Hair loss is a common and frustrating issue that affects millions of men—often starting as early as their 20s or 30s. If you’ve noticed a receding hairline or thinning at the crown, you’re not alone—and you’re not without options. Finasteride, a once-daily oral medication, is one of the most clinically proven treatments available for male pattern hair loss (androgenetic alopecia).
In this guide, we’ll break down how Finasteride works, what kind of results you can expect, how long it takes to see improvement, and what side effects to watch for. Whether you’re just beginning to notice hair loss or exploring ways to maintain your current hair, this overview can help you decide if Finasteride is the right fit for your treatment plan.
The Androgenic Hormones
There are two relevant androgenic hormones in the male when discussing male pattern baldness: testosterone and its derivative dihydrotestosterone. These hormones have the following effects:
Testosterone
- In utero: Wolffian duct derivatives (seminal vesicles, vas deferens, epididymis, ejaculatory ducts)
- After puberty: Muscle mass, deepening voice, libido, growth of external genitalia, sperm production (Marks, 2004)
Dihydrotestosterone (DHT)
- In utero: Development of the male external genitalia
- After puberty: Facial acne and beard, male pattern baldness, prostate growth (Marks, 2004)
5α-reductase is an enzyme (a protein in the body that speeds up a chemical reaction) with two forms, type I and type II.
- Type I 5α-reductase is more prevalent in the liver, nongenital skin, scalp, sebaceous gland, brain, ovary, prostate, and testes.
- Type II 5α-reductase is more prevalent in the prostate gland, epididymis, seminal vesicle, uterus, genital skin, breast, hair follicle, and testis.
5α-reductase catalyzes the conversion of testosterone to DHT. About ten percent of testosterone in all adults is converted to DHT. Scientists believed that drugs could be developed to shrink the prostate and relieve male-pattern baldness and androgen triggered acne by targeting 5α-reductase after the external genitalia were fully formed and mature (Marks, 2004). Finasteride is one of those drugs.
How Does Finasteride For Hair Loss Work?
Finasteride is a competitive inhibitor of Type II 5α-reductase. This means it inhibits the enzyme Type II 5α-reductase and decreases its ability to convert testosterone to DHT. By blocking Type II 5α-reductase, the conversion of testosterone to DHT is reduced by up to two-thirds (Gormley et al., 1990). Clinical trials testing Finasteride for hair loss were started in the 1980s and completed in 1992. The drug had demonstrated both safety and efficacy (Marks, 2004).
Finasteride reduces the amount of circulating DHT in the body by approximately 2/3rds and slightly increases testosterone levels. Finasteride does not affect other hormone levels, such as luteinizing hormone and follicle-stimulating hormone. This finding shows that finasteride for hair loss does not change the regulation of testosterone production (McClellan & Markham, 1999).
In those who are genetically predetermined, DHT shortens the growth phase of the hair from years to weeks or months and decreases the size of the hair follicle. The shortened growth phase results in hair that goes into a resting phase more quickly and falls out—the smaller hair follicle results in thinner, less coarse hairs.
Male pattern baldness affects about 80% of men before 80 (Hamilton, 1951). Using twin studies, scientists determined that approximately 80% of the variance or difference between men in terms of inherited male pattern baldness is attributed to genetics and 20% to environmental factors (Nyholt, 2003). More sensitive testing has shown that genetics accounts for closer to 50%. A genome-wide association study looking at variations in genetic code between men with and without male-pattern baldness showed that many genes contribute, both from the autosomes (nonsex chromosomes) and the Y chromosome (male sex chromosome) (Hagenaars et al., 2017).
Does Finasteride Really Work?
In two 1-year trials of 1553 men aged 18 to 41 years old with male-pattern baldness receiving 1 mg of finasteride daily, clinically significant increases in hair count were noted in the treatment group while participants in the placebo group had continued hair loss (Kaufman et al., 1998). These results were replicated in several other clinical trials. In a review of the literature, Whiting (2001) found that finasteride for hair loss produced hair growth in up to 66% of men with mild to moderate hair loss and stopped hair loss in 91% of men.
Potential Side Effects Of Finasteride Use
Each person metabolizes medications differently and therefore has a different risk/benefit profile. Scheduling a consultation with a licensed physician at Invigor Medical provides an opportunity to discuss how your diet, supplement intake, medications, medical conditions, and medical history can increase or decrease your risk of side effects from finasteride for hair loss.
Warnings And Precautions
The following are warnings and precautions for the use of finasteride as per the manufacturer of the brand name PROPECIA® and filed with the FDA.
- Finasteride is not indicated for use in women or children.
- Finasteride is not to be used or handled by women who are pregnant or may become pregnant. The hormonal disruptions can cause birth defects and pregnancy complications, especially in male fetuses.
- Finasteride causes decreased serum PSA. Delay in treatment can increase the risk of high-grade prostate cancer. Regular prostate exams are encouraged as well as investigating any increase in PSA levels.
- The primary route of metabolism for finasteride in the liver. Therefore, caution and/or dosage adjustment may be required in individuals with hepatic (liver) impairment or its use may be contraindicated entirely.
Finasteride for hair loss is generally well tolerated by most users. Side effects reported in more than one percent of users.
| Side Effect | Treatment Group (945 men) | Placebo Group (934 men) |
|---|---|---|
| Decreased libido | 1.8% | 1.3% |
| Erectile dysfunction | 1.3% | 0.7% |
| Ejaculation disorder | 1.2% | 0.7% |
| Discontinuation due to sexual adverse experiences | 1.2% | 0.9% |
Post marketing there have been additional side effects reported. These side effects have not been evaluated with a clinical trial. Since the population size of finasteride for hair loss users is unknown a reliable percentage and statistics cannot be determined.
- Allergic reactions: rash, itching, hives, and swelling of the lips and face
- Sexual dysfunction that persisted after treatment was discontinued. In a study evaluating persistent erectile dysfunction after discontinuing finasteride, 1.4% of 11,909 men experienced prolonged erectile dysfunction. This side effect was increased with longer drug exposure (Kiguradze et al., 2017).
- Male breast cancer and breast tenderness. Studies have shown conflicting results on a possible increased risk for breast cancer. Users should be aware of possible indicators of breast cancer including breast enlargement, swelling, pain, lumps, or nipple discharge.
- Depression
- Low blood pressure when standing
- Dizziness
- Headache
- Weakness
Finasteride has not shown any significant interactions with any other drugs in clinical trials.
Dosing
The recommended dosing for finasteride for the treatment of male pattern baldness is 1 mg taken once daily with or without food. Daily treatment of three months or more is necessary to see the effects of the medication. Finasteride must be continued long-term in order to maintain its effects. The results will usually reverse over a 12-month period after discontinuing treatment (McClellan & Markham, 2012).
Studies have demonstrated that taking finasteride and heavy use of alcohol, drinking at least 50 g of alcohol per day had between 1.39 and 2.56 increased risk (average about double the risk) of developing low-grade prostate cancer. This finding was felt to be due to decreased risk of prostate cancer in men taking finasteride with low or no intake of alcohol (Gong et al., 2009).
Purchasing Finasteride
Finasteride is only available by prescription from a licensed doctor. In order to obtain finasteride for hair loss, you need to discuss your medical history, current medications, supplements, herbal remedies, and health conditions with your prescriber, in order to determine if finasteride is safe and recommended for you. If approved, you can start to see real results from finasteride in around 3 to 6 months, with a majority of men seeing hair regrowth after two years of consistent use.
