### Androgenetic Alopecia and Finasteride
Androgenetic alopecia (AGA), commonly known as “seborrheic alopecia” or “male pattern baldness,” is the most common type of progressive hair loss. Its core cause is the excessive sensitivity of genetically predisposed hair follicles to androgens – particularly dihydrotestosterone (DHT). DHT shortens the anagen (growth) phase of the hair follicle, causing it to progressively miniaturize. This eventually leads to the production of thin, short vellus hairs until hair loss is complete.
### Mechanism of Action of Finasteride
Finasteride is an oral type II 5α-reductase inhibitor. This enzyme, primarily found in hair follicles, the prostate, and the skin, is responsible for converting testosterone into the more potent androgen, DHT. By competitively inhibiting this enzyme, finasteride significantly reduces DHT levels in both the serum and the scalp (typically by approximately 60%–70%). Concurrently, testosterone levels may increase slightly as a compensatory response, but the total androgen pool remains largely unchanged. Since DHT is the primary aggressor against hair follicles, lowering DHT concentration effectively “lifts the alarm” for the follicles, thereby slowing or even reversing the process of follicular miniaturization.
### Clinical Efficacy: Slowing Hair Loss and Promoting Regrowth
Multiple randomized, double-blind, placebo-controlled trials have confirmed the efficacy of finasteride for male AGA. After one year of continuous use, the progression of hair loss is stabilized (i.e., no further shedding) in over 80% of patients. Approximately 60%–70% of patients experience some degree of hair regrowth, with the vertex (crown) area typically showing the best response. The effect on frontal hairline recession is usually less pronounced, although some patients may also see improvement in their frontal hairline. Onset of action is generally noticeable 3–6 months after starting the medication, with optimal results seen after 12 months. Continued use is required to maintain these benefits; once treatment is discontinued, DHT levels rebound, and the balding process typically returns to its pre-treatment state within one year.
### Scalp Appearance Changes and Subjective Experience
Clinical studies indicate that after one year of finasteride use, patients show an average increase in hair count of approximately 10%–20%, while the placebo group continues to experience a decrease. Although this percentage may seem modest, given the progressive nature of hair loss, the ability to “stabilize” and even achieve a small increase in hair growth represents a significant improvement in both appearance and psychological well-being for patients. It is important to note that this effect does not restore hair to the density of adolescence but rather slows further loss and promotes partial regrowth. Outcomes vary depending on individual genetic background, the timing of treatment initiation, and medication adherence.
### Side Effects and Safety
Finasteride is generally well-tolerated; however, it does carry potential side effects related to sexual function. Large-scale studies show that approximately 2%–4% of men may experience decreased libido, erectile dysfunction, or reduced ejaculate volume. These effects typically occur early in the treatment course and are usually reversible upon discontinuation. A small number of users report more persistent side effects (a condition sometimes referred to as “post-finasteride syndrome”), although this phenomenon lacks a unified diagnostic criterion and requires further research. Additionally, serum PSA (prostate-specific antigen) levels are typically reduced by about 50%; therefore, patients must inform their doctor about finasteride use when undergoing prostate disease screening. Rarely, gynecomastia (male breast development) or depressed mood may occur. Caution is advised in patients with hepatic impairment, and finasteride is contraindicated in women who are or may become pregnant, due to the risk of adverse effects on the external genitalia of a male fetus.
### Target Population and Precautions
Finasteride is approved only for the treatment of male AGA (in individuals aged 18 and older). Its efficacy is limited in postmenopausal women with hair loss, and its use is not recommended in this population; it is absolutely contraindicated in women who are pregnant or planning to become pregnant. The optimal time to initiate treatment is in the early stages of hair loss (Hamilton-Norwood stages II–IV), when hair follicles have not yet undergone complete fibrosis, allowing the medication to exert its maximum effect. Combining finasteride with topical minoxidil can produce synergistic benefits, but both treatments require long-term adherence. A consultation with a physician is necessary before use to rule out other causes of hair loss, such as thyroid dysfunction or iron deficiency anemia. This medication is a prescription drug and should not be purchased without a prescription.
**For reference only, does not constitute medical advice.**