Does Finasteride Affect Male Hormones? A Comprehensive Guide

October 9, 2025 •

5 min read

Finasteride, a widely prescribed medication for male pattern hair loss and benign prostatic hyperplasia, is known to significantly reduce the male hormone dihydrotestosterone (DHT). Understanding how finasteride affects male hormones is essential for any man considering or currently undergoing treatment.

Quick Summary

Finasteride inhibits the conversion of testosterone into dihydrotestosterone (DHT), leading to reduced DHT levels and a potential temporary increase in circulating testosterone. This hormonal change underlies its therapeutic effects but can also contribute to side effects in some individuals.

Key Points

Mechanism of Action: Finasteride works by blocking the 5-alpha reductase enzyme, which prevents the conversion of testosterone to dihydrotestosterone (DHT).
Significant DHT Reduction: The medication causes a substantial drop in serum and scalp DHT levels, which helps to slow or reverse hair loss.
Minimal Impact on Testosterone: While testosterone levels may see a small, transient increase initially, long-term use typically results in stable total testosterone levels within the normal range.
Altered Hormonal Balance: By reducing DHT, finasteride can subtly alter the balance between androgens and estrogen, potentially leading to side effects like gynecomastia in some individuals.
Potential Neurosteroid Effects: Alterations in neurosteroid levels in the brain may contribute to reported mood changes, anxiety, and other non-sexual side effects.
Consult a Healthcare Provider: Due to individual variability in hormonal response and potential side effects, consultation with a doctor is vital before starting or continuing finasteride.

Understanding the Hormonal Mechanism of Finasteride

Finasteride belongs to a class of drugs known as 5-alpha reductase inhibitors (5-ARIs). The enzyme 5-alpha reductase is responsible for converting testosterone into the more potent androgen, dihydrotestosterone (DHT). Finasteride works by blocking the action of the type 2 isoform of this enzyme, which is primarily active in the hair follicles and prostate. By inhibiting this conversion, finasteride significantly lowers the amount of DHT in the body.

This deliberate manipulation of the body's endocrine system, while effective for treating hair loss and benign prostatic hyperplasia (BPH), directly impacts the natural balance of male hormones. The most pronounced effect is the reduction of DHT, but the hormonal chain reaction doesn't stop there. The overall impact on a man's hormonal profile is a complex interplay that can vary from person to person.

The Relationship Between Finasteride, Testosterone, and DHT

To understand the full hormonal effect, it's crucial to distinguish between testosterone and DHT. While testosterone is the primary male sex hormone, DHT is a more potent androgen that binds to androgen receptors more effectively. Many of testosterone's effects in tissues like the prostate and hair follicles are mediated by its conversion to DHT. When finasteride inhibits this conversion, it creates a cascade of hormonal adjustments.

Impact on Dihydrotestosterone (DHT): The most direct and desired effect of finasteride is the drastic reduction of DHT levels. Studies show that finasteride can reduce serum DHT significantly. This reduction is the key to preventing hair follicle miniaturization in men with androgenetic alopecia. In BPH, finasteride can lead to a significant reduction in prostate-specific DHT levels.
Impact on Testosterone: A common concern is that finasteride will lower testosterone levels. However, since the medication blocks the conversion of testosterone to DHT, a temporary and modest increase in circulating testosterone can occur. This is because the available testosterone that would have been converted remains in the bloodstream. Over time, the body's feedback mechanisms often lead to a re-stabilization of total testosterone levels within the normal range. Long-term studies show minimal lasting impact on overall testosterone concentration.
Impact on Estrogen: With less testosterone being converted to DHT, some of the remaining testosterone can be converted into estrogen via a process called aromatization. While this effect is more pronounced in older men and those taking higher doses, it can subtly shift the androgen-to-estrogen ratio. This hormonal shift is thought to be a contributing factor to potential side effects such as gynecomastia (breast tissue enlargement) in a small percentage of users.

Neurosteroid Effects and the Brain

Beyond the reproductive system, finasteride's inhibition of 5-alpha reductase also affects neurosteroids—steroid hormones produced in the brain. Some neurosteroids, which modulate important functions like mood and libido, are downstream metabolites of 5-alpha reductase. Research suggests that finasteride's alteration of these neurosteroid levels may contribute to some of the reported non-reproductive side effects, including depression and mood changes. The potential long-term, and sometimes persistent, symptoms known as Post-Finasteride Syndrome (PFS) are often attributed to these complex and not fully understood neurosteroid pathway disruptions.

Potential Hormonal Side Effects and Considerations

While finasteride is generally well-tolerated, the alteration of hormonal levels can lead to a range of side effects in a small number of men. The severity and persistence of these effects can differ based on the dosage and individual physiology.

