also occurs in women, but generally it appears differently than it does in men.  

In androgenetic alopecia, the hormone DHT, a byproduct of testosterone, affects the follicles that produce terminal hairs in certain parts of the scalp.  Under the influence of DHT, susceptible follicles first produce thinner, shorter hairs with weaker shafts. Eventually, these follicles produce only fine, almost invisible, vellus hairs, and they may die out altogether. Androgenetic alopecia requires three conditions for its occurrence: the genes for hair loss, male hormones in adequate quantities, and time.

Genes
A gene is a single bit of chemically encoded hereditary instruction that is located on a chromosome and represents a tiny segment of DNA. Chromosomes occur in pairs (humans have 23 pairs), and every individual inherits one set of chromosomes from each parent.  The genetics of androgenetic alopecia is complicated and hair loss is thought to involve more than one gene.  When several genes govern a trait, it is called polygenic. Genes that are located on the X- or Y-chromosomes are called sex-linked.  Genes on the other 22 pairs of chromosomes are called autosomal.  It is currently believed that the genes governing common baldness are autosomal.  This means that the baldness trait can be inherited from the mother’s or the father’s side of the family. 

The commonly held notion that baldness comes only from the mother’s side of the family is incorrect, although for reasons not fully understood, the predisposition inherited from the mother is of slightly greater importance than that inherited from the father.  The term "dominant" means that only one gene of a pair is needed for the trait to show up in the individual. A "recessive" gene means that both genes must be present in order for the trait to be expressed.  The genes involved in androgenetic alopecia are believed to be dominant. 

Just because a person has the genes for baldness, it does not mean the trait will manifest itself and the person will actually become bald.  The ability of a gene to affect one’s characteristics, i.e. be visible in a particular individual, is called "expressivity."  Expressivity relates to a number of factors; the major ones being hormones and age, although stress and other factors yet undetermined, may play a role.    

None of the genes responsible for male pattern baldness have yet been identified.  This suggests that any kind of genetic engineering to prevent common baldness is still many years away. Even if the gene is identified, scientists must still figure out how to control or change them.

Hormones
Hormones are biochemical substances produced by various glands, such as the pituitary, adrenal and testes, that work on distant sites throughout the body, by secreting their products directly into the bloodstream.  These chemicals are very powerful and minute amounts of them have profound effects upon the bodily functions. 

The primary male sex hormone is testosterone. Testosterone and other related hormones that have masculinizing effects are produced primarily in the testicles. This means that the hormone levels that are seen in adults do not reach significant levels until the testicles develop and enlarge during puberty. These hormones are the cause of many changes that occur in puberty: deepening of the voice, growth of facial hair, development of body odor and acne, change in the muscular development, and change in body shape.  These hormones can also cause baldness. The presence of androgens, testosterone, and its related hormone DHT, cause some follicles to regress and die. In addition to the testicles, the adrenal glands located above each of our kidneys, produce androgenic hormones; this is true for both sexes.  In females, ovaries, like testicles, are a source of hormones that can affect hair.

The relationship between a man’s testicles and hair loss has been recognized for centuries. In societies that had harems, guards were castrated to prevent sexual activity between the guards and women of the harem.  In all of those societies, it was observed that men who were castrated before puberty did not become bald.  Early in the 20th century, castration was common treatment for patients with certain types of mental illness as it seemed to have a calming effect on their personality. It was also noted that these patients did not become bald.

A psychiatrist discovered the specific relationship between testosterone and hormonally induced hair loss during this time.  The doctor noted that a castrated, mentally ill patient had a full head of hair, while the identical twin brother of that patient was completely bald. The doctor decided to determine the effect of treating his patient with testosterone, which had recently become available as a drug.  He injected his patient, the hairy twin, with testosterone to see what would happen. Within weeks, the hairy twin began to lose all but his wreath of permanent hair, just like his normal twin. The doctor stopped administrating testosterone; however, his patient never regained his full head of hair.

The hormone believed to be most directly involved in androgenetic alopecia is dihydrotestosterone (DHT).  DHT is formed by the action of the enzyme 5-a reductase on testosterone.  DHT acts by binding to special receptor sites on the cells of hair follicles to cause the specific changes associated with balding.  DHT decreases the length of the anagen (growing) cycle of the hair and increases the telogen (resting) phase, so that with each new cycle the hair shaft becomes progressively smaller. This process is referred to as “miniaturization”.      

In men, 5-a reductase activity is higher in the balding area.  Women have half the amount of 5-a reductase overall as compared to men, but have higher levels of the enzyme aromatase, especially in their frontal hairlines.  Aromatase decreases the formation of DHT, and its presence in women may help to explain why female hair loss is somewhat different than hair loss in men.  

Time
The mere presence of the necessary genes and hormones is insufficient to cause baldness. Hair loss also requires exposure of susceptible hair follicles to the responsible hormones over time. The length of time required for hair loss to start due to hormone exposure varies from one individual to another, and relates to a person’s genetic expression and to the levels of testosterone and DHT in his bloodstream.  Significantly, hair loss does not occur all at once, but tends to be cyclical. People who are losing their hair experience alternating periods of slow hair loss, rapid hair loss, and even long periods of relative stability. The progression of androgenetic hair loss, however, will generally continue over ones lifetime. The factors that cause the rate of loss to speed up or slow down are, for the most part, unknown.

Stress

When the body experiences stress caused by a traumatic experience, nutritional deficiency, or illness, the rate of hair loss can increase. Women's hair seems to be more sensitive to the effects of stress than men's hair. This may be because women with a genetic predisposition towards hair loss usually have a higher percentage of fragile, miniaturized hair. It is important to note that stress generally causes the type of hair loss referred to as telogen effluvium.  This is very different from androgenetic alopecia.  Telogen effluvium is the reversible shedding of hair in the resting phase when the body senses that it needs to divert its energies elsewhere. Therefore, stress temporarily changes the amount of hair that is shed, but the lost hair is likely to grow back.

Hair Loss Fiction 

Lack of Blood Supply
Some assert that a lack of blood supply contributes to hair loss. Bald skin gradually loses some of its blood supply and, consequently, it becomes thin and shiny. These changes, however, are secondary to the loss of hair, not the other way around.   When hair follicles are transplanted into thin bald skin, or scar tissue, both of which have a relatively poor blood supply, the presence of the grafted hair causes the local blood supply to gradually increase.

Clogged Pores

This claim usually accompanies microscopic photographs of an empty follicle clogged with a heaped up waxy substance that prevented the hair from growing. There is no scientific evidence that clogged pores interfere with hair growth. Common sense is sufficient to refute these claims. Why would pores be clogged on the top of the scalp and not on the back and sides?  And if clogged pores caused baldness, women would be as bald as men.

Hats and Hair Loss

    
Folklore says that men who constantly wear hats are more likely to become bald, as hats prevent air from circulating to the head. Like other tissues in the body, hair follicles get their oxygen through the bloodstream, rather than from ambient air. 

Snake Oil Remedies and other Magic Cures