Each hair consists of several parts:
- The stem of hair – this is the part of hair which is on the epidermis surface, it consists of cellular structure full of keratin;
- Hair bulb – this component is about 2,5 mm deep in skin and consists of live cells, which can constantly multiply and grow.
So, the hair bulbs define the hair condition and hair growing process as well.
However, cellular structures cannot multiply, hair bulb forms the part of the hair together with nearby tissues, which is called hair bag – follicle. Follicles are surrounded by blood vessels and nerve ending.
It is interesting that the form of follicle defines the appearance of hair:
- Wavy hair develops from oval follicles
- Straight hair grows from round follicles
- Curly hair appears from follicles with the shape of kidney.
Hair bag has a great importance for hair growth and heath. If it is injured, after the death of hair end, it is impossible to restore it. Fat glands near the hair follicle are also of a great importance for hair condition and beauty. Secretion of fat glands has antibacterial and protecting function. The lack of it causes desquamation and dry skin, and in case of its excess skin becomes too oily and glossy.
Healthy hair follicles provide fast hair growth as well as its long cycle.
Separate hairs on our head grow for about 2-8 years. This period can be longer (4-8 years) in women than in men (2-6years). Each hair follicle is genetically programmed to form 25-27 hair.
The growth cycle of a hair consists of 3 stages:
- Anagen – Active growing stage.
- Catagen – Intermediate stage.
- Telogen – Shedding stage.
Each hair has its individual “growth plan”. That’s why different hairs are on different stages od hair growth cycle at the same time, more exactly: 85% - in Anagen, 1% - in Catagen, 14 % - in Telogen.
Active growth period typically lasts about 3-6 years. New cells are formed in hair follicle matrix, they reach to the skin surface of hairy part of head and create anagenic hairs.
The cells in hair follicle matrix multiply and start shedding step by step. Hair follicle turns into so called “resting condition”. Hair bulb starts shedding from the hair papilla. Catagen is a very short stage lasting for about 2-4 weeks.
Being separated from dermal papilla, Telogenic bulb forms becomes elongated in shape and moves to skin surface. In Telogen stage older hairs fall and new ones start to grow. During that period cell renewal in follicles is stopped. (for about 3 month). Newly formed hair follicle joins the hair papilla and a new hair starts its Anagen stage.
On average, each person has 100-150 hair follicles on hairy part of head. Hairs develop, grow and shed in them. Being aware of hair growth cycle enables us to calculate normal number of daily hair loss (50-100 hairs).
The hormones, involved in androgenic hair loss mechanism, are male hormones called androgens. The answer to the question – “How do androgens cause hair loss?” - is not clear enough. They can make a deep effect on different biological mechanisms of a body. Like other hormones, they can also contact with cells and cell membrane receptors. Some androgens affect hair follicles, and different type and location follicles respond differently to the same androgens. For example: In respond to androgens armpit hair start growing, but scalp hair start falling.
Male Hair Loss
Mainly two types of androgens are involved in males hair loss, they are testosterone and
dihydrotestosterone (DHT hormone). Dihydrotestosterone is formed from testosterone. The enzyme- 5-alpha reductase turns inactive testosterone into a more power form
which is called dihydrotestosterone. So 5-alpha reductase is the key enzyme involved in androgenetic hair loss, which is also discovered in the skin around hair follicle – in papillary dermis. Having been turned into more active hormone, DHT is capable to contact with all the type of androgenic receptors of hair follicle.
As a result of the influence made by these two hormones and their receptors in hair follicles, changes start to occur in scalp hair, which lead to hair loss. Terminal hair growing phase on scalp is becoming progressively shorter with time, Anagen phase (growing) is shortened. The duration of Catagen (intermediate) and Telogen (resting) phases remains the same, which leads to the final result – increasing the number of hairs being in resting phase. Accordingly, we get Telogen follicles increase up to 20% (10% is a norm). Thus, more hair is in resting phase. Damaged hairs are reduced in size and diameter. Hair becomes thinner, shorter and less dark in color. Such hairs fall with time and their follicles are drained.
There may arise a question: “Why do some men have hair loss and others don’t, when all of the male and female bodies include these hormones and their receptors?” A perfect satisfactory answer to that doesn’t exist, however there are several theories discussed below:
- In patients with androgenetic hair loss, each follicle on the bald area of scalp has more than normal number of androgenic receptors. So, the androgens being in norm in the blood affect more harmfully as if their amount is above the norm.
- In bald people hair follicle receptors have much higher sensitivity, which intensifies the influence of androgens (hair loss).
- The enzyme 5-alpha reductase is higher in the balding area, which converts more testosterone to dihydrotestosterone. The higher the proportion of the DHT hormone to testosterone, the faster the hair loss process.
Male hormones influence on genetically predisposed hair follicles is the reason of androgenic alopecia. The male hormones causing hair loss are called androgens; this is where the name of this type of hair loss comes from _ “Androgenic Alopecia”. There are three important factors influencing on hair loss during androgenic alopecia. There factors are tightly connected with each other.
Hair loss happens during androgenic alopecia, only in case if a woman or man has a certain genetic code in chromosomes. This genetic code is responsible for alopecia and it can include one gene or a combination of genes, as well as there is possibility to inherit it from mother or father.
According to a popular explanation of inherited androgenic alopecia, the gene causing alopecia is inherited to sons from mothers. Genetic analysis of chromosomes of the parents, having androgenic alopecia, showed that this approach was wrong in two aspects. On the one hand, androgenic hair loss is inherited in an autosomal dominant way, so the gene causing hair loss can be inherited from both parents. On the other hand, this gene can be found in women as well as men, so children of both sex can have androgenic alopecia.
One more important fact, which should be mentioned, is that not all people having this gene develop alopecia. In order the gene to be active, it should be expressed in an individual. The certain gene can be expressed based on several facts like hormones, age, stress, etc. In conclusion, if a person doesn’t have androgenic hair loss, the reason can be absence of this hormone or it is not expressed.
The definite gene (genes), causing androgenic hair loss, still is not identified. However, scientists believe that this gene (genes) is responsible for synthesis of male hormones 5 alpha reductase androgenic receptors, which are located in hair follicles. There are three main factors in developing if androgenic alopecia: 5 alpha reductase is the ferment which transfoms testosterone (male sex hormone) into more active form dihydrotestosterone (DHT), which is connected to the androgenic receptors existing in hair follicles.
Thanks to the big achievements in genetic engineering and genetic medicine field, in near future scientists will be able to identify the gene (genes) responsible for androgenic hair loss. This will help us not only to treat androgenic alopecia, but to predict hair loss right from birth.
Hair Loss Caused by Age
It is important to know that having both factors – genetic predisposition and excess hormone, is not enough to start androgenic hair loss. The process takes certain time, when hormone sensitive follicles start obeying to male hormone influence. The time needed for the described process above is varied and differs in individual case. Male type hair loss depends on the expressed genetic predisposition and androgen concentration in blood.
However, even in case when there is no genetic predisposition for hair loss, some hairs suddenly decrease in length and diameter alongside with age. The process is called hair miniaturization. As a result, miniaturized hairs start disappearing and the number of follicles is decreasing.
There are several forms of hair loss. Some of them are much more serious than others, some need medical interference. Telogen Effluvium – telogenic hair disappearance, is one of the common forms of hair loss.
The condition is connected to stress and isn’t permanent. Hair stops growing process before falling. After about 3 months from this condition hair falls. Unlike more severe forms of hair loss, hair starts growing again for the next 6-9 month.
Alopecia Areata is also a type of hair loss caused by stress. In that case, white blood cells fight against hair follicles and this leads to fast hair loss. Hair loss frequently develops limited in one or several areas, although it can cover the whole scalp for several weeks, in rare cases hair loss can be developed on the body too. Hair often starts growing again, but not always. In some cases it needs treatment.
The most common hair loss type caused by stress is Telogen Effluvium. In case of such hair loss, hairs stop growing and turn into resting condition, after 2-3 month they fall and 6-9 month later start growing again.
If your hair is getting thinner or you have a hair loss issue, an appointment with a doctor is recommended for you in order to solve the problem. This can be a natural aging process of a body, however if you are a youngster, or 20-30 years old, or your hair loss seems irregular and abnormal, a serious problem can occur.
In a lot of cases stress is the main cause of hair loss. Stress isn’t a new phenomenon, it has always been a part of a human life, although due to the modern medical achievements, we can easily see how destructive it can appear for a human body. The obligations of modern life doesn’t help to solve this problem at all and if you think that stress is the reason of your hair loss, we advise you to reconsider your lifestyle in order to realize how to take control over your stress level. Our lifestyle plays an important part on our wellbeing, accordingly our hair isn’t an exception, it is also greatly affected by stress.