(AGA) or Common
Alopecia is understood as a reduction in hair density or lack of hair, in a specific affected area or widespread over the scalp, that is temporary or permanent. Many disorders present with signs of alopecia. The most frequent types of alopecia are:
Androgenic alopecia or common baldness, as its name indicates, is due to the genetic predisposition of an individual (although the genes involved are still not completely described).
That is, there has to be a special follicular sensitivity to circulating androgens and a certain degree of penetration into the hair follicle. It is one of the most common forms of alopecia in men and women.
In the follicles, the enzyme 5α-reductase converts the free testosterone to 5α-dihydrotestosterone (5-DHT). This triggers a series of processes that lead to the phenomenon of follicle miniaturisation and hair thinning. In other words, the growth phase in each cycle gets progressively shorter while the latency/resting phase gets longer; vellus hair replaces the terminal type and causes an apparent lack of hair. If this process is not properly treated, this process gradually evolves to irreversible alopecia.
As we have indicated, it affects both sexes, although with different clinical symptoms.
Male androgenetic alopecia (MAGA)
In Spain, 63% of 50-year-old men present MAGA, a proportion that increases with age. The distribution of the hair loss produced follows recognised clinical patterns divided into several degrees of severity.
The Spanish Trichology Group of the Spanish Academy of Dermatology and Venereology (AEDV) decided to adopt the Ebling scale.
Female androgenetic alopecia (FAGA)
In Spain, 36% of women suffer from female pattern androgenetic alopecia (FAGA), which usually becomes more accentuated after menopause, from the loss of estrogen protection. In the majority of cases there is a family history, although some factors can aggravate the tendency towards alopecia; an example is the iron deficiency that is the factor most frequently involved.The hair loss pattern in women with FAGA is different from that of men. It begins with a diffuse «crown» hair loss respecting the frontal hairline.
Telogen alopecia is a type in which, for specific and varying causes, the evolution of the follicles from anagen to telogen phases accelerates, with consequent abundant hair loss at 2-4 months.
Its duration is variable, but there is complete hair recovery with the same growth pattern as before the alopecia.
Some common causes are stress, acute anxiety or depression, biotin and zinc deficiencies, low-calorie diets, the postpartum period, prolonged fever, extensive surgery and anaesthesia, dermatosis such as psoriasis, consumption of certain drugs (selenium, lithium, oral contraceptives, anticoagulants, β-blockers) and ultraviolet radiation (exposure to sunlight).
In this type of alopecia, the causes or stimuli act directly on the follicles in the anagen phase, provoking hair loss that occurs almost immediately or shortly after the cause.
Its origin can be diseases (for example, hypothyroidism and hyperthyroidism), deficiencies in zinc or essential fatty acids; from anti-cancer drugs, mycotic and bacterial infections and excessive use of harsh chemical agents (hydrogen peroxide and thyoglycolate used in hairdressing); and it can also be caused by the compulsion to pull hair out of the scalp (trichotillomania), by scratching the scalp and by overly energetic hair brushing.
Alopecia areata is a benign self-limiting autoimmune disorder characterised by the presence of alopecic or hairless areas. Starting with genetic predisposition (15%-20% of the patients have family histories), environmental factors seem to be important; for example, psychosocial stress can trigger the outbreak.
Clinical symptoms can range from a single limited alopecic patch (generally on the scalp) up to complete baldness, known as total alopecia, and even to all the hairy areas of the body, universal alopecia.
Its evolution and prognosis are unpredictable. The hair may grow back again, and it is fine and colourless at the beginning, recovering its texture and colour in a short while.
Although it is a benign condition medically, it can have strong negative repercussions on the quality of life of the patients and their functional capacity.