Hair loss, or alopecia, can be the manifestation of various diseases. Identifying the type allows us to provide specific solutions. We find entities as diverse as mucinous alopecia, discoid lupus erythematosus, lichen planopilaris, frontal fibrosing alopecia, alopecia areata, etc.
Some of these have a hormonal component, namely androgenetic alopecia, commonly called male-pattern or female-pattern baldness, with specific differences in distribution patterns and possible treatments depending on the gender. It is a problem that occurs after puberty (a phase of hormone increase), and its prevalence increases with age. This time, we’ll focus on male-pattern baldness.
Dr. Celia Gonzalo Gleyzes – Neolife Medical Team
Some basic concepts of trichology (the study of the hair and scalp)
Hair follows a cycle with different evolutionary phases. About 90% of the hairs on your head are in the anagen phase; this is the growth phase that can last from 2 to 6 years. Next comes the catagen phase (less than 1% of the follicles are in this phase), which lasts around 3 weeks. In this phase, growth stops, and there is a regression of the lower part of the follicle. And finally, we have the telogen phase, the phase during which hair falls (it is estimated that between 50 to 150 hairs are lost per day).
As for hair types, we will classify them into two categories: terminal hair (the follicle is located in subcutaneous fat tissue; hair diameter of 0.06 mm) and vellus hair (the follicle is located in the reticular dermis; hair diameter of 0.03 mm).
The term “intermediate hair” is sometimes used to describe those that have intermediate characteristics.
Androgenetic alopecia (AA) in men
It is a problem that occurs after puberty (a phase of hormone increase), and its prevalence increases with age. In some ethnic groups, like the Korean, it is less common.
Androgenetic alopecia is dependent on androgens (male hormones) but requires a genetic predisposition. This way, males who have androgen insensitivity syndrome do not develop this type of alopecia.
The key to the issue is dihydrotestosterone (DHT), a potent metabolite of testosterone that has greater affinity for the androgen receptor.
The enzyme responsible for transforming testosterone into DHT is 5-alpha-reductase, and it exists in two isoforms (type 1 and 2). Type 2 is more important.
Young males with AA have higher levels of 5-alpha-reductase and a higher density of androgen receptors in the part of the scalp that has lost more hair. In some individuals with AA, higher levels of free testosterone (testosterone not bound to proteins) are also evident.
Inheritance is an important factor; having a parent with alopecia increases your chances of having it at some point by five.
The perception of hair loss is the result of the shortening of the anagen phase of the hair follicles, which makes the hair very thin and short, like vellus hair. This process is called “miniaturization”. This transformation is accompanied by apoptosis (cell destruction).
Even if the hormonal component takes center stage, other factors such as prostaglandin-mediated signals are also involved.
Hair loss begins in the temporal zone, in the front or at the vertex (crown); this varies among individuals. AA evolves slowly over the years, but sometimes peaks of hair loss occur.
Some studies with varying results link AA to cardiovascular disease and metabolic syndrome.
A systematic review and meta-analysis found a link between alopecia located on the crown and a higher risk of prostate cancer.
Androgenetic alopecia must be differentiated from entities like receding hairline, alopecia areata, traction alopecia, scarring alopecia, and trichotillomania (hair-pulling disorder) (2,3).
Treatments for androgenetic alopecia in men
Known commercially as Proscar or Propecia, finasteride is a competitive inhibitor of 5-alpha reductase type 2. It has been shown that 1 mg of the drug decreased DHT by 60%. This drug has no affinity for the androgen receptor. Age is a factor to consider; treatment is more effective in young men (18-41 years) than in older men (41-60 years). To fully verify its effectiveness, the treatment must be followed for at least 12 months.
In terms of the most common side effects, there may be cases of erectile dysfunction, decreased libido, problems with ejaculation, and lower sperm quality.
Dutasteride is also used; this drug inhibits the two types of 5-alpha-reductase. Compared to finasteride, dutasteride is a 3 times more potent inhibitor of the 5-alpha-reductase type 2 and 100 times more potent inhibitor of type 1. This reduces DHT by 93-94%.
In the first line of treatment, we also have minoxidil, a molecule that promotes hair growth by increasing the anagen phase, shortening the telogen phase, and helping miniaturized follicles increase in size. Minoxidil is a vasodilator. Among the most effective concentrations, the 5% foam is often preferred. An initial hair loss may occur in the first two months of treatment. The most effective first-line therapy would combine finasteride/dutasteride plus minoxidil.
Another possible treatment would be platelet-rich plasma (PRP) obtained through blood drawn from the patient himself. PRP is an amalgam of growth factors in large concentrations. These factors are involved in numerous processes such as angiogenesis, cell proliferation and differentiation. The therapeutic effect of these injections onto the scalp is that they prolong the anagen phase of the hair follicle and prevent premature entry into the catagen phase (5).
Low level laser therapy (LLT) may also be applied on the scalp. The action mechanism would consist of an acceleration of cell division (mitosis), the stimulation of hair follicle stem cells or follicular keratinocytes, effects on cell metabolism, and anti-inflammatory actions (6).
We will also mention the usefulness of using topical prostaglandins (latanoprost) and shampoo with ketoconazole at 2%.
And if hair loss is already chronic and extended, we may resort to surgery, in other words, hair implants. The goal is to “repopulate” the areas that have suffered hair loss. Hair follicles are extracted from the occipital area, where hair is more resistant to androgenetic alopecia, and are transplanted to the desired area. It is very important to continue topical treatment to prevent further hair loss (7).
BIBLIOGRAPHY
(1) Up To Date: Evaluation and diagnosis of hair loss
(2) Up To Date: Androgenetic alopecia in men: Pathogenesis, clinical features, and diagnosis
(3) https://www.sciencedirect.com/science/article/pii/S0306987717310411?via%3Dihub. Med Hypotheses. English RS Jr1.
(4) Up To Date: Treatment of androgenetic alopecia in men
(5) https://www.ncbi.nlm.nih.gov/pubmed/30261560
(6) https://link.springer.com/article/10.1007%2Fs10103-017-2385-5
(7) Up To Date: Treatment of androgenetic alopecia in men