The Production of Hair
The hair follicle is the factory where the hair and the hair coloring are produced. As you can see from the drawing, it is a complex mechanism.
The activity of each follicle in human beings is independent of the others (a mosaic pattern). Some animals shed their hair when warm weather comes: all the follicles go into the telogen or resting stage at one time. Human beings with healthy follicles, however, usually do not shed great amounts of hair. Since ninety percent of healthy hair follicles are in the growing stage at all times, no dramatic loss of hair is evident.
The hair matrix at the base of the follicle is where the action takes place. The cells in this area produce keratin, the tough protein of which the hair is made, and melanin which stains the keratin giving the hair its color. This action takes place only during the growing stage of the hair cycle.
You can also see in the drawing that the follicle is nourished by a network of capillaries. These capillaries are the delivery system bringing nutrients (amino acids, vitamins, minerals) to the base of the follicle. The amount of blood available to the scalp and therefore to the follicles is determined by the health of the capillaries in the scalp and the arteries in the neck and temples.
Hair synthesis and melanin production are complex processes carried on deep in the follicle's core. Superficial cures for baldness like shampoos to "unclog" the follicles or tonics with "active ingredients" to stimulate hair growth just don't work.
The Role of Heredity
In order to interpret the biological role of heredity in hair loss it is necessary to differentiate between heredity and predisposition. Heredity is the genetic potential you are born with: eye color, skin color, hair color. These are the biological givens that are on your driver's license.
On the other hand, predisposition is the tendency of the body to acquire certain disorders: obesity, diabetes, hair loss. These are the things you don't like about yourself when you have an examination or look in the mirror.
Can you reverse predisposition? You can't eliminate the predispositions of the body but you can often contain them. For example, if you have the predisposition to obesity or diabetes, you can elect to change your life style. You can go on a low-calorie diet stressing fruits and vegetables. You can also exercise every day or at least keep active.
The same is true about the predisposition to hair loss. Rogaine, Propecia, and Dutasteride (Avodart) will all counteract the predisposition to baldness. My approach is also based on the idea that a change in life style - the scalp exercise - will slow down or stop the tendency to baldness. My belief is that predisposition, at least as far as baldness is concerned, is not destiny.
The approximately one hundred thousand hairs on the human scalp once they leave the hair canal are biologically dead. They can be dyed and curled and straightened, but they cannot be coaxed back to luxuriant teenage health by anything a barber or a beautician or a health food store can offer. Please browse around the other pages on this Web site for ideas that might legitimately help you to halt hair loss and possibly grow new hair.
An Article by Ivy Greenwell
This excerpt from from Ivy's article clarifies many aspects of the biology of baldness. I underlined sentences that I thought were especially significant. Reading this might be difficult for people not used to scientific writing, but it's worth wading through:
Well, there is at least one factor that androgenic baldness and Alzheimer's disease have in common: atherosclerosis. The lining of blood vessels produces nitric oxide (NO, as in MiNOxidol, the active ingredient in Rogaine) and possibly other hair growth factors; when this lining is damaged through the accumulation of atherosclerotic plaque, less nitric oxide (NO) is produced.
Please don't draw the wrong conclusion that a balding man is doomed to go on to Alzheimer's disease or Parkinson's. Like most men, he'll probably die of heart disease, which is a much better way to die. Also, 40% of men die before their 75th birthday, which also helps account for the lower rate of brain disease in the male population. Still, what happens in the scalp of a balding person (including inflammation and free-radical damage) does seem to bear resemblance to what probably goes on in the brain tissue of brain-disease victims.
The incidence of male pattern (androgenic) baldness has been found to be the highest among college professors, and lowest among skid-row winos. Winos are also known to have the cleanest arteries in the world (which of course doesn't save them from dying of cirrhosis of the liver). Could there be a connection? Let me remind you that alcohol is an excellent vasodilator -- there is perhaps nothing quite like alcohol for dilating those peripheral blood vessels. And vasodilatation implies nitric oxide release. (I'm not recommending that anyone take up drinking. For years now I've been haunted by the question of whether it's possible to duplicate the benefits of alcohol in a non-alcoholic way, which would be vastly preferable. For women, estrogens seem to do something very similar, but what about men?)
For unknown reasons, androgenic baldness is more common among blond men than dark-haired men and among Caucasians than among other races. First of all, however, we need to address the most obvious question: why is baldness so prevalent among men, and relatively rare among women, especially premenopausal women?
We need to look here at how hormones affect hair. Estrogens promote the growth of scalp hair, while they inhibit the growth of hair elsewhere on the body; DHT, the strong form of testosterone, promotes the growth of body hair, facial hair, but it appears to inhibit the growth of scalp hair. The amount of DHT produced in the skin in turn depends on the amount of the enzyme 5-alpha-reductase available for the conversion of testosterone to DHT. Men with congenital deficiency of 5-alpha-reductase have small prostates, do not develop prostate cancer (no case has ever been reported), have little body hair, and do not grow bald.
Women often notice increased hair loss when there is a sudden drop in estrogens: post-partum, after stopping the Pill, and at the onset of menopause. It is estimated that a woman may lose as much as 20% of her hair at menopause. Both post-partum and menopausal hair loss, however, are not classified as androgenic alopecia, but as "endocrine alopecia," which should really be called "estrogen-withdrawal alopecia."
Severely hyperandrogenic women, on the other hand, can suffer from male pattern baldness even at a young age. Still, a woman can be hyperandrogenic without necessarily showing signs of androgenic alopecia, but she may have acne and increased facial and body hair. Or a woman can have androgenic alopecia without acne and/or hirsutism. This seems to be a highly individual matter.
Typically, however, it is men who start losing hair fairly early in life, sometimes already in their twenties. Men produce a lot more DHT than women do, since obviously men produce a lot more testosterone than women do (DHEA can also serve as a raw material for DHT). But it's not the serum level of DHT that seems to matter, but the local conversion of androgens to DHT in the scalp.
Let me stress this point: it is the LOCAL excess DHT production that seems to be the root of the problem. THE SCALP FOLLICLES OF GENETICALLY SUSCEPTIBLE INDIVIDUALS HAVE MORE OF THE ENZYME 5-ALPHA-REDUCTASE, RESPONSIBLE FOR THE CONVERSION OF TESTOSTERONE TO DHT. Most women are protected by having (1) less testosterone, (2) less 5-alpha-reductase needed to convert T to DHT, and also (3) by having more aromatase, the enzyme that converts testosterone to estradiol.
It is interesting to note that male teenagers and young men, with their tremendously high testosterone output (T production begins to decline very gradually after the age of 25) tend to have a full head of hair but generally not that much chest hair and facial hair. On the other hand, it's not unusual to see lots of chest hair and a full flowing beard on a severely balding middle-aged man. Apparently the local production of DHT, perhaps as compensation for low serum androgens, is a significant factor here. We do not yet understand how serum DHT and peripheral DHT are related, but one hypothesis is that there is an inverse relationship. It's just a hypothesis. Estrogens are vasodilators: they promote the release of NO from the blood vessel lining. It's also possible that estrogens increase superoxide dismutase (SOD) activity (at least that's one of the effects of the birth-control pill). SOD quenches the superoxide radical, a very nasty little beastie that apparently inhibits NO release.
DHT acts in a more perfidious way. Here is one emerging view of it: DHT seems to induce class-II antigens within the follicle. The immune system then perceives the follicle as a "foreign body," and targets it for destruction. Progesterone inhibits 5-alpha-reductase, and it can compete with other androgens for androgen receptors (progesterone could be classified as a "non-masculinizing androgen"). Topical progesterone can thus arrest the progression of baldness, but it doesn't promote regrowth. I repeat: there is no evidence that progesterone promotes regrowth. Just decreasing DHT in the scalp can at best arrest the progression of baldness. Proscar (finasteride) also decreases DHT by inhibiting 5-alpha-reductase. Proscar produces close to 70% reduction in serum DHT, but only about 34% reduction in skin DHT. Still, virtually all men taking Proscar (5 mg finasteride) report that the progression of baldness is arrested. But is a big reduction of serum DHT beneficial, or can it in fact be harmful? (Hint: DHT can't be aromatized to estradiol, and estradiol has been implicated in prostate cancer. We discuss it later in this issue - see the comment by Dr. Zava.)
CORTISOL and cortisone, the so-called "stress hormones," are also androgens and are possibly implicated in baldness. We know for sure that they are involved in acne. Anecdotally, stress is known to cause hair loss. One study (Schmidt 1994) did find SIGNIFICANTLY ELEVATED CORTISOL IN ANDROGENIC ALOPECIANS, BOTH MALE AND FEMALE, as compared with controls. It also found alopecians to have significantly elevated androstenedione. In women there was also very frequent hypothyroidism and/or elevated prolactin (it's possible that prolactin stimulates the production of androgens). Balding men, on the other hand, had higher serum estradiol than controls.
Schmidt makes a very big point of the finding that women suffering from androgenic alopecia do not necessarily have higher serum androgens (other than cortisol, generally not classified as an androgen, though it should be). She thinks that THE MAIN HORMONAL DISTURBANCE LINKED TO FEMALE ALOPECIA IS HYPOTHYROIDISM. It's likely that hypothyroidism leads to abnormalities in both estrogen and androgen metabolism. I'm amazed that this study didn't look at insulin, since elevated insulin has been linked to alopecia in hyperandrogenic women. Anecdotally, lowering insulin with drugs and/or diet does seem to improve hair growth in both men and women. [Read my paragraphs on insulin resistance in the Nutrition page sidebar.]
As you can see, the situation gets more and more complicated the more hormones you look at. Finally you just want to throw up your hands and say, "OK, it looks like all the hormones are out of whack." To put it more formally, androgenic alopecia is a multi-hormonal disorder. You can't just say "too much DHT."
Malnutrition and stress can obviously cause hair loss, but it appears that the primary causes are genetic-hormonal-immunological and vascular (it's not really possible to separate the endocrine system from the immune system from the nervous system and so forth). In other words, to preserve our hair, we must keep DHT and cortisol at bay and strive to preserve clean arteries.
There's a lot of heavy material to absorb in this excellent article by Ivy Greenwell. I'm sure those looking for a quick fix for hair loss problems will be impatient trying to extract the meaning from it. It would be neat if hair loss could be easily solved - a topical elixir, a miracle drug; then we could all relax and read the funny paper.
A look at how hair follicles emerge from the scalp. These naturally occurring groups of two, three, or four hairs are called follicular units.