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Alopecia
ICD-10 {{{ICD10}}}
ICD-9 {{{ICD9}}}
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Baldness involves the state of lacking hair where it often grows, especially on the head. The most common form of baldness is a progressive hair thinning condition called androgenic alopecia or 'male pattern baldness' that occurs in adult male humans and other species. The severity and nature of baldness can vary greatly; it ranges from male and female pattern alopecia (androgenetic alopecia, also called androgenic alopecia or alopecia androgenetica), alopecia areata, which involves the loss of some of the hair from the head, and alopecia totalis, which involves the loss of all head hair, to the most extreme form, alopecia universalis, which involves the loss of all hair from the head and the body. Treatments for the various forms alopecia have limited success, but typical male pattern baldness is now a very preventable, and reversible (to a certain extent) condition. Thousands of individuals today make use of clinically proven treatments such as Avacor, Propecia and the new Rogaine Foam, to show noticeable regrowth and prevent any further loss. As a general rule, the more hair you've lost the harder it is to restore, but the treatments will help the vast majority of users, and there are new technologies in cosmetic transplant surgery and hair replacement systems that are completely undetectable.

There are several other kinds of baldness:

  • Traction alopecia is most commonly found in people with ponytails or cornrows who pull on their hair with excessive force. Wearing a hat shouldn't generally cause this, though it is a good idea to let your scalp breathe for 7 hours a day[How to reference and link to summary or text].
  • Traumas such as chemotherapy, childbirth, major surgery, poisoning, and severe stress may cause a hair loss condition known as telogen effluvium.[1]
  • Some mycotic infections can cause massive hair loss.[2]
  • Alopecia areata is an autoimmune disorder also known as "spot baldness" that can result in hair loss ranging from just one location (Alopecia areata monolocularis) to every hair on the entire body (Alopecia areata universalis).
  • Localized or diffuse hair loss may also occur in cicatricial alopecia (lupus erythematosus, lichen plano pilaris, folliculitis decalvans, central centrifugal cicatricial alopecia, postmenopausal frontal fibrosing alopecia, etc.). Tumours and skin outgrowths also induce localized baldness (sebaceous nevus, basal cell carcinoma, squamous cell carcinoma).

Etymology

The term alopecia (al-oh-PEE-she-uh) is formed from the Greek αλώπηξ (alopex), meaning fox. The origin of this usage is because this animal sheds its coat twice a year.

The term bald likely derives from the English word balde, which means "white, pale", or Celtic ball, which means "white patch or blaze", such as on a horse's head.[3]

Background

The average human head has about 100,000 hair follicles. Each follicle can grow about 20 individual hairs in a person's lifetime.[4] Average hair loss is about 100 strands a day.

Male pattern baldness is characterized by hair receding from the lateral sides of the forehead, known as "receding hairline".

An additional bald patch may develop on top (vertex). The trigger for this type of baldness (called androgenetic alopecia) is DHT, a powerful sex hormone and hair growth promoter that can adversely affect the hair and prostate.[5]

Assessment

Male pattern baldness is classified on the Hamilton-Norwood scale I-VIII.

Incidence

Incidence of pattern baldness varies from population to population based on genetic background. Environmental factors do not seem to affect this type of baldness greatly. One large scale study in Maryborough, in central Victoria (Australia) showed the prevalence of mid-frontal hair loss increases with age and affects 57% of women and 73.5% of men aged 80 and over.


Causes

The mechanism by which DHT accomplishes this is not yet understood. In genetically-prone scalps, DHT initiates a process of follicular miniaturization. Through the process of follicular miniaturization, hair shaft width is progressively decreased until scalp hair resembles fragile vellus hair or "peach fuzz" or else becomes non-existent. Onset of hair loss sometimes begins as early as end of puberty, and is mostly genetically determined. It was previously believed that baldness was inherited. While there is some basis for this belief, both parents contribute to their offspring's likelihood of hair loss. Most likely, inheritance is technically "autosomal dominant with mixed penetrance" (see 'baldness folklore' below)


  • Hypothyroidism can cause hair loss, especially thinning of the outer third of the eyebrows
  • Temporary loss of hair can occur in areas where sebaceous cysts are present for considerable duration; normally one to several weeks in length.



