They stopped taking finasteride, but the side effects didn’t stop.
- Sex, sleep, mood, masculinity — destroyed, by a pill for hair loss.
- Thousands affected worldwide — men and women.
- Recognised on paper. Not in practice — no code, no treatment.
Finasteride blocks an enzyme that makes at least five different hormones — not just DHT.Traish, Endocrine Practice 2012
The FDA estimates only 1–10% of drug reactions are ever reported — so every count on this page is a floor, not the real number.FDA FAERS
Roughly 7 million US prescriptions a year. Even a 1% rate is tens of thousands of people.FDA prescription data
Fifteen years after the label changed, there's still no dedicated ICD code to diagnose it by — so it can't be formally counted.ICD
What is Post-Finasteride Syndrome?
Post-Finasteride Syndrome (PFS) is a constellation of persistent sexual, neurological, and physical symptoms that continue — sometimes indefinitely — after stopping finasteride, a drug prescribed for hair loss (Propecia, 1mg) and enlarged prostate (Proscar, 5mg).
Finasteride blocks 5-alpha reductase, an enzyme that converts testosterone to DHT (dihydrotestosterone). While this reduces hair loss, it also disrupts neurosteroid production in the brain — hormones critical for mood, cognition, sexual function, and sleep.
Research by Prof. Roberto Melcangi at the University of Milan has shown that these disruptions can cause epigenetic changes — alterations to how genes are expressed — that research suggests may persist long after the drug has cleared the body.
Symptoms of PFS
PFS affects sexual, neurological, and physical health. Symptoms can appear during treatment or after stopping.
Sexual
5- Complete loss of libido
- Erectile dysfunction
- Weak or pleasureless orgasms
- Genital numbness
- Reduced ejaculate volume
Neurological
5- Severe brain fog
- Memory impairment
- Insomnia
- Emotional numbness
- Depersonalisation
Physical
5- Chronic fatigue
- Muscle wasting
- Joint pain
- Skin thinning
- Gynecomastia
This list is not exhaustive — it reflects the symptoms most commonly reported by patients, not every symptom that has been described.
PFS by the numbers
The reported numbers above are likely an undercount. The FDA estimates that only 1–10% of adverse drug reactions are ever reported, and academic studies put the figure lower still. On that basis the 11,557 FAERS reports are likely to represent a fraction of the people affected.
Reporting is also spread across countries and coding systems. One patient's symptoms may be recorded under several separate organ-class codes — sexual dysfunction in one, mood in another, cognition in a third — which makes a single underlying pattern hard for any one database to show. Establishing the true prevalence remains an open research question.
Regulatory timeline
How the regulatory picture has developed since finasteride was first approved.
Proscar approved (5mg)
FDA approves finasteride for enlarged prostate. Side effects described as reversible.
Propecia approved (1mg)
Low-dose finasteride approved for male pattern hair loss. Labelling at the time did not mention persistent effects.
FDA adds persistent effects warning
Labelling updated to state that sexual side effects "may persist after discontinuation".
FDA adds suicidal ideation to the label
Listed as an adverse reaction, not a warning — the FDA granted that part of a patient petition while stating the evidence did not establish that finasteride causes it.
MHRA strengthens UK warnings
Patient alert cards introduced for sexual dysfunction, depression and suicidal thoughts, and prescribers reminded that sexual effects may persist after stopping.
EMA confirms suicidal ideation as a side effect
After an EU-wide review, suicidal ideation was confirmed as a side effect of finasteride 1 mg and 5 mg, and a patient card warning about mood changes is now required in 1 mg packs. The EMA still concluded the benefits outweigh the risks for approved uses.
Key research
Independent researchers are uncovering the mechanisms behind PFS — without any known funding from Merck.
Melcangi et al. (2013–2024) — Neurosteroid alterations
Multiple studies from the University of Milan showing PFS patients have significantly altered neurosteroid levels in CSF, plasma, and feces. Neurosteroids regulate mood, cognition, and sexual function.
Csoka & Szyf (2009) — Epigenetic changes
Demonstrated that 5-alpha reductase inhibitors can cause persistent DNA methylation changes, explaining why effects continue after the drug clears the body.
Khera et al. (2014) — Androgen receptor overexpression
Baylor College of Medicine study showing overexpression of androgen receptors in penile tissue of PFS patients — the body's failed compensation for the drug's effects.
Melcangi et al. (2021) — Gut microbiome
Significant changes in gut microbiome composition in PFS patients, suggesting a gut-brain axis connection to neurological symptoms.
What prescribers are told, and what the evidence shows
Most clinicians are working from guidance that has not caught up. The gap is in the information, not in their intent.
