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    Male Pattern Baldness (Hair Loss) and Genetics
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    Background Information

    Definition

    Male Pattern Baldness is the most common form of baldness and involves progressive hair thinning, mostly occurs in adult male humans.

    Introduction

    The 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, Victoria, Australia showed the prevalence of mid-frontal hair loss increases with age and affects 73.5% of men and 57% of woman aged 80 and over. According to Medem Medical Library's website, male pattern baldness (MPB) affects roughly 40 million men in the United States. Approximately 25 percent of men begin balding by age 20; two-thirds begin balding by age 60. There is a 4 in 7 chance of getting the baldness gene.

    Male pattern is characterized by hair receding from the lateral sides of the forehead, known as a "receding hairline". Receding hairlines are usually seen in males above the ages of 20 but can be seen as early as late teens as well.

    Male pattern baldness is mostly the result of a genetic event that causes dihydrotestosterone (DHT), a male hormone, to cause the hair follicles to shrivel. The hair produced is progressively smaller, until it is practically invisible (or may disappear completely). It has been speculated that this is an evolutionary event that signifies maturity and conveys greater authority on affected men.

    The mechanism by which DHT accomplishes this is not yet fully 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. Male pattern baldness is classified on the Hamilton-Norwood scale I-VII.

    It was previously believed that baldness was inherited from the maternal grandfather. 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".

    Male Pattern Baldness and Genetics

    Much research went into the genetic component of male pattern baldness, or androgenetic alopecia (AGA). Research indicates that susceptibility to premature male pattern baldness is largely X-linked. Other genes that are not sex linked are also involved.

    German researchers name the androgen receptor gene as the cardinal prerequisite for balding. They conclude that a certain variant of the androgen receptor is needed for AGA to develop. In the same year the results of this study were confirmed by other researchers. This gene is recessive and a female would need two X chromosomes with the defect to show typical male pattern alopecia. Seeing that androgens and their interaction with the androgen receptor are the cause of AGA it seems logical that the androgen receptor gene plays an important part in its development.

    Other research in 2007 suggests another gene on the X chromosome, that lies close to the androgen receptor gene, is an important gene in male pattern baldness. They found the region Xq11-q12 on the X-chromosome to be strongly associated with AGA in males. They point at the EDA2R gene as the gene that is mostly associated with AGA. This finding has been replicated in at least three following independent studies.

    Other genes involved with hair loss have been found. One of them being a gene on chromosome 3. The gene is located at 3q26. This gene is also involved in a type of baldness associated with mental retardation. This gene is recessive .

    Another gene that might be involved in hair loss is the P2RY5. This gene is linked to hair structure. Certain variants can lead to baldness at birth while another variant causes "wooly hair".

    Recent research confirmed the X linked androgen receptor as the most important gene. With a gene on chromosome 20 being the second most important determinant gene (snpedia)

    Hair Loss Treatment

    While many people with male pattern baldness choose to accept the condition as they accepted their hair color or shape, there are baldness treatments which can reduce or halt hair loss, and in early stages or in many cases, temporarily reverse it entirely.

    Baldness treatments are estimated to be a US $1 billion per year industry. Slightly less than half of men experience male pattern baldness (MPB) by age 50, Since the 1980s, drug therapy has increasingly become a realistic management option for baldness in men. Increased understanding of the role of the hormone dihydrotestosterone (DHT) in male and female pattern baldness has led to targeted intervention to prevent this hormone from acting on receptors in the scalp.

    However, experts warn that many treatments marketed as hair loss cures are ineffective aside from the placebo effect.

    Hair transplantation is a surgical technique that involves moving individual hair follicles from one part of the body (the donor site) to bald or balding parts (the recipient site). It is primarily used to treat male pattern baldness, whereby grafts containing hair follicles that are genetically resistant to balding are transplanted to bald scalp. However, it is also used to restore eyelashes, eyebrows, beard hair, chest hair, and pubic hair and to fill in scars caused by accidents or surgery such as face-lifts and previous hair transplants. Hair transplantation differs from skin grafting in that grafts contain almost all of the epidermis and dermis surrounding the hair follicle, and many tiny grafts are transplanted rather than a single strip of skin.

    For more information and reference: http://en.wikipedia.org/wiki/Baldness

    Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License and Creative Commons Attribution-ShareAlike License.)

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