Causes of Hair Loss in Men
By extreme the most conjoint cause of hair loss in men is androgenetic alopecia, also referred to as “male pattern” or “common” baldness. It is initiated by the effects of the male hormone dihydrotestosterone (DHT) on genetically inclined scalp hair follicles. This warmth to DHT is present primarily in hair follicles that exist in in the front, top, and crown of the scalp making a characteristic and easily recognizable pattern termed by Norwood.
It is repeatedly stated that “hair loss comes from the mother’s side of the family.” The truth is that baldness can be inherited from both sided. However, recent research suggests that the reasons for hair loss and balding may be a bit more complex than originally thought. Factors on the X-chromosome have been shown to influence hair loss, making the inheritance from the maternal side of the family slightly more important than the paternal one.
The identification of an androgen receptor gene on the X-chromosome helps to explain why the hair loss pattern of a man look like his maternal grandfather more often than his father. However, this is clearly not the whole story since a direct inheritance of baldness from the father is observed as well. An autosomal (non-sex) linked gene would explain this type of broadcast – but this gene has not yet been found.
DHT is shaped by the action of the enzyme 5-alpha reductase on testosterone, the hormone that bases sex characteristics in men. DHT causes male hair loss by restriction the growth, or anagen, phase of the hair cycle, causing shrinking of the follicles, and producing increasingly shorter, finer hairs. Eventually these hairs totally disappear.
In the patient below, we see a close-up of the side of his scalp where the hair is not affected by DHT. We see mostly groups of full thickness hairs (called terminal hairs) and a few scattered fine, vellus hairs. This is normal.
In the area of thinning (see circle below), we see that most of the hair has been miniaturized, although all of the hair is still present.
In the region that is balding (second circle in the center), there is extensive miniaturization and some, but not all of the hair has disappeared.
What this shows is that the preliminary appearance of hairless is due to the progressive decrease in hair shaft size, rather than the actual loss of hair – in early hair loss, all the hair is still present. This is the reason why hair loss drugs, such as finasteride (Propecia) work in early hair loss but don’t work in areas that are totally bald. It is also the reason why men’s hair transplant surgery, if not planned properly, can result in hair loss due to the shedding of nearby miniaturized hair.
Androgenetic hair loss is triggered by three inter-reliant factors: genes, hormones, and age:
Common baldness cannot happen without the presence of specific hereditary genes. These genes can be passed on by either parent. A gene is a single bit of chemically encoded hereditary instruction that is located on a chromosome and actually represents a tiny segment of DNA. Chromosomes occur in pairs (humans have 23 pairs), and every individual gets one set of chromosomes from each parent. Hair loss in men is now felt to involve more than one gene. When several genes govern a trait, it is called polygenic.
Genes that are located on the X or Y-chromosomes are call sex-linked. Genes on the other 22 pairs of chromosomes are called autosomal. It is felt that the genes governing common baldness are autosomal . This means that the baldness trait can be inherited from the mother’s side of the family or the father’s side with equal frequency. The commonly held notion that baldness comes only from the mother’s side of the family is incorrect, although for reasons not fully understood, the predisposition inherited from an affected mother is of slightly greater importance than that inherited from an affected father.
The term, “dominant” means that only one gene of a pair is needed for the trait to show up in the individual. A “recessive” gene means that both genes need to be present in order for the trait to be expressed. The genes involved in balding from androgenetic alopecia are felt to be dominant.
Just because one has the genes for baldness, it doesn’t mean the trait will manifest itself. The ability of a gene to affect one’s characteristics, i.e. be visible in a particular individual, is called “expressivity”. Gene expression is related to a number of factors, the major ones being hormones and age, although stress and other factors can be reasons for hair loss and balding in some individuals.
It is of interest that, although genes for some types of male hair loss have been mapped, none of the genes for male pattern baldness have yet been identified. This suggests that any kind of genetic engineering to prevent common baldness is still many years away.
Hormones are biochemical substances that are made in several glands throughout the body. These glands hide their products right into the bloodstream so that the organic they make is binge throughout the body. These chemicals are very powerful so that only minute amounts of them have reflective effects upon the body.
The major male sex hormone is called testosterone. Testosterone and other related hormones that have masculinizing belongings are made mainly in the testicles; therefore, the hormonal levels that are seen in adults do not reached significant levels until the testicles develop and increase during adolescence. In fact, these same hormones are the cause of many of the changes that occur in puberty; growth of phallus and scrotum, sperm production, development of a sex drive, change in the voice, growth of axillary and pubic hair, development of an adult odor in the sweat, increase in bone and muscle mass, and change in the basic body shape.
The existence of the necessary genes and hormones is not alone adequate to cause baldness. Even after a person has reached puberty, liable hair follicles must continually be uncovered to the hormone over a period of time for hair loss to occur. The age at which these effects finally visible themselves varies from one individual to another and is related to a person’s genetic composition and to the levels of testosterone in the bloodstream.
There is another time reason that is off-color understood. Male hair loss does not occur all at once nor in a steady, straight-line progression. Hair loss is characteristically cyclical. People who are losing their hair experience flashing periods of slow and rapid hair loss and even stability. Many of the reasons that hair loss rates speed up and speed down are unknown, but we do know that with age, a person’s total hair volume will decrease.