living hair matrixes. long-term of insufficiency of nutrition is an important cause for the death of hair matrixes. misrepair-accumulation aging theory suggests that dermal fibrosis is associated with the progressive hair-loss and hair-whitening in old people. with age, the dermal layer of the skin has progressive deposition of collagen fibers, and this is a result of accumulation of misrepairs of derma. fibrosis makes the derma stiff and makes the tissue have increased resistance to the walls of blood vessels. the tissue resistance to arteries will lead to the reduction of blood supply to the local tissue including the papillas. dermal fibrosis is progressive; thus the insufficiency of nutrition to papillas is permanent. senile hair-loss and hair-whitening are partially a consequence of the fibrosis of the skin. diagnosis the diagnosis of androgenic alopecia can be usually established based on clinical presentation in men. in women, the diagnosis usually requires more complex diagnostic evaluation. further evaluation of the differential requires exclusion of other causes of hair loss, and assessing for the typical progressive hair loss pattern of androgenic alopecia. trichoscopy can be used for further evaluation. biopsy may be needed to exclude other causes of hair loss, and histology would demonstrate perifollicular fibrosis. the hamilton–norwood scale has been developed to grade androgenic alopecia in males by severity. treatment main article: management of hair loss androgen-dependent finasteride is a medication of the 5α-reductase inhibitors (5-aris) class. by inhibiting type ii 5-ar, finasteride prevents the conversion of testosterone to dihydrotestosterone in various tissues including the scalp. increased hair on the scalp can be seen within three months of starting finasteride treatment and longer-term studies have demonstrated increased hair on the scalp at 24 and 48 months with continued use. treatment with finasteride more effectively treats male-pattern hair loss at the crown than male-pattern hair loss at the front of the head and temples. dutasteride is a medication in the same class as finasteride but inhibits both type i and type ii 5-alpha reductase. dutasteride is approved for the treatment of male-pattern hair loss in korea and japan, but not in the united states. however, it is commonly used off-label to treat male-pattern hair loss. androgen-independent minoxidil dilates small blood vessels; it is not clear how this causes hair to grow. other treatments include tretinoin combined with minoxidil, ketoconazole shampoo, dermarolling (collagen induction therapy), spironolactone, alfatradiol, topilutamide (fluridil), topical melatonin, and intradermal and intramuscular botulinum toxin injections to the scalp. female pattern there is evidence supporting the use of minoxidil as a safe and effective treatment for female pattern hair loss, and there is no significant difference in efficiency between 2% and 5% formulations. finasteride was shown to be no more effective than placebo based on low-quality studies. the effectiveness of laser-based therapies is unclear. bicalutamide, an antiandrogen, is another option for the treatment of female pattern hair loss. procedures more advanced cases may be resistant or unresponsive to medical therapy and require hair transplantation. naturally occurring units of one to four hairs, called follicular units, are excised and moved to areas of hair restoration. these follicular units are surgically implanted in the scalp in close proximity and in large numbers. the grafts are obtained from either follicular unit transplantation (fut) or follicular unit extraction (fue). in the former, a strip of skin with follicular units is extracted and dissected into individual follicular unit grafts, and in the latter individual hairs are extracted manually or robotically. the surgeon then implants the grafts into small incisions, called recipient sites. cosmetic scalp tattoos can also mimic the appearance of a short, buzzed haircut. alternative therapies many people use unproven treatments. regarding female pattern alopecia, there is no evidence for vitamins, minerals, or other dietary supplements. as of 2008, there is little evidence to support the use of lasers to treat male-pattern hair loss. the same applies to special lights. dietary supplements are not typically recommended. a 2015 review found a growing number of papers in which plant extracts were studied but only one randomized controlled clinical trial, namely a study in 10 people of saw palmetto extract. prognosis androgenic alopecia is typically experienced as a "moderately stressful condition that diminishes body image satisfaction". however, although most men regard baldness as an unwanted and distressing experience, they usually are able to cope and retain integrity of personality. although baldness is not as common in women as in men, the psychological effects of hair loss tend to be much greater. typically, the frontal hairline is preserved, but the density of hair is decreased on all areas of the scalp. previously, it was believed to be caused by testosterone just as in male baldness, but most women who lose hair have normal testosterone levels. epidemiology female androgenic alopecia has become a growing problem that, according to the american academy of dermatology, affects around 30 million women in the united states. although hair loss in females normally occurs after the