Alopecia androgenetica

Androgenetic alopecia is the most common form of hair loss in men and women.
The prevalence rate in men in their 30s, 40s, and 50s in the Caucasian population is approximately 30%, 40%, and 50%, respectively.
The overall prevalence among adult women is 32.3%, with prevalence increasing with age: from 8% in the 20–29 age group to 68% in women aged 60–75 (Müller Ramos et al., 2023).
Caucasians are most affected, while people of Asian, Native American, or African American descent are less affected.

The classification is based on gender.

Norwood–Hamilton scale (1951/1975) (men) (Bouhanna et al., 2000)

Stage I: Normal hair growth
Stage II: Receding hairline
Stage III: Tonsure-like, occipital-parietal hair thinning, hair bridge still present
Stage IV: Almost complete hair loss in the parietal area, with a lateral and posterior hair rim remaining
Stage V: Thin, ring-shaped, occipital and parietal residual hair

Ludwig scale (1977) (women) (Bouhanna et al., 2000):

Stage I: Incipient hair thinning in the parting region, only noticeable when parting the hair
Stage II: Clearly visible hair thinning in the parting area, the frontal hairline is becoming visible
Stage III: Pronounced baldness in the frontoparietal region, existing frontal hairline

Basic and specific classification (2007) (universal for women and men) (Lee et al., 2007)

There are four basic types (L, M, C, U) and two specific types (V, F). Each type is divided into three or four sub-types depending on severity. The basic types describe the shape of the front hairline. The specific types refer to the hair density of the frontal and vertex regions. The final hair loss type is determined by combining a basic type with a specific type (if applicable) (Lee et al., 2007).

The interaction of genetic, hormonal, and metabolic factors as well as microinflammation is crucial for the development of androgenetic alopecia.
Susceptibility to androgenetic alopecia is mainly influenced by hereditary factors.
Androgenetic alopecia follows a polygenic model, largely consisting of gene polymorphisms of the androgen receptor (AR) genes on the Xq12 chromosome, accompanied by increased receptor activity in the hair follicles after binding of dihydrotestosterone.
The mutated androgen receptors in the hair follicles bind to dihydrotestosterone and initiate an enhanced signaling cascade that leads to a shortening of the anagen phase and, as a result, to thinner and shorter hair, in the sense of a miniaturization of the hair follicles. The terminal hairs are replaced by vellus hairs.
Occipital hair is less sensitive due to its androgen receptor methylation.
In women, it rarely occurs secondarily to other underlying diseases (e.g., polycystic ovary syndrome) that lead to elevated peripheral androgen levels.

The diagnosis is made clinically. Pull tests, dermatoscopy, and trichograms are useful. A scalp biopsy may also be performed if necessary.
Macroscopically, hair thinning is found in the androgen-sensitive areas of the scalp.
The hair pull test should be performed both frontally and occipitally. In androgenetic alopecia, the pull test is only positive frontally and not occipitally, in contrast to telogen effluvium.
Reflected light microscopy reveals anisotrichosis >20% in the androgen-sensitive areas.
Diagnostic features of androgenetic alopecia in the trichogram include increased hair shaft diameter diversity, shortening of the hair, dystrophic hair, and an increased telogen hair rate.
Any substrate deficiency (e.g., ferritin, zinc, vitamin D, vitamin B12, folic acid) that may promote effluvium should always be ruled out.
Hormone tests are generally not indicated in men.
In women, if there are corresponding anamnestic indications of hyperandrogenemia (including hirsutism, pronounced acne, seborrhea, irregular menstrual cycles, infertility, clitoral hypertrophy, metabolic syndrome, known PCOS) or hyperprolactinemia (including galactorrhea), an endocrinological evaluation (referral to a specialist (endocrinology/gynecology)) is recommended.

General

Exogenous toxins such as nicotine consumption should be avoided (Su et al., 2007).
Concomitant scalp conditions such as seborrheic dermatitis should be treated (e.g., with Sebiprox, Sebolox, or Nizoral shampoo).
Substrate deficiencies should be corrected.
Drug therapy depends on gender.
To date, only two drugs, oral finasteride (for men) and topical minoxidil (for men and women), have been approved by the FDA for the treatment of AGA.
The patient should be informed that the therapeutic effect of a medication can only be maintained with regular and consistent use.

Topical therapy:

Minoxidil solution/foam/shampoo (e.g., Regaine, Alopexy, Lonolox, magistral formulation):
- For men: Minoxidil 5% twice daily.
- For women: Minoxidil 2% twice daily or 5% once daily.
- Presumed mechanism of action: By dilating the blood vessels in the scalp, the supply of nutrients to the hair follicles may be improved.
- To optimize effectiveness, it is recommended to massage minoxidil into the scalp.
- In approximately 50% of cases, visible thickening of the hair is observed after 3-6 months.
- Side effects: Unwanted facial hair, local scalp irritation, and initial worsening of hair loss in the first 6-8 weeks.

Finasteride spray (e.g., FYNZUR Spray):
- Off-label use
- Topical finasteride 0.25% once daily appears to be about as effective as oral finasteride in improving hair density with fewer systemic side effects (Hajheydari et al., 2009).
- Must not come into contact with pregnant women under any circumstances (risk of genital malformations in male fetuses).
- Combination with topical minoxidil for potentially better results.

