What is the cause of alopecia (hair loss)?

From the Guidelines

Alopecia, or hair loss, is primarily caused by a chronic inflammatory disease affecting the hair follicles, with autoimmune factors and genetic predisposition playing a significant role, as indicated by studies such as 1 and 1. The exact cause of alopecia can vary depending on the type, but for alopecia areata, which is a common form of hair loss, the condition is characterized by an immune system attack on the hair follicles, leading to inflammation and subsequent hair loss. Some key points to consider about alopecia areata include:

• It can occur at any age and affects both males and females equally, with no specific racial predilection 1.
• The disease often presents as patches of hair loss on the scalp, but it can also affect any other hair-bearing area of the body.
• The presence of short, broken hairs, known as exclamation mark hairs, around the edges of the hair loss patches is a common feature of alopecia areata.
• Nail involvement is seen in about 10% of patients, further complicating the condition.
• The prognosis varies, with some patients experiencing spontaneous remission within a year, while others may progress to more severe forms like alopecia totalis or universalis, from which recovery is less common.
• Family history plays a role, with about 20% of patients having a family history of the condition, suggesting a genetic component.
• Associations with other autoimmune diseases and certain genetic markers, such as those related to the major histocompatibility complex, cytokine, and immunoglobulin genes, support the idea of an autoimmune etiology 1. Given the complexity and variability of alopecia, it is crucial for patients to consult a dermatologist for an accurate diagnosis and to discuss the most appropriate treatment options, which may include topical or intralesional corticosteroids for alopecia areata, or other treatments like minoxidil or finasteride for different types of hair loss, as these treatments can help manage the condition and improve quality of life, as noted in guidelines such as those from 1.

From the Research

Causes of Alopecia

The exact cause of alopecia, or hair loss, is complex and multifaceted. However, research suggests that androgenetic alopecia, the most common form of hair loss, is influenced by:

• Genetic factors 2, 3, 4, 5
• Systemic androgens, which lead to follicular miniaturization 4, 6
• Dihydrotestosterone (DHT), a potent form of testosterone that contributes to hair loss 2, 6

Role of Dihydrotestosterone (DHT)

DHT is a key player in the development of androgenetic alopecia. It is converted from testosterone by the enzyme 5α-reductase, and its levels can be suppressed by medications such as finasteride and dutasteride 6. These medications work by inhibiting the 5α-reductase enzyme, thereby reducing DHT levels and promoting hair growth.

Other Factors

While the exact causes of alopecia are not fully understood, research suggests that other factors may contribute to hair loss, including:

• Hormonal imbalances 4, 6
• Age and puberty 5
• Stress and psychological factors 5
• Certain medical conditions and medications 5

Treatment Options

Various treatment options are available for alopecia, including:

• Topical minoxidil solution 2, 3, 4, 5
• Oral finasteride and dutasteride 2, 4, 6
• Low-level laser therapy (LLLT) 2, 3
• Hair transplantation 5
• Other novel treatments, such as autologous platelet-rich plasma and adipose-derived stem cells 4