Psychological causes of hair loss

Evolutionary theories of male pattern baldness

Male silverback Gorilla

There is no consensus regarding the details of the evolution of male pattern baldness. Most theories regard it as resulting from sexual selection. A number of other primate species also experience hair loss following puberty, and some primate species clearly use an enlarged forehead, created both anatomically and through strategies such as frontal balding, to convey increased status and maturity. The assertion that MPB is intended to convey a social message is supported by the fact that the distribution of androgen receptors in the scalp differs between men and women, and older women or women with high androgen levels often exhibit diffuse thinning of hair as opposed to male pattern baldness.

One theory, advanced by Muscarella and Cunningham, suggests baldness evolved in males through sexual selection as an enhanced signal of aging and social maturity, whereby aggression and risk-taking decrease and nurturing behaviours increase.(1) This may have conveyed a male with enhanced social status but reduced physical threat, which could enhance ability to secure reproductive partners and raise offspring to adulthood.

In a study by Muscarella and Cunnhingham, males and females viewed 6 male models with different levels of facial hair (beard and moustache or clean) and cranial hair (full head of hair, receding and bald). Participants rated each combination on 32 adjectives related to social perceptions. Males with facial hair and those with bald or receding hair were rated as being older than those who were clean-shaven or had a full head of hair. Beards and a full head of hair were seen as being more aggressive and less socially mature, and baldness was associated with more social maturity.

Approaches to baldness

Psychological effects

The psychological effects for individuals experiencing hair loss vary widely. Some people adapt to the change comfortably, while others have severe problems relating to anxiety, depression, social phobia, and in some cases, identity change.

StoryMusgrave

Retired NASA Astronaut Story Musgrave.

Alopecia induced by cancer chemotherapy has been reported to cause changes in self-concept and body image. Body image does not return to the previous state after regrowth of hair for a majority of patients. In such cases, patients have difficulties expressing their feelings (what is called alexithymia) and may be more prone to avoiding family conflicts. Family therapy can help families to cope with these psychological problems if they arise.[6]

Psychological problems due to baldness, if present, are typically most severe at the onset of symptoms.[7]

Some balding men may feel proud of their baldness, feeling a kindred relationship with famous charismatic bald men such as Telly Savalas, Patrick Stewart, Sean Connery, Yul Brynner, Billy Corgan, Vin Diesel, Michael Chiklis, Michael Stipe, Ross Kemp, Jason Alexander, Larry David, Danny De Vito, Ben Kingsley or Bruce Willis; or politicians such as Ed Koch, John Reid, Menzies Campbell and James Carville; or sportsmen such as wrestler Stone Cold Steve Austin, footballers Zinedine Zidane, Bobby Charlton or tennis star Andre Agassi. Much of these celebrities' perceived masculinity and handsomeness derives from their most obvious distinguishing feature. Baldness has, in recent years, in any case become less of a (supposed) liability due to an increasing fashionable prevalence of very short, or even completely shaven, hair among men, at least in western countries. This is even true for women, as shown by the case of singer Sinead O'Connor who has a shaven head.

Many companies have built a successful business selling products that reverse baldness, by allegedly regrowing hair, transplanting hair or selling hairpieces. There is very little evidence that any of those which claim hair regrowth actually work.

Preventing and reversing hair loss

Main article: Baldness treatments

In the USA, there are only 2 treatments that have been approved by the FDA (Food and Drug Administration) and one product that has been cleared by the FDA for the treatment of androgenetic alopecia, otherwise known as male or female pattern hair loss. The two FDA approved treatments are finasteride (marketed for hair loss as Propecia) and minoxidil.

Propecia

Merck Pharmaceuticals sought to find the smallest effective quantity of finasteride and test its long-term effects on 1,553 men between ages 18 and 41 with mild to moderate thinning hair. Based on their research, 1mg daily was selected, and after 2 years of daily treatment, over 83% of the 1,553 men experiencing male hair loss had actually maintained or increased their hair count from baseline. Visual assessments concluded that over 80% had improved appearances.

