The Hair Trade

Sections

1. What people mean by post finasteride syndrome
2. The trial numbers answer a different question
3. The brain steroid theory
4. A normal testosterone test doesn’t settle this
5. The epigenetic theory
6. Expectations can matter without explaining everything
7. If your symptoms haven’t gone away
8. When to call your doctor
9. Where my 5 mg prescription fits
10. Other options for your hair
11. How to use this page
12. Sources

Keeping your hair is a reasonable goal. So is wanting to know what could happen to your dick.

Finasteride can help you hang on to your hair, and some guys grow some back. You don’t need to apologize for preferring that to watching it go down the shower drain.

Give it a few months before judging the result. If it helps and you want to keep that benefit, you’ll need to keep taking it, so work that into the decision before you start.

What people mean by post finasteride syndrome

The harder conversation starts when stopping doesn’t put things back. Some guys say their sex drive, erections or orgasms still aren’t right months after the last pill. Others report mood changes or trouble thinking clearly. People call that post finasteride syndrome, or PFS. Giving it a name doesn’t mean we know what’s actually going on. [3, section 6.2] [13]

Don’t write off sexual problems that keep going after stopping. The U.S. drug label lists those reports. It also says voluntary reports don’t reliably tell us how often it happens. They don’t always establish whether the drug caused it, either. Take the reports seriously and look at what the researchers actually measured. Just don’t pretend we’ve already got one proven explanation for everybody. [3, section 6.2]

The trial numbers answer a different question

The table counts sexual problems reported as drug related in the first year of the 1 mg trials. Those trials had 945 men on finasteride and 934 on placebo. Keep that specific question in mind when somebody quotes them at you. [3, section 6.1]

First year of the 1 mg trials: sexual problems reported as drug related

Reported problem	Finasteride	Placebo
Lower sex drive	1.8%	1.3%
Erection problems	1.3%	0.7%
Ejaculation problems	1.2%	0.7%
One or more of these problems	3.8%	2.1%

96.2% on finasteride didn’t report those listed sexual problems in the first year. I’d call those pretty damn good odds, with a 1.7 percentage point difference from placebo. Don’t add the rows together; one guy could report more than one problem. And don’t stretch a first year count of listed problems into every possible side effect for every year you take it. [3, section 6.1]

That 3.8% isn’t the PFS rate. Neither is the percentage still symptomatic in a study that deliberately recruited men whose symptoms hadn’t gone away. Irwig followed that selected group, not everybody collecting a first prescription. You can learn what happened to those men without pretending it tells the next guy his odds. [6]

The brain steroid theory

Finasteride blocks an enzyme that helps make DHT from testosterone. The same enzyme helps make other steroids, including ones that affect the brain, called neurosteroids. Researchers are also looking at those other steroids in men whose symptoms haven’t gone away. [9] [1]

A few small studies checked the fluid around the brain and spinal cord in men who’d stopped finasteride but still had symptoms. They found differences in steroid levels. One early pilot had just three affected men and five controls. The blood results didn’t simply match the fluid results. Changed steroid production could help explain the symptoms, but measuring it after somebody gets sick doesn’t show whether the drug caused the change. [9] [10]

That’s something worth researching. It isn’t a reason to get a spinal tap or pay for a “neurosteroid reset.” These weren’t treatment trials, and they didn’t establish a diagnostic PFS test. Somebody selling the reset has skipped a few steps. [9]

A normal testosterone test doesn’t settle this

Another idea is that the tissue responds differently to hormones even if the blood level looks fine. A small study compared foreskin from eight symptomatic former users with samples from eleven men who hadn’t taken finasteride. Some cells in the symptomatic group had more androgen receptor staining; nerve density didn’t differ. That’s what they measured. [11]

A finding in foreskin doesn’t prove the drug permanently changed the receptors or caused the symptoms. They didn’t have anybody’s samples from before treatment, and the controls were getting circumcised for a tight foreskin. Two affected men had also been in an earlier steroid study. You can’t count every paper as a whole new group of patients. [11]

Basaria’s group compared symptomatic former users, former users without sexual symptoms and men who’d never taken it. Blood testosterone and DHT didn’t separate them, and neither did the skin measures of hormone action they checked. So “everybody just needs more testosterone or DHT” doesn’t fit those findings. That still doesn’t settle what happened in the brain or make the symptoms imaginary. [13]

The epigenetic theory

Epigenetics is about changes in how genes get used, without rewriting the DNA letters. In one pilot, a chemical mark on a gene involved in making the enzyme finasteride blocks appeared more often in spinal fluid from symptomatic men than controls. The blood samples didn’t show that difference. [12]

