Diffuse hair loss is one of the most common reasons for patients to visit a dermatologist and dermatocosmetologist, as well as a source of quite serious stress and social exclusion. The patient's anxiety grows in direct proportion to his previous experience with specialists, when, in his opinion, the doctors did not take the problem of thinning his hair seriously enough.
Ekaterina Alekseevna Bardova
candidate of medical sciences
dermatovenereologist, cosmetologist,
associate professor of the department of dermatovenereology NMAPO named after. P.L. Shupika
Hair growth cycle
The hair follicle is in a state of constant renewal during continuous cycles that replace each other - proliferation (anagen), involution (catagen), rest (telogen). The main feature of telogen is that in this phase not only the hair shaft grows, but the proliferation of most of the epithelial sections of the hair follicle occurs. In the catagen phase, hair follicles begin the process of involution, which is characterized by the activation of programmed cell death in follicular keratinocytes, as a result of which the hair moves upward. In the telogen phase, the hair shaft transforms into an atrophied hair, anchored at the base of the follicular epithelium until it actually falls out.
Cyclical hair growth occurs randomly, with each follicle having its own mechanism for controlling development and initiating successive phases, although it is also influenced by factors such as hormones, cytokines, growth factors, and environmental factors such as toxins, medicines, lack of minerals and vitamins.
On the scalp, hairs in the anagen phase last for 2-6 years, the duration of telogen is 100 days, resulting in a ratio of hairs in these phases of 9:1. On average, the number of newly formed hairs corresponds to the number of hairs that have fallen out, thereby maintaining the constancy of the hairline. The average daily amount of hair shed should be 50-100 hairs, with a peak number of hairs in the telogen phase by the end of summer.
Possible causes of pathological hair loss
Many factors can lead to pathological hair loss. Violation of the dynamics of hair growth may be associated with a violation of the cycle of their growth. So, for example, dystrophic anagen alopecia occurs as a result of the loss of a large amount of hair in the growth phase, due to direct damage to the cells of the matrix of the hair follicle bulb. At the same time, telogen effluvium occurs when a large amount of hair that is in the telogen phase falls out.
Among the causes of hair loss, a significant role is played by the use of various medications. In this case, hair loss may not be observed immediately, but after a few weeks or months after the start of taking the drug, or it may begin (or become) more pronounced after its withdrawal. Usually, with prolonged use of one or another drug, diffuse alopecia develops, and almost exclusively the scalp is involved in the pathological process. Only in extremely rare cases, the development of universal alopecia is possible, which, in particular, is observed when taking cytotoxic drugs, for example, used when the patient has a malignant tumor process, as well as provoked by radiation.
Alopecia can be triggered by medications
The mechanism of development of alopecia due to the intake of any medicinal substances is currently not completely clear. It is assumed that it is based on the interaction of active substances of medicinal substances with follicular keratinocytes, hair matrix cells, as well as connective tissue cells surrounding the hair follicle and perifollicular blood vessels. The keratinocytes of the hair follicles are the most frequently targeted for the toxic effects of drugs.
In addition, hair follicle keratinocytes have a pronounced ability (much greater than epidermal keratinocytes) to metabolize various substances, primarily of an exogenous nature.
However, the same chemical compound (drug) does not in all cases cause the development of alopecia, and its severity is not always the same. It is possible that this is due to the peculiarities of the interaction between endogenous and exogenous factors.
Diffuse alopecia due to drug exposure usually does not develop suddenly, but within a few months after a certain latent period. During this period, there is a gradual decrease in the diameter of the hair follicle, a slowdown in the rate of hair growth. Dystrophic changes in the hair shaft develop due to a violation of protein biosynthesis, a characteristic feature of which is the presence of a pointed tip in growing hair (like a writing pen). When analyzing the trichogram in such patients, there is a significant increase in the number of hairs, the follicles of which are in the telogen phase (30% or more). However, to make a differential diagnosis between diffuse alopecia induced by drug exposure to the hair papilla, and idiopathic anagen or telogen hair loss is very difficult, since trichogram and histological findings are nonspecific. In these cases, the anamnesis contributes to the correct diagnosis. In addition, recurrence of hair loss with repeated prescription of a drug that is suspected to be the etiological factor can help to make a correct diagnosis.
Medicines that can cause hair loss
Drugs that can lead to hair loss are widely used in the clinical practice of dermatologists, cardiologists, gynecologists, internists, psychiatrists and other doctors. In general, alopecia can result from the use of any drug.
But it was found that most often increased hair loss is observed while taking the following groups of drugs:
- vitamin A and its derivatives;
- beta-adrenergic blockers (selective and non-selective);
- angiotensin-converting enzyme blockers;
- antibacterial drugs;
- non-steroidal anti-inflammatory drugs;
- anticoagulants;
- 6-aminoquinoline derivatives;
- thyrostatic drugs;
- histamine H2 receptor blockers;
- non-steroidal antiestrogens;
- a-interferon preparations;
- imidazole derivatives;
- antidepressants;
- anticonvulsants;
- antipsychotics;
- antiparkinsonian drugs;
- hydroxychloroquine derivatives;
- triazole derivatives;
- ketoconazole;
- uricostatic drugs;
- uricosuric drugs;
- oral contraceptives;
- cytostatics;
- anthelmintic drugs;
- lithium preparations;
- antiherpetic drugs;
- dopaminomimetics (bromocriptine);
- depilatories (especially if they are often used on diseased surfaces);
- boric acid.
At the same time, it was noted that of the above drugs, diffuse alopecia develops much more often under the influence of anticonvulsants, antidepressants, neuroleptics, vitamin A and its synthetic derivatives, cytostatics, b-blockers.
So, cytostatic drugs, especially when administered in large doses, lead to an almost complete cessation of mitotic division of hair follicle cells.
Antibiotics, antiherpetic and other agents can disrupt the matrix-papilla bond, which drastically shortens the duration of the anagen phase and, consequently, the hair passes into the catagen phase and then into the telogen phase much faster than normal, which leads to their intense loss. In some cases, hair follicles do not enter the catagen and telogen phases, and the hair falls out in the anagen phase. This mechanism, which causes the development of a condition called anagen hair loss, has been well established for anticoagulants, preparations containing lithium and boric acid. With the help of light microscopy, according to certain signs (the length of the root of the hair, the presence of internal and external root sheaths, the presence or absence of pigment in the area of the hair bulb, etc.), it is possible to determine
Oral contraceptives reduce the duration of the growth phase (anagen phase). In addition, oral contraceptives help reduce the concentration of vitamin B12 in the blood serum, which also worsens the condition of the hair.There are reports in the literature that hair loss can be caused by the use of nicotinic acid. On the one hand, this drug has a pronounced vasodilating effect, on the other hand, it helps to lower blood cholesterol levels.
Cholesterol is known to be one of the main lipids found in the dermis and therefore in the hair papilla. It is possible that changes in the process of keratinization also occur, but so far the mechanism of action of nicotinic acid on hair growth has not been elucidated. According to the observations of many scientists, nicotinic acid and its derivatives (xanthinol nicotinate, teonikol), prescribed in short courses (1-1.5 months) and in small doses (0.15-0.3 g per day, depending on age) in order to stimulate blood circulation in the vessels of the dermis with various pathologies of the hair, do not cause hair loss.
Taking certain drugs can cause excessive hair growth - initially vellus, which over time transforms into coarse. This effect, which is most often pronounced in cases where the drug is prescribed in large doses and for a long time, is probably due to a faster transition from the telogen phase to the anagen phase. These include: corticosteroids, minoxidil, cyclosporine A, D-penicillamine, diphenylhydantoin, psoralen.
The side effect of these drugs made it possible to treat some forms of alopecia, but the effect achieved in the vast majority of cases is unstable, the disease recurs on average three to four months after stopping treatment.
In most cases, hair loss caused by the use of this or that drug is reversible. As a rule, hair regrowth is observed several months after the cessation of exposure to the etiological factor and depends on the severity of changes in the hair follicle.
Source estet-portal.com
Share:
Add a comment