Minoxidil

Minoxidil was first used in tablet form as a medicine to treat high blood pressure, but it was noticed that some patients being treated with Minoxidil experienced excessive hair growth (hypertrichosis) as a side-effect. Further research showed that by applying Minoxidil in solution form directly to the scalp, it could prove to be beneficial to those experiencing topical hair loss.

FDA clinical trials showed that 65% of men with androgenetic alopecia maintained or increased their hair count from the use of minoxidil 5% in liquid form. 54% of these men experienced moderate to dense regrowth and 46% experienced hair loss stabilisation and mild regrowth.

In controlled clinical studies of women aged 18-45, 2 out of 3 women with moderate degrees of hereditary hair loss reported re-growth after using 2% minoxidil. Initial results occur at 4 months with maximum results occurring at 8 months.

LaserComb

The FDA's test report said subjects who used the treatment "had significantly greater increases in mean terminal hair density" than those who used placebo in the tests.

As the device's name suggests, it combines a low-level laser with a comb. When drawn through the hair, the laser strikes the scalp to promote hair growth.<p> The LaserComb is the only drug-free product meant for home use in combating hair loss that's won the endorsement of the Food and Drug Administration.

Treatment Combinations

A combination of the FDA approved hair loss treatments is thought to be the most effective form of non-surgical treatment for hair loss. [How to reference and link to summary or text]

Surgery

Surgery is another method of reversing hair loss and baldness, although it may be considered an extreme measure. The surgical methods used include hair transplantation, whereby hair-producing follicles are taken from the back and sides of the head and injected into bald or thinning areas.

Hair Multiplication

Looking forward, the prospective treatment of hair multiplication/hair cloning, which extracts self-replenishing follicle stem cells, multiplies them many times over in the lab, and microinjects them into the scalp, has been shown to work in mice, and is currently under development, expected by some scientists to be available to the public in 2009–2015. Subsequent versions of the treatment are expected by some scientists to be able to cause these follicle stem cells to simply signal the surrounding hair follicles to rejuvenate. See Baldness treatments

In October 2006, UK biotechnology firm Intercytex announced they have successfully tested a method of removing hair follicles from the back of the neck, multiplying them and then reimplanting the cells into the scalp (Hair multiplication). The initial testing resulted in 70% of male patients regrowing hair. This treatment method is expected to be available to the public by 2009 [1][2].

In January 2007, Italian stem-cell researchers say they've come up with a new technique for curing baldness. Pierluigi Santi of a Genoa clinic said stem cells could be used to "multiply" hair roots. He said the clinic would be ready to perform its first hair transplants on priority patients - those who have lost their hair in fires or other accidents - within a few months. After that, he said, "we'll open our doors to paying customers". Santi's approach works by splitting roots and growing new follicles.

Ketoconazole

Topical application of ketoconazole, which is both an anti-fungal and a potent 5-alpha reductase inhibitor, is often used as a supplement to other approaches.1

Unsaturated Fatty Acids

Particular unsaturated fatty acids such as gamma linolenic acid are 5 alpha reductase inhibitors if taken internally. [3]

Placebos

Interestingly, placebo treatments in studies often have reasonable success rates, though not as high as the products being tested, and even similar side-effects as the products. For example, in Finasteride (Propecia) studies, the percent of patients with any drug-related sexual adverse experience was 3.8% compared with 2.0% in the placebo group.[8]

Exercise

Studies done on subjects of various ages suggests that weight training alone may increase testosterone in studies where aerobic exercise (only) was compared to either weight training (only) or a moderately sedentary life. [4]; [5] [6] [7] One study suggests that both heavy exercise and increased fat intake, in combination, are required for increased free testosterone in strength trainers. This would help them build muscle, but may cause susceptible individuals to lose hair. [8]

However, there is at least one study that indicates a decline in free testosterone combined with an increase in strength due to an (unspecified) strength training regime.[9]

Stress Reduction

Stress reduction can be helpful in slowing hair loss. (see Baldness Folklore)

Immunosuppressants

Immunosuppressants applied to the scalp have been shown to temporarily reverse alopecia areata, though the side effects of some of these drugs make such therapy questionable. [9][10]

Saw Palmetto

Saw Palmetto (Serenoa repens) is an herbal DHT inhibitor often claimed to be cheaper and have fewer side effects than finasteride and dutasteride. Unlike other 5alpha-reductase inhibitors, Serenoa repens induces its effects without interfering with the cellular capacity to secrete PSA.[10] Saw palmetto extract has been demonstrated to inhibit both isoforms of 5-alpha-reductase unlike finasteride which only inhibits the (predominant) type 2 isoenzyme of 5-alpha-reductase.[11][12][13]

Polygonum Multiflorum

Polygonum Multiflorum is a traditional Chinese cure for hair loss. Whether the plant itself is useful, the general safety and quality control of herbs imported from China can be questionable.

