Head hair grows according to the physiological cycle. This cycle consists of three phases – anagen, catagen and telogen. Anagen is a growth phase that lasts about 2 to 6 years; at this time, the average rate of hair extension is 1 cm per month. After the growth phase, there is a transitory phase, called catagen. Catagen lasts about two weeks and then the hair stops growing. The last phase, called telogen, lasts from 2 to 6 months and boils down to the loss of an old hair and the creation of a new hair in its place.
This cycle does not synchronize all hairs, which results in gradual and balanced hair exchange. About 90% of hair is in the growth phase, and only 10% – in the phase of falling out. Around 100 hairs fall out each day. When more hair falls out for a long time – the hairstyle is thinning and we talk about excessive hair loss or even baldness.
Telogen effluvium – a common cause of hair loss
Telogen effluvium is an excessive hair loss resulting from the transition to the resting phase of most hair on the head. The elongation of the telogen phase can be one-off as well as long-lasting and can be generated by various factors. The most important causes of telogen effluvium are:
- hormonal disorders accompanying menopause, pregnancy and postpartum period, hypothyroidism or hyperthyroidism
- heavy metal poisoning
- infectious diseases
- injuries and operations
- food shortages (mainly iron and zinc)
- long-term use of certain drugs (hormonal contraception, heparin, retinoids, non-steroidal anti-inflammatory drugs)
Sometimes it is difficult to determine the cause of telogen effluvium, because hair loss occurs after about three months of activation of the causative agent. Telogen effluvium in men and women is manifested in a similar way: hair thins over the entire surface of the scalp. This type of baldness is reversible – after the effect of the causative agent has subsided, hair should grow within 6 – 12 months.
Androgenetic alopecia is a common cause of hair loss in men, but also in women. When does androgenetic alopecia appear? The causes are an excess of male sex hormones, or androgens, that affect the hair follicles, leading to their miniaturization and hair loss. Androgenetic alopecia in men is associated with genetic predispositions, leading to increased sensitivity of the hair follicles to DHT, or dihydrotestosterone. That is why baldness occurs in the family, moreover, it appears quite early – even around 17-18 years of age. In turn, androgenetic alopecia in women results from hormonal disorders accompanying pregnancy, menopause, polycystic ovary syndrome. There is a disturbance of the proportion between female and male sex hormones.
How to recognize androgenetic alopecia? In men, the hairline starts to recede characteristically- hair starts falling out in the frontal and parietal parts. In turn, women notice hair thinning on the top of the head, with intact hair on the frontal line. Often, androgenetic alopecia in women is accompanied by hirsutism, i.e. excessive body hair, as well as acne and overweight.
Alopecia areata are excessive hair loss of non-inflammatory nature. Autoimmune processes are at the root of autoimmune hair loss when the body synthesizes antibodies that destroy the hair follicles. Alopecia areata may also be caused by chronic stress. Alopecia areata have a very characteristic course – hair loss occurs focal on oval areas with a diameter of 5 – 10 cm. Around the outbreaks of baldness, so-called exclamation hair appear, which are broken hair with a thicker diameter. This type of alopecia occurs in children and adults; most often the hair grows back spontaneously after a few months.