age of 50 or even later when it does not follow events like pregnancy, chronic illness, crash diets, and stress among others, it is now occurring at earlier ages with reported cases in women as young as 15 or 16. for male androgenic alopecia, by the age of 50 30-50% of men have it, hereditarily there is an 80% predisposition. notably, the link between androgenetic alopecia and metabolic syndrome is strongest in non-obese men. society and culture certain studies have suggested androgenic alopecia conveys survival advantage studies have been inconsistent across cultures regarding how balding men rate on the attraction scale. while a 2001 south korean study showed that most people rated balding men as less attractive, a 2002 survey of welsh women found that they rated bald and gray-haired men quite desirable. one of the proposed social theories for male pattern hair loss is that men who embraced complete baldness by shaving their heads subsequently signaled dominance, high social status, and/or longevity. biologists have hypothesized the larger sunlight-exposed area would allow more vitamin d to be synthesized, which might have been a "finely tuned mechanism to prevent prostate cancer" as the malignancy itself is also associated with higher levels of dht. myths an ancient phenomenon: greek philosophers with and without much hair (from left to right: socrates, antisthenes, chrysippus, and epicurus, fifth to third centuries bc) many myths exist regarding the possible causes of baldness and its relationship with one's virility, intelligence, ethnicity, job, social class, wealth, and many other characteristics. weight training and other types of physical activity cause baldness because it increases testosterone levels, many internet forums have put forward the idea that weight training and other forms of exercise increase hair loss in predisposed individuals. although scientific studies do support a correlation between exercise and testosterone, no direct study has found a link between exercise and baldness. however, a few have found a relationship between a sedentary life and baldness, suggesting exercise is causally relevant. the type or quantity of exercise may influence hair loss. testosterone levels are not a good marker of baldness, and many studies actually show paradoxical low testosterone in balding persons, although research on the implications is limited. baldness can be caused by emotional stress, sleep deprivation, etc. emotional stress has been shown to accelerate baldness in genetically susceptible individuals. stress due to sleep deprivation in military recruits lowered testosterone levels, but is not noted to have affected shbg. thus, stress due to sleep deprivation in fit males is unlikely to elevate dht, which is one cause of male pattern baldness. whether sleep deprivation 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 dht levels, but unless free testosterone is virtually nonexistent, 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 not the only determining factor in baldness. additionally, because hair loss is progressive and free testosterone declines with age, a male's hairline may be more indicative of his past than his present disposition. frequent ejaculation causes baldness many misconceptions exist about what can help prevent hair loss, one of these being that lack of sexual activity will automatically prevent hair loss. while a proven direct correlation exists between increased frequency of ejaculation and increased levels of dht, as shown in a recent study by harvard medical school, the study suggests that ejaculation frequency may be a sign, rather than a cause, of higher dht levels. another study shows that although sexual arousal and masturbation-induced orgasm increase testosterone concentration around orgasm, they reduce testosterone concentration on average, and because about 5% of testosterone is converted to dht, ejaculation does not elevate dht levels. the only published study to test correlation between ejaculation frequency and baldness was probably large enough to detect an association (1,390 subjects) and found no correlation, although persons with only vertex androgenetic alopecia had fewer female sexual partners than those of other androgenetic alopecia categories (such as frontal or both frontal and vertex). one study may not be enough, especially in baldness, where there is a complex with age. other animals animal models of androgenic alopecia occur naturally and have been developed in transgenic mice; chimpanzees (pan troglodytes); bald uakaris (cacajao rubicundus); and stump-tailed macaques (macaca speciosa and m. arctoides). of these, macaques have demonstrated the greatest incidence and most prominent degrees of hair loss. baldness is not a trait unique to human beings. one possible case study is about a maneless male lion in the tsavo area. the tsavo lion prides are unique in that they frequently have only a single male lion with usually seven or eight adult females, as opposed to four females in other lion prides. male lions may have heightened levels of testosterone, which could explain their reputation for aggression and dominance, indicating that lack of mane may at one time have had an alpha correlation. although primates do not go bald, their hairlines do undergo recession. in infancy the hairline starts at the top of the supraorbital ridge, but slowly recedes after puberty to create the appearance of a small forehead.