Beta Sitosterol

Beta Sitosterol, which is a constituent in many seed oils, can help to treat BHP by lowering cholesterol. If used for this purpose, an extract is best. Consuming large amounts of oil to get at small quantities of beta sitosterol is likely to exacerbate male pattern baldness.

Resveratrol

Resveratrol, from grape skins.

Anti-Androgens

While drastic, broad spectrum anti-androgens such as flutamide are sometimes used topically. Flutamide is potent enough to have a feminizing effect in men, including growth of the breasts.

Hedgehog Agonists

In March 2006, Curis announced that it had received the first preclinical milestone, a $1,000,000 cash payment, in its hair growth program with Procter & Gamble Pharmaceuticals, a division of The Procter & Gamble Company. The program is focused on the potential development of a topical Hedgehog agonist for hair growth disorders, such as male pattern baldness and female hair loss. The curis hairloss research program was shut down in may 2007 because the process did not meet the proper safety standards.[14]

WNT Gene Related

In May 2007, US company Follica Inc, announced they have licensed technology from the University of Pennsylvania which can regenerate hair follicles by reawakening genes which were once active only in the embryo stage of human development.[11] [12] [13] [14] [15][16]

Concealing hair loss

Head

One method of hiding hair loss is the "comb over", which involves restyling the remaining hair to cover the balding area. It is usually a temporary solution, useful only while the area of hair loss is small. As the hair loss increases, a comb over becomes less effective. When this reaches a stage of extreme effort with little effect — it can make the person the object of teasing or scorn.

Another method is to wear a hat or a hairpiece — a wig or toupee. The wig is a layer of artificial or natural hair made to resemble a typical hair style. In most cases the hair is artificial. Wigs vary widely in quality and cost. In the United States, the best wigs — those that look like real hair — cost up to tens of thousands of dollars. Organizations such as Wigs for Kids and Locks of Love collect individuals' donations of their own natural hair to be made into wigs for young cancer patients who have lost their hair due to chemotherapy or other cancer treatment in addition to any type of hair loss.

Eyebrows

Though not as common as the loss of hair on the head, chemotherapy, hormone imbalance, forms of alopecia, and other factors can also cause loss of hair in the eyebrows. Artificial eyebrows are available to replace missing eyebrows or to cover patchy eyebrows.

Embracing baldness

File:Telly 02.jpg

Of course, instead of concealing hair loss, one may embrace it. A shaved head will grow stubble in the same manner and at the same rate as a shaved face. Many celebrities and athletes shave their heads. The general public has become accepting of the shaved head also.

Female baldness is less socially accepted.

Baldness folklore

There are many myths regarding the possible causes of baldness and its relationship with one's virility, intelligence, ethnicity, job, social class, wealth etc. While skepticism is warranted due to lack of scientific validation, some of these myths may have a degree of underlying truth.

  • "You inherit baldness from your mother's father."
    Previously, early baldness of the androgenic type was thought to be sex linked dominant in males and to be sex linked recessive in females.
    Research suggests that the gene for the androgen receptor, which is significant in determining probability for hair loss, is located on the X chromosome and so is always inherited from the mother's side.[15]There is a 50% chance that a person shares the same X chromosome as their maternal grandfather. Because women have two X chromosomes, they will have two copies of the androgen receptor gene while men only have one. However research has also shown that a person with a balding father also has a significantly greater chance of experiencing hair loss.[16][17]

Another model for the inheritance of baldness is "Autosomal dominant with mixed pentrance. That is, you can get it from either parent and it presents variably.