What doctors say
"Side effects are rare and reversible."
What evidence shows
In 2011 the FDA required labelling to state that sexual side effects "may persist after discontinuation". A 2017 study found persistent erectile dysfunction in 1.4% of young men after a median of 205 days of use.
What doctors say
"It only affects a small percentage."
What evidence shows
With 7 million+ US prescriptions per year, even a 1% rate means tens of thousands of new cases annually. The FDA estimates that only 1–10% of adverse reactions are ever reported — meaning the true number of affected patients could be 10 to 100 times higher than the 21,287+ reports filed with WHO VigiBase across 153 countries.
What doctors say
"There's no proven mechanism for persistent effects."
What evidence shows
Multiple peer-reviewed studies have identified epigenetic changes, neurosteroid alterations, androgen receptor overexpression, and gut microbiome disruption in PFS patients. The research exists — yet to date, Merck has not publicly funded any of it.
What doctors say
"It doesn't affect mental health."
What evidence shows
In 2022 the FDA required suicidal ideation and behaviour to be added to finasteride's label — as an adverse reaction rather than a warning, and while stating the evidence did not establish causation. Depression, anxiety, cognitive impairment, and emotional numbness are among the most commonly reported persistent symptoms.
Current treatment landscape
An honest assessment of where things stand — and why there is reason for cautious hope.
Important: There is currently no FDA-approved treatment for PFS. No pharmaceutical company has funded research into treatment. All information below is based on independent research and patient-reported experiences.
The Milano Project — most promising avenue
Prof. Roberto Melcangi's research at the University of Milan has identified allopregnanolone — a neurosteroid depleted in PFS patients — as a potential therapeutic target. Animal studies have shown that allopregnanolone supplementation can reverse some finasteride-induced changes. This is the most advanced research programme and is funded entirely by patient donations through the Milano Project.
What some patients report
While no treatment is proven, some patients report partial improvement with lifestyle modifications. These are not recommendations — they are observations from patient communities:
- Regular exercise (particularly resistance training)
- Sleep optimisation and stress reduction
- Dietary changes (anti-inflammatory diets)
- Time — some patients report gradual, partial improvement over months to years
Caution: Be extremely wary of unproven treatments promoted online. Some interventions can worsen symptoms. Always consult a healthcare professional before trying any treatment approach. Visit our Support Library for evidence-based resources.
How to get help
You do not have to face this alone. Here is where to start.
WhatsApp support groups
Connect with other PFS patients in private, moderated groups. Share experiences and coping strategies with people who understand.
Join the patient registry
Add your case to the SIDEfxHUB registry. Your anonymised data helps researchers understand PFS and work toward treatment.
Report your side effects
Filing a report with your national regulator (FDA, MHRA, EMA) is critical. Low reporting rates make the drug appear safer than it is.
Support library
Research papers, patient stories, media coverage, and practical resources — all in one place.
Hear from PFS patients
Real patients sharing their experiences with Post-Finasteride Syndrome.
Mark's Story
Mark has been suffering with the devastating effects of finasteride for over two years.
Sam's Story
One pill destroyed Sam's life. He shares his experience with finasteride side effects.
20 Years of PFS
A patient who has been suffering from PFS for over 20 years shares his journey.
Sources & databases
All data on this page is sourced from peer-reviewed research and official regulatory databases.
FDA FAERS
The FDA Adverse Event Reporting System — the primary US database for drug safety reports.
Visit database →WHO VigiBase
The WHO global database of individual case safety reports — over 30 million reports from 153 countries.
Visit database →PubMed — PFS Research
Search peer-reviewed publications on Post-Finasteride Syndrome on the NIH database.
Search PubMed →PFS Foundation
The leading organisation funding PFS research, including the Milano Project with Prof. Melcangi.
Visit website →EMA — Finasteride Review
European Medicines Agency's safety review of finasteride-containing products.
View review →RxISK
Independent drug safety research organisation. Report side effects and access drug safety data.
Visit website →I think I have PFS. What now?
If you recognise these symptoms, here are 5 steps you can take right now.
Connect with others
Join a WhatsApp peer support group — talk to people who understand exactly what you're going through.
Report your side effects
Report to your country's health regulator. Every report makes these conditions harder to ignore.
Read about managing symptoms
Visit our Support Library for guides on coping strategies, talking to your doctor, and lifestyle approaches.
Join the registry
Register your experience anonymously. Your data supports research and helps prove the true scale of these conditions.
Think you have PFS?
You are not alone. Join the registry, connect with other patients, and help drive the research that could lead to treatment.