A healthy person not experiencing any hair loss loses 50 to 100 hairs every day. Lost hairs in a healthy person will be replaced shortly by new hairs. In other words, there is a balance between hair loss and hair growth, and a person's hair mass is maintained at an almost constant level over time. What you will read:
Hair growth stages
In humans, there are three stages or phases between hair growth and hair loss which are:
- Anagen phase or growth stage
- Catagen phase or intermediate stage
- Telogen phase or resting stage
Let's look into each of these stages in more details:
Anagen phase or growth stage:
In this stage, the cells in the hair follicle are multiplying rapidly and the new hair pushes the old hair upwards. As a result, every four weeks one centimeter is added to the length of our hair. anagen phase lasts for two to six years in the scalp and during which hair grows. The anagen phase in the hairs of other parts of our body lasts only thirty to forty-five days, and this is why these hairs grow less.
Catagen phase or intermediate stage:
This phase lasts two to three weeks. In this phase, the hair no longer grows and it prepares to fall.
Telogen phase or resting stage:
The hair stays in this stage for about three months until the new hair pushes the old hair out, and thus the hair separates from the head and falls off. Fifty to one hundred of our hairs that are in the telogen phase are shed daily.
In the cases listed blow as telogen effluvium, a person looses much larger number of hair. Telogen effluvium may occur three months after any of the following events:
- A severe fever
- Giving birth
- Surgery
- Severe systemic disease
- Loss of a loved one
- Emotional psychological shock
It usually takes six months to a year for lost hair to grow back. Hair loss is a disease and happens when the balance between hair loss and growth is changed and the lost hair is not replaced with a new one and the hair volume decreases over time.
Pathological hair loss (known as "alopecia" in medical terms), has many different types and causes:
Patchy hair loss:
We would say someone has a patchy or circular hair loss when he or she looses a patch of hairs at once in one small area of the head. This type of hair loss is mostly seen in the following cases:
- Anxiety
- Diabetes
- Hyper thyroid
- Down syndrome
- Genetics and family history
Alopecia with scar (alopecia cicatricial):
Lichen planus and any disorder or disease that causes permanent destruction of hair follicles by causing inflammation in the scalp.
Anagen effluvium:
A type of hair loss happening after any of the following events:
- Chemotherapy
- Radiotherapy
- Immune therapy
In most cases, we will see that the hair grows after these treatment.
Telogen effluvium:
Hair loss can also be because of the following reasons and cases:
- Hormonal changes
- Giving birth
- Severe systemic infections
- Severe fever
- Recent surgery
- Severe psychological and emotional stress
- Diet change
- Loss of a loved one
Drugs that cause hair loss:
Taking some pills and consumption of some drugs may result in hair loss. Some of these drugs are:
- Beta-blockers (antihypertension)
- Levothyroxine
- Vitamin A derivatives (oral and medicinal retinoids called acitretin used to treat psoriasis)
- Sertraline
- Sodium valproate (a drug used to treat epilepsy and prevent migraine attacks)
- Some blood cholesterol-lowering drugs (statins, especially pravastatin)
- Hormonal drugs
Cause of acquired hair loss
Acquired hair loss can be due to:
- Iron deficiency anemia
- Liver disease
- Selenium, zinc and magnesium deficiency
- Endocrine diseases
- Thyroid diseases, especially hyperthyroidism
It should also be noted that hormonal and genetic factors play an important roles in hair loss (known as hereditary and androgenetic hair loss) and it affects both males and females.
Anyone who sees a doctor for hair loss, the reason of hair loss will be diagnosed by first looking into hormonal and hereditary causes if none of the acquired causes are applicable.