  • "Intellectual activity or psychological problems can cause baldness."
    This myth probably was inspired by the fact that the human brain is located inside the skull, very close and just below where hair grows, and so it was thought that the use and abuse as well as mental diseases could have negative effect on hair growth and number.[How to reference and link to summary or text] It may also be due to the fact that cholesterol is involved in the process of neurogenesis and also the base material from which the body ultimately manufactures DHT.
    This is sometimes used as a stereotype in films, where the more intellectual or rather frustrated characters are most usually portrayed as bald and generally unattractive, as opposed to the main characters which are usually portrayed as attractive, fit, mentally stable and generally with no apparent hair problems.
    This same myth normally extends to considering people having intellectual jobs more prone to baldness problems compared to manual laborers, sometimes further extending the myth to male college or university students when compared to workers of the same age.[How to reference and link to summary or text] The myth is suspect because counterexamples can be found in any case.
    There is evidence, confirmed by cross cultural studies, for an association between androgen levels and intellectual ability. These findings are controversial due to their implications regarding psychology and gender.
    Total testosterone exhibits a positive relation to tactual-spatial abilities and to the degree of lateralization. Total testosterone is negatively correlated with verbal fluency. Testosterone in the saliva is also significantly positively correlated to tactual-spatial test scores and, in addition, to field independence. DHT and the ratio DHT/total testosterone are positively related to verbal fluency and negatively to the degree of lateralization of tactual-spatial performance.[18]
  • "One's ethnicity can increase the chances of going bald."
    This idea has been seen as somewhat descriminative and sensitive in nature, however studies have shown that men of Greek or Macedonian heritage have the highest percentage of bald or balding men. (age group 16-28, typical, non married, non-drug using, males) Studies done between 6 countries in Western Europe, incl. Britain, France, Italy, Germany, Spain and Ireland and 4 countries in Eastern Europe including Greece, Macedonia, Bulgaria and Romania show that Greek men of the same age group and study period had the highest percentage of full crown baldness or Alopeciae totalis (front, top and back) Another typical study during the same period showed that Greek men, 1700 out of 2457 total studied males also suffered the highest amount of random alopecia areata among men (aged 16-28, typical, non-drug using males)
  • "Baldness can be caused by emotional stress, sexual frustration etc."
    Emotional stress has been shown to accelerate baldness in genetically susceptible individuals.[19]
    Stress due to sleep deprivation in military recruits lowered testosterone levels, but is not noted to have effected SHBG.[20]
    Thus, stress due to sleep deprivation in fit males is unlikely to elevate DHT, which causes male pattern baldness. Whether it can cause hair loss by some other mechanism is not clear.
  • "Bald men are more 'virile' or sexually active than others."
    Levels of free testosterone are strongly linked to libido and also DHT levels, but unless free testosterone is virtually non-existent levels have not been shown to affect virility. Men with androgenic alopecia are more likely to have a higher baseline of free androgens. However sexual activity is multifactoral, and androgenic profile is also not the only determining factor in baldness. Additionally, because hair loss is progressive and free testosterone declines with age, a person's hairline may be more indicative of their past than present disposition. [21][22]
  • "Shaving hair makes it grow back stronger"
    Proposed as a popular remedy against baldness, it is very probably just an illusion similar to the one perceived after shaving one's beard or mustache. Shaving one's head doesn't increase the number of healthy hair present on the scalp, and, after the remaining hair has grown a few millimeters, no enhancement in thickness or overall quality can be observed.
  • "Frequent ejaculation causes baldness"
    There are many misconceptions about what can help prevent hairloss, one of these being that frequent ejaculation may have an influence on MPB. Ejaculation significantly lowers levels of relaxin (a 5-alpha reductase inhibitor) in a male's body. Depending on frequency, it can raise or lower plasma testosterone. [17] The claim that frequent ejaculations can cause baldness is often viewed with skepticism.
  • "Standing on one's head alleviates baldness"
    The "blood-flow" theory, which led men to stand on their heads in the 1980s, can be found in the advertising for many of the fake hairloss treatments for sale on the internet. While Minoxidil is a vasodilator and is speculated to work, in part, by increasing blood flow to hair follicles, there is no evidence that standing on one's head can alleviate baldness.
  • "Tight hats cause baldness."
    This one probably started in the military where young men entering the service were required to wear hats and soon showed signs of going bald, or at least of hair thinning. This is due to coincidental timing. The age that young men enter the military is also the same age that male pattern hair loss begins. This is due to dihydrotestosterone, not hats. Hats do cause hair breakage and, to a lesser degree, split ends. Since hats are not washed as frequently as other clothing, they can also lead to scalp uncleanliness and possible P. ovale contamination in men with naturally oily scalps.

