Many causes of hair loss and hair thinning are due to the interruption of the hair growth cycle, which has three phases – anagen (growth phase), catagen (follicle renewal) and telogen (resting). Hair normally sheds at the end of the telogen phase as a new hair pushes through, but a disrupted cycle could mean that hair sheds before new growth is fully ready2.
Heredity, underlying medical conditions, or environmental causes like stress and unhealthy lifestyle choices could all be reasons for hair thinning, and in some cases progressing to a partial loss of hair (e.g. a receding hairline) or even total loss of hair on the head.
Genetics is one of the main reasons for hair loss in men. If you have a family history of hair loss, it is possible that you will experience it too, and that fact holds true for both males and females. However, there are other reasons our hair thins or falls out, some of which we can control. Other causes include:
Hormonal changes, especially increases in dihydrotestosterone (DHT), the male sex hormone. DHT affects the hair follicles, making them produce smaller and shorter in length, until shrinking completely and not producing any more hairs3. Some hormonal changes may be age-related.
Extreme dieting and malnutrition – hair grows from inside the body, so if the body is not supplying the correct nutrients hair growth may be substandard.
Medical and genetic conditions such as alopecia areata (the medical term for losing more hair than is replenished, resulting in thinning or balding.
Occurring at any age, alopecia primarily affects the scalp and can sometimes disrupt hair growth on beards, eyebrows, eyelashes and other parts of the body) and male pattern baldness.
Medications and treatment used for diseases like arthritis and heart problems, and radiation for cancer patients
Environmental factors such as polluted air or water
Damage to the hair follicles through excessive straining (as with certain hairstyles) or harsh chemical treatments