Systemic therapy:

Finasteride 1 mg/day p.o. (in label, e.g., Propecia) or duasteride 0.5 mg/day p.o. (off-label)
- Finasteride p.o. at a dosage of 1 mg/day is approved for adult men with mild to moderate androgenetic alopecia (especially useful for men < 35 years of age).
- Finasteride inhibits type II 5α-reductase, thereby reducing serum, prostate, and scalp dihydrotestosterone levels by 60% to 70%.
- Combination therapy with oral finasteride 1 mg and topical minoxidil 2-5% is superior to monotherapy with finasteride.
- Before starting therapy with finasteride, patients should be informed about potential side effects such as libido/potency problems, depression/anxiety and gynecomastia. Such side effects may persist for months or even years after discontinuation of finasteride in the form of post-finasteride syndrome.
- The diagnosis of prostate cancer may be more difficult due to falsely low PSA levels under finasteride.
- Finasteride tablets should not be touched by pregnant women due to the potential risk to male fetuses (genital development). The same applies to topical finasteride, which must also not come into contact with pregnant women under any circumstances.
- A large Japanese study showed that within a period of three years, 11.1% of participants taking finasteride experienced significant hair regrowth, while 36.5% experienced moderate growth and 39.5% experienced slight improvement in hair growth. (Sato et al., 2012).

Minoxidil p.o. (e.g., Lonolox)
- Off-label use in women and men.
- If there is no response after 3-6 months of topical minoxidil use, off-label use of oral minoxidil may be discussed.
- Observe contraindications!
  - Contraindicated in pregnancy/breastfeeding, pulmonary hypertension due to mitral stenosis, and known pheochromocytoma, among other conditions.
  - If in doubt, consult a specialist (cardiologist) before starting treatment.
- It should be administered slowly (for women, initially 0.625 mg once daily for 3 months, then max. 1.25 mg once daily, or for men, initially 1.25 mg-2.5 mg once daily for 3 months, then increase depending on tolerance to max. 5 mg once daily).
- Side effects (excerpt): Initial shedding, hypertrichosis, edema including pericardial and pleural effusions, tachycardia, orthostatic hypotension, and dizziness.

Oral hormones
- Only in cases of peripheral hyperandrogenemia.
- Consultation with a specialist (endocrinology/gynecology) recommended.

Platelet-rich plasma (PRP)

Platelet-rich plasma (PRP), which contains numerous growth factors, may be considered as an adjuvant in the treatment of androgenetic alopecia.
There is some evidence of an additional benefit of PRP in combination with topical minoxidil in androgenetic alopecia (although evidence is limited) (Yao J et al., 2024).
PRP does not achieve a cure and would need to be continued long-term to maintain results.
There are different regimens: According to Gupta et al. (2019), it is recommended to perform PRP sessions once a month for 3 months, followed by a maintenance period every 3 to 6 months.
However, due to the relatively recent introduction of PRP injections for the treatment of androgenetic alopecia, there are no long-term studies evaluating its effectiveness.

Hair transplantation:

The indications for a hair transplant are (Zito et al., 2024):
- Androgenetic alopecia (Norwood stage III to V in men and Ludwig stage II in women)
- Traction alopecia
- Frontal fibrosing alopecia (inactive phase)
- Lichen planopilaris (inactive phase)
- Folliculitis decalvans (inactive phase)
- Restoration of facial hair (eyebrows, beard) after injuries or burns
To treat androgenetic alopecia, hair follicles are transplanted from non-androgen-sensitive areas to affected areas. This is based on the androgen resistance of the occipital hair follicles, which is also retained in the new location (donor dominance).
Contraindications:
- Young patients (a hair transplant should preferably be performed after the age of 25. Younger patients should initially receive drug therapy).
- Diffuse alopecia (lack of donor area)
- Unstable hair loss (rapid deterioration with >15% miniaturization in the area to be transplanted)
- Insufficient hair loss (patients with less than 50% hair loss of the original hair volume should be treated with medication first)
- Patients with unrealistic expectations
- Body dysmorphia
- Trichotillomania
In the case of a hair transplant, accompanying peri-interventional drug therapy (e.g., topical minoxidil and/or finasteride p.o. for men) is recommended.
- A study by Leavitt et al. (2005) in men showed that combining a hair transplant with oral finasteride 1 mg once daily (and/or topical minoxidil) starting 4 weeks before the transplant and continuing for 48 weeks after the transplant achieved better clinical results with increased hair density and reduced postoperative progression.
- Minoxidil solution 5% should be discontinued 2-3 days before surgery and resumed 5 to 7 days after surgery (Asfour et al., 2000; Zito et al., 2024).
Factors that negatively influence hair transplantation (Zito et al., 2024)
- Nicotine
- Diabetes
- Advanced hair loss
- Arterial hypertension
- Severe actinic damage to the scalp
Robot-assisted transplants also available (e.g., Artas).

Cosmetic options:

Wig, hairpiece, cover spray, or highlights.

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Alopecia androgenetica

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