Trivia

Krahulik Holkins, Comicon 2006

Jerry Holkins of Penny Arcade fame is bald.

  • John D. Rockefeller had an extreme case of alopecia that caused him to lose all of the hair on his face, including his eyebrows and eyelashes. Another famous person who suffers from similarly severe alopecia is Italian football referee Pierluigi Collina. Actor Patrick Stewart lost most of his hair to male-pattern baldness by age 19 (His natural "horse-shoe" of remaining hair can be seen in the film L.A. Story, along with his numerous appearances as Captain Jean-Luc Picard in Star Trek).
  • Eunuchs rarely go bald, due to to reduced hormone levels.[23]
  • Baldness is not only a human trait. Some other primates, such as chimpanzees, stump-tailed macaques, and South American nakari show progressive thinning of the hair on the scalp after adolescence. Adult stump-tailed macaques, in fact, are commonly used in laboratories for the testing of hair-regrowth treatments.
  • The different predecessors of Old World and New World vultures convergently evolved a bald head, preventing feathers from retaining material from the vulture's diet of rotting meat, as well as helping in heat regulation.[24][25]
  • The American Bald Eagle is not really bald. The feathers on the head of this bird are white, in contrast to the brown feathers of the body. The term "bald" derives from the English word balde, which means "white".
  • Little Britain actor and creator Matt Lucas has suffered from Alopecia Universalis since the age of 6 and has since utilised his situation in the creation of popular characters from Little Britain, such as Andy Pipkin.
  • Scottish Pop-punk band Firepoint 17 have a song named "The wrath of the bald prophet" referring to a person whom they disliked who happened to be bald.
  • A samba march that stormed the Carnaval of Rio in 1942, entitled "Nós, os carecas" (composed by Arlindo Marques Júnior & Roberto Roberti), had a provocative line "É dos carecas que elas gostam mais" (translation: it's the bald ones women like most.) The complete lyric is: Nós, nós os carecas/ Com as mulheres somos maiorais/ Pois na hora do aperto/ É dos carecas que elas gostam mais// Não precisa ter vergonha/ Pode tirar seu chapéu/ Pra quê cabelo? Pra quê seu Queiroz?/ Agora a coisa está pra nós, nós nós...Letras de marchinhas de Carnaval

Latest research

The LIPH gene makes LIPH, a protein that isn't thoroughly understood but seems to play a role in normal hair formation and growth"

http://www.hon.ch/News/HSN/536000.html

http://www.webmd.com/news/20061109/inherited-hair-loss-may-be-upped-by-gene-glitch

http://www.forbes.com/forbeslife/health/feeds/hscout/2006/11/09/hscout536000.html

"The so-called hairless gene works by repressing the production of a protein called wise, which can hinder the process of hair growth if it is left to accumulate."

http://news.bbc.co.uk/1/hi/health/4283302.stm

DSG4 gene

http://www.hairlosstalk.com/newsletter/article209.htm http://www.hairlosstalk.com/download/CELL1132249.pdf

WNT GENE

http://news.bbc.co.uk/2/hi/health/6661849.stm

See also


References

  • Stárka L, Cermáková I, Dusková M, Hill M, Dolezal M, Polácek V (2004). Hormonal profile of men with premature balding.. Exp Clin Endocrinol Diabetes 112 (1): 24-8. PMID 14758568.
  • Nourkrin Man research on DHT. [18] 2006.