That study enrolled sixteen patients and twenty controls, with spinal fluid from thirteen controls. The authors couldn’t tell whether the mark came before treatment or after it. It gives them something specific to test next, not proof that finasteride changed a guy’s hormones for good. [12]

Expectations can matter without explaining everything

In another study, men taking 5 mg for an enlarged prostate reported more sexual side effects if they’d been warned: 43.6% versus 15.3% among those who finished. Everybody took finasteride, there was no placebo group and they didn’t follow persistent symptoms after stopping. Include those details when you talk about the study. [14]

What you expect can affect what you notice and report. That’s no excuse to hide side effects, and it doesn’t prove the guy whose dick still won’t work months later imagined it. They studied reports during prostate treatment, not PFS after hair treatment. Don’t use one study to answer a different question just because you’d like the argument to be over. [14]

If your symptoms haven’t gone away

If your symptoms haven’t gone away, tell your doctor what’s changed and ask for help. You don’t need to win the fight about the syndrome’s name first. Treat the problem you’re having. [1]

Write down the product, dose, when things changed and what happened after you stopped. Add your other prescriptions and supplements. The appointment goes better when you aren’t spending half of it trying to remember which month your sex drive packed up.

These studies don’t give us a test to diagnose PFS or a treatment that reverses the whole syndrome. They don’t tell you how long your symptoms will last, either. Be careful with the person who turns a research finding into a guaranteed cure and then sells you the hormone or supplement package. None of these mechanism studies tested the package. Before paying, ask where they actually tested the package they’re selling you.

When to call your doctor

• Depression or suicidal thoughts while taking it: UK MHRA advice for the 1 mg tablets is to stop finasteride and contact your clinician as soon as possible. For 5 mg finasteride or dutasteride, it says to contact the clinician promptly. [7]
• Lower sex drive or changes in erections or ejaculation: talk with your prescriber about what to do. The advice about stopping for mood changes doesn’t automatically apply to every side effect. [7]
• Breast lumps, nipple discharge, or a serious allergic reaction: get medical attention. Trouble breathing or swelling of the tongue or throat needs emergency help. [5]
• Immediate danger from suicidal thoughts: get emergency help now. Don’t wait for a refill message or a routine appointment.

That stopping advice depends on the dose and comes from UK guidance. The labels aren’t identical in the U.S. MedlinePlus also says to call a doctor immediately for new or worsening depression or thoughts of self harm. [4] Say what changed and when. Happening after a pill doesn’t by itself prove causation, and stopping doesn’t guarantee everything goes back.

Where my 5 mg prescription fits

I usually prescribe 5 mg daily because it often costs less. The 1 mg tablets for hair loss can cost a lot more than the 5 mg tablets sold for an enlarged prostate. I weigh that cost against the side effect risk, and 5 mg often makes more sense to me. The approved hair dose hasn’t changed just because I make that choice.

The FDA approved Propecia dose for hair loss is 1 mg daily. Using 5 mg for hair loss is off label, and the trial numbers above belong to 1 mg, not 5 mg. Take your prescribed dose, with or without food. Don’t quietly swap doses because somebody quoted a table. [3, sections 1, 2 and 6.1]

Read the finasteride reference page for the usual medication instructions. Here we’re dealing with what those instructions don’t settle: symptoms that stick around and the different attempts to explain them.

Other options for your hair

Dutasteride’s another option, and I actually prefer it for hair loss. That’s off label in the U.S., and it can cause sexual side effects too. [8]

It also isn’t a PFS treatment claim. Dutasteride works on the same enzyme family, and the research here doesn’t show that switching reverses persistent symptoms.

Topical minoxidil is another FDA approved choice, with finasteride or by itself. It can irritate the scalp and doesn’t work for everybody. You can also discuss transplantation with somebody who’s actually assessed your hair loss. [2]

Read the minoxidil page if you’re considering it. Leaving your hair alone is an option too, if the loss doesn’t bother you. It’s your head and your treatment decision.

How to use this page

If a study recruited men whose symptoms never went away, read it as research about those men. It might give us something useful to investigate, but a guy who’s starting his first prescription can’t get his odds of joining them from that study. A normal testosterone result doesn’t make your changed symptoms disappear, and a research abnormality doesn’t come with a ready made treatment.

Bring the timeline and name the problem. Trouble getting hard, no interest in sex and a mood change aren’t interchangeable. Get help with the one you’re actually having instead of trying to settle the entire internet fight in a single appointment.

Sources

1. NHS. Common questions about finasteