Causes of male hair loss include genetic factors. A family history of hair loss increases the risk of developing the disease in male offspring and is associated with genetic variations in genes such as the androgen receptor gene.
There are also factors related to androgen levels, such as the conversion of androgen to dihydrotestosterone, which binds to hair follicle receptors and causes hair follicle miniaturization. There are also local factors on the scalp, such as excessive oil secretion, which breeds microorganisms that irritate the scalp, and inflammation around the hair follicles that damages the follicles. There are also lifestyle factors, such as lack of sleep leading to hormonal imbalances, stress leading to the secretion of stress hormones, and an unbalanced diet with nutritional deficiencies that affect hair growth. There are also medical factors, such as endocrine diseases that slow metabolism, nutritional deficiencies caused by malnutrition, and infections that damage the hair follicle structure.
There is also a more persistent type of hair loss that is inherited and linked to genes. Many people are unaware that they are born with this destinie: hereditary hair loss.
What is hereditary hair loss?
Hereditary hair loss is caused by the androgen receptor (AR). Androgens influence gene expression in hair follicle cells. The AR gene is located on the X chromosome. Its protein activity is expressed by the number of glutamine (Gln) repeats in the protein sequence. Fewer Gln repeats indicate higher receptor activity, leading to a higher risk of androgenic alopecia (AGA). In men, if the number of Gln repeats in the AR protein is less than 21, the risk of developing androgenic alopecia (caused by excess androgens) is nearly 97%. In women, the risk is higher than 96%. However, if the number of Gln repeats is 26 or more, the risk of not experiencing hair loss is 80%.
Androgenic alopecia is a common condition in men, ultimately manifesting as a decrease in the number of anagen hairs, specifically a shortened anagen phase and a decreased proportion of hairs, and a prolonged telogen phase and an increased proportion of hairs. While its etiology is not fully understood, current research suggests that AGA is an androgen-dependent, polygenic genetic disorder linked to androgens and genetic mutations, particularly those in the androgen receptor gene. Simply put, hereditary hair loss occurs more often in men and tends to run in families. If a father experiences hair loss, the chances of male offspring experiencing hair loss are very high. However, it's worth noting that women also have a certain chance of developing hereditary hair loss.
What is the probability of hereditary hair loss? Are there any differences between men and women?
Data research reveals the following conclusions regarding hereditary hair loss:
- Among those with a family history of hair loss, approximately 60% of men experience it, while approximately 30% of women do.
- A family history of hair loss causes hair follicles to gradually shrink and close. Women typically experience overall hair loss, while men typically experience hair loss starting at the hairline and eventually spreading to the crown.
- Paternal hair loss is more likely to be passed down to the next generation. Among men with a family history of hair loss, 44.9% have a paternal-only family history, while 17.2% have a female-only family history.
- The probability of hereditary hair loss being passed down from father to child is 50%, and from grandfather to grandchild is 25%. Studies have also found that those with a family history of hair loss develop the condition at an earlier age and experience higher levels of hair loss. In summary, while parental hair loss can have a significant impact on the hair of their offspring, it's not 100% hereditary, so there's no need to worry too much.