Footnotes

  1. Nnoruka E, Nnoruka N (Oct 2005). Hair loss: is there a relationship with hair care practices in Nigeria?. Int J Dermatol 44 Suppl 1: 13-7. PMID 16187950.
  2. Pappas P, Kauffman C, Perfect J, Johnson P, McKinsey D, Bamberger D, Hamill R, Sharkey P, Chapman S, Sobel J (1995). Alopecia associated with fluconazole therapy.. Ann Intern Med 123 (5): 354-7. PMID 7625624.
  3. Harper, Douglas Entry for "bald". Online Etymology Dictionary. URL accessed on 2006-12-07.
  4. "Growth of Human Hair" Procter & Gamble, 2003.
  5. Rebora A (2004). Pathogenesis of androgenetic alopecia.. J Am Acad Dermatol 50 (5): 777-9. PMID 15097964.
  6. Poot F (2004). [Psychological consequences of chronic hair diseases]. Rev Med Brux 25 (4): A286-8. PMID 15516058.
  7. Passchier J, Erdman J, Hammiche F, Erdman R (2006). Androgenetic alopecia: stress of discovery.. Psychol Rep 98 (1): 226-228. PMID 16673981.
  8. Leyden J, Dunlap F, Miller B, Winters P, Lebwohl M, Hecker D, Kraus S, Baldwin H, Shalita A, Draelos Z, Markou M, Thiboutot D, Rapaport M, Kang S, Kelly T, Pariser D, Webster G, Hordinsky M, Rietschel R, Katz H, Terranella L, Best S, Round E, Waldstreicher J (1999). Finasteride in the treatment of men with frontal male pattern hair loss.. J Am Acad Dermatol 40 (6 Pt 1): 930-7. PMID 10365924.
  9. Ara, I.; Perez-Gomez, J.; Vicente-Rodriguez, G.; Chavarren, J.; Dorado, C.; Calbet, J. A. L. (2006). Serum free testosterone, leptin and soluble leptin receptor changes in a 6-week strength-training programme.. British Journal of Nutrition 96 (6): 1053-9.
  10. Habib F, Ross M, Ho C, Lyons V, Chapman K (2005). Serenoa repens (Permixon) inhibits the 5alpha-reductase activity of human prostate cancer cell lines without interfering with PSA expression.. Int J Cancer 114 (2): 190-4. PMID 15543614.
  11. Prager N, Bickett K, French N, Marcovici G (2002). A randomized, double-blind, placebo-controlled trial to determine the effectiveness of botanically derived inhibitors of 5-alpha-reductase in the treatment of androgenetic alopecia.. J Altern Complement Med 8 (2): 143-52. PMID 12006122.
  12. Marks L, Hess D, Dorey F, Luz Macairan M, Cruz Santos P, Tyler V (2001). Tissue effects of saw palmetto and finasteride: use of biopsy cores for in situ quantification of prostatic androgens.. Urology 57 (5): 999-1005. PMID 11337315.
  13. Iehlé C, Délos S, Guirou O, Tate R, Raynaud J, Martin P (1995). Human prostatic steroid 5 alpha-reductase isoforms — a comparative study of selective inhibitors.. J Steroid Biochem Mol Biol 54 (5-6): 273-9. PMID 7577710.
  14. includeonly>"Curis and Procter & Gamble Enter into R&D Agreement for Hair Growth Program". Retrieved on 2006-08-24.
  15. Hillmer A, Hanneken S, Ritzmann S, Becker T, Freudenberg J, Brockschmidt F, Flaquer A, Freudenberg-Hua Y, Jamra R, Metzen C, Heyn U, Schweiger N, Betz R, Blaumeiser B, Hampe J, Schreiber S, Schulze T, Hennies H, Schumacher J, Propping P, Ruzicka T, Cichon S, Wienker T, Kruse R, Nothen M (2005). Genetic variation in the human androgen receptor gene is the major determinant of common early-onset androgenetic alopecia.. Am J Hum Genet 77 (1): 140-8. PMID 15902657.
  16. Chumlea W, Rhodes T, Girman C, Johnson-Levonas A, Lilly F, Wu R, Guo S (2004). Family history and risk of hair loss.. Dermatology 209 (1): 33-9. PMID 15237265.
  17. Genetics of Pattern Baldness
  18. Christiansen K (1993). Sex hormone-related variations of cognitive performance in !Kung San hunter-gatherers of Namibia.. Neuropsychobiology 27 (2): 97-107. PMID 8515835.
  19. Schmidt J (1994). Hormonal basis of male and female androgenic alopecia: clinical relevance.. Skin Pharmacol 7 (1-2): 61-6. PMID 8003325.
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