Comparison of Hormonal Effects: Finasteride vs. Untreated


Hormonal Marker	Untreated Men	Men on Finasteride	Potential Side Effects
Serum DHT	Normal physiological range	Significantly reduced	Hair regrowth, prostate shrinkage. Potential sexual and mood side effects related to altered androgen activity.
Serum Testosterone	Normal physiological range	Initial slight increase, stabilizes to normal range over time	Generally none, as total levels remain stable. Sexual dysfunction is not typically linked to low testosterone on finasteride.
Serum Estrogen	Normal physiological range	Potential modest increase in some individuals, especially with higher doses	Gynecomastia (breast enlargement), breast tenderness.
Neurosteroids	Normal production and balance	Altered levels of some neurosteroids	Depression, anxiety, and cognitive complaints.

Other Hormonal Considerations

Fertility: Finasteride can decrease semen volume and sperm count in some men. Although the changes may persist for some after stopping the medication, it is unclear how this impacts long-term fertility. Concerns should be discussed with a healthcare provider, especially if planning to conceive.
PSA Testing: Finasteride lowers serum Prostate-Specific Antigen (PSA) levels, a biomarker used to screen for prostate cancer. It is critical to inform your doctor if you are taking finasteride before a PSA test so they can interpret the results accurately.

Conclusion

Does finasteride affect male hormones? The answer is a definitive yes. The medication's therapeutic benefits for hair loss and BPH are directly dependent on its ability to inhibit the 5-alpha reductase enzyme and significantly lower DHT levels. While this can cause a transient and minor increase in circulating testosterone, the body generally compensates, and long-term total testosterone levels remain stable within the normal range. The hormonal changes are not limited to testosterone and DHT, potentially influencing estrogen levels and important neurosteroid pathways in the brain.

For the majority of users, finasteride is effective and well-tolerated. However, it is essential to be aware of the potential side effects, including sexual dysfunction and mood changes, which are thought to be related to the hormonal shifts. Before starting or continuing treatment, men should have a comprehensive discussion with their healthcare provider about these hormonal effects, particularly if they have a history of sexual dysfunction, infertility, or depression. Open communication and awareness are crucial for making an informed decision about finasteride therapy. Further research, particularly into neurosteroid effects and the long-term impacts of PFS, is ongoing.

For more detailed clinical data on finasteride's hormonal effects, an in-depth review can be found on the National Institutes of Health website. https://www.ncbi.nlm.nih.gov/books/NBK513329/

Important Hormonal Players in Finasteride Use

Testosterone: The primary male androgen, responsible for muscle mass, libido, and bone density.
Dihydrotestosterone (DHT): A more potent androgen converted from testosterone; implicated in male pattern baldness and prostate enlargement.
5-Alpha Reductase: The enzyme that converts testosterone into DHT.
Neurosteroids: Steroid hormones produced in the brain that influence mood, libido, and other neurological functions.
Estrogen: Female sex hormone; in men, some testosterone is converted to estrogen.

Frequently Asked Questions

No, finasteride does not typically cause low testosterone. It works by blocking the conversion of testosterone to DHT, which can lead to a small, temporary increase in circulating testosterone. Long-term use generally sees testosterone levels return to a stable, normal range.

Sexual side effects like reduced libido and erectile dysfunction are thought to be primarily linked to the decrease in DHT, not low testosterone. DHT plays an important role in sexual function. Additionally, alterations in neurosteroid levels are believed to contribute to mood and libido changes in some users.

Both are male hormones, but DHT is a more potent androgen converted from testosterone by the 5-alpha reductase enzyme. While testosterone is the primary male sex hormone, DHT is responsible for certain functions, including its role in male pattern baldness and prostate growth.

Yes, it can. By reducing the conversion of testosterone to DHT, finasteride can lead to a slight increase in circulating testosterone. Some of this increased testosterone may then be converted into estrogen via the aromatization process, an effect that is more common in older males.

For most men, hormone levels, including DHT and testosterone, return to their pretreatment levels within a few months after stopping finasteride. However, some men report persistent side effects even after discontinuation, a condition sometimes referred to as Post-Finasteride Syndrome.

Some men report mood changes, including depression and anxiety, while taking finasteride. Research suggests that these effects may be linked to the drug's impact on neurosteroid pathways in the brain, although the incidence is low.

Yes. Higher prescribed amounts of finasteride, such as those used for BPH, are associated with a greater reduction in DHT and may be more likely to cause certain side effects compared to lower amounts typically used for hair loss.