One form of hair loss in both men and women is known as alopecia androgenetica>
One common form of hair decline in both men and women is known as alopecia androgenetica (also known as androgenetic alopecia or androgenic alopecia). In men in particular this condition is also commonly known as male pattern baldness. Well defined patterns of hair loss start to occur above both temples. Thinning of hair also occurs at the wreath of the head. Most of the time a rim of hair around the sides and rear of the head is left but the condition can lead to complete baldness.
Male pattern baldness is most often seen in men above the ages of 20 but can be seen as early as late teens as well. Male pattern baldness is caused by DHT a powerful sexual urge hormone body and facial hair growth promoter that can adversely affect the prostate as well as the hair located on the head. The genetic predisposition of hair follicles to DHT causes them to shrink when exposed to it. This shortens the lifespan of hair follicles and prevents males from producing hair normally which is characterized by hair receding from the lateral sides of the forehead known as a receding hairline. An additional bald patch may develop on the top of the head as well.
It is very rare for alopecia androgenetica in females to lead to complete baldness. What is different about alopecia androgenetica in females than in males is that with females the hair thins out all over the head and there is no receding hair line. This causes the hair to look patchy and can greatly affect a females self esteem.
A range of genetic and environmental factors are likely to play a role in causing androgenic alopecia and although researchers are studying all the factors that may contribute to this condition though most of these are still unknown. Researchers are resolute though, that this form of hair loss is related to hormones called androgens. They are paying particular attention to an androgen called dihydrotestosterone (DHT). Androgens are important for normal male sexual development before birth and during puberty. Androgens also have other important functions in both males and females such as regulating hair growth and sex mechanism.
Incidences of alopecia androgenetica vary from population to population and based on genetical background information environmental factors do not seem to affect this type of baldness greatly. One large scale of measurement study in Maryborough 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. According to Medem Medical Library, male pattern baldness affects roughly 40 million men in the United States of America and approximately 25 percent of these men start going bald by age 30 and 65 percent of men go bald by age 60. Overall there is a 60 percent chance of a male human going bald. It is not yet fully understood how DHT accomplishes such a high percentage of hair loss.
In hair loss prone scalps DHT initiates a summons of follicular miniaturization. Through this process of follicular miniaturization the hair shaft width is progressively decreased until scalp hair resembles fragile vellus hair or else becomes non existent. Onset of alopecia androgenetica sometimes begins as early as end of puberty and is mostly genetically determined. It was previously believed that alopecia androgenetica was inherited from the maternal grandfather but now there is some basis for the belief both parents contribute to the likelihood of hair loss in their offspring. Most likely heritage is technically autosomal dominant with mixed penetrance.