Ninety-five percent of hair loss in men is caused by androgenetic alopecia, male pattern baldness. It is not caused by clogged pores, lack of oxygen in scalp blood vessels, or wearing a tight ball cap. As noted in the hair loss history section
June 13, 2014 (Newswire) - Ninety-five percent of hair loss in men is caused by androgenetic alopecia, male pattern baldness. It is not caused by clogged pores, lack of oxygen in scalp blood vessels, or wearing a tight ball cap. As noted in the hair loss history section, male pattern baldness is driven by 3 factors, of which the first one is the most necessary.
1-Androgens (male hormones)
DHT and Miniaturization
Although Hamilton's observations (see History) of eunuchs (castrated men and men who failed to develop sexually) led him to understand that androgens were the culprit behind male pattern baldness, it wasn't until the 1970s or 80s that scientists began to understand that when an enzyme called 5-alpha-reductase combined with testosterone, it created dihydrotestosterone, or DHT. Dihydrotestosterone causes hair to fall out through a gradual miniaturization process that begins along the same patterns as outline in the Norwood Charts: either at the temples and crown as Norwood's "Regular Type," or as Type A Variant where DHT attacks the hair follicles in the temple and frontal region, gradually sweeping it's way backwards over the mid-scalp, but not affecting the crown until the last stages.
"This DHT is harmful to hair follicles and "attacks" it, slowly breaking it down, reducing the diameter and length, so that the hair follicle becomes smaller and smaller while the color fades away. This kind of hair is known as vellus hair. Soon, this vellus hair will fall out and will not be replaced by new hair."
"In men with MPHL all the hairs in a DHT affected area may eventually (but not necessarily) become involved in the process and may with time cover the region with fine (vellus) hair. Pigment (color) production is also terminated with miniaturization so the fine hair becomes lighter in color. The lighter color, miniaturized hairs cause the area to first appear thin."
In men, hair that grows near the temple region, front, mid-scalp (top) and crown (back top of head where it starts to go in a 90 degree angle toward the neck) are most susceptible to DHT. Hair on the back and sides of the head (above the ear but below the top, are the LEAST susceptible to hair loss.
In addition, miniaturization and detectable hair loss is not evident to the naked eye until more than 50% of normal (non-miniaturized) hair is lost. As a result, many men/women do not seek help until significant miniaturization has already taken place.
Enzyme 5 Alpha Reductase
5-Alpha reductase is a naturally occuring enzyme involved in steroid metabolism. When it combines with testosterone, it becomes dihydrotestosterone, DHT, which scientist recognize as the culprit behind male pattern hair loss. DHT attacks the hair follices as demonstrated in Fig 1, slowly breaking them down, reducing the diameter of the follicle until it eventually falls out, never to return.
There are 2 types of 5-alpha-reductase. Type I and Type II. [Note] Finasteride only inhibits Type II 5-alpha-reductase, which means it will never be 100 percent effective in stopping DHT. There are medications that stop both, including dutasteride.
As Dr. Hamilton noted in 1941, genetic disposition was a factor in male pattern baldness. Dermatologists and hair transplant doctors would often tell their patients that if you wanted to know how your hair loss pattern would look like, or how severe it would get, take a collective view of all the males in your family. However, this "guesswork" didn't answer the quantifying questions of what are my chances of going bald? A 2004 study that looked at "Family History and Risk of Hair Loss" determined that:
"...men whose fathers had hair loss were 2.5 times as likely to have had some level of hair loss compared to men whose fathers had no hair loss.
"Likewise, men whose fathers had hair loss were twice as likely to have hair loss than men whose fathers had no hair loss even after adjusting for age. Conclusion: Results suggest that the probability of male pattern hair loss is dependent on family history and age. Hair loss in a man's father also appears to play an important role in increasing a man's risk of hair loss, either in conjunction with a history of hair loss in the mother or hair loss in the maternal grandfather."
So that leads into another aspect of the genetics question which is, which side is more responsible for my hair loss? My mother's or my father's? Many hair transplant doctors and dermatologists will tell you it's a myth to assume it's either one, especially the maternal side which has been the popular "suburban myth" among men for decades. It's nonsense talk, they say. Look at both sides. Well, maybe, but maybe it's not nonsense.
Take a look at a 2005 German study that says heredity hair loss was partially traced back "...to a series of areas on various chromosomes. In an area where the largest contribution was suspected lay the gene for the androgen receptor. " - The gene for this androgen receptor lays with the X chromosome, which men inherit from their mothers, leading one to assume that men's hairlines might lean more towards their maternal grandfather, instead of looking more like their paternal grandfather.
But even the German study says, 'maybe.' The study is quick to hedge themselves by saying that the hereditary genes for male pattern baldness are not that simple and there can be more than one suspect gene or culprit gene that is guilty. "We have indications that other genes are involved which are independent of the parents' sex," Prof. Nthen stresses.. "The hereditary defect can therefore sometimes also be passed on directly from father to son."
Incidence of male pattern baldness, including crown hair loss, and age has not been definitively determined. For example, WebMD says that by age 35, 2/3 of all men will experience hair loss to some degree. By age 50, 85 percent of all men will experience thinning hair to a larger degree while an unfortunate 25 percent of young men under the age of 21 will experience some degree of hair loss.
According to the International Society of Hair Restoration Surgeons, 20 percent of men in their 20s will have hair loss, 30 percent in their 30s, and so, adding 10 percent of the population for each decade. Using this scale, 50 percent of men in their 50s will have hair loss and 90 percent in their 90s will have hair loss.
In building his classification chart, Norwood was able to get exact numbers for each chart class of hair loss based on age. Notice that in his findings, 3 out of 165 men (2 percent) age 18-29 are already a class 5. In the 40 to 49 age category, 15 men were class 4, and 5 were class 7, and so on. In the 70 to 79 group, 64 out of 102 men had class 3 or higher male pattern baldness.
Unfortunately, his study only looked at 1,000 white males, and did not include blacks, asians, pacific islanders, latins and men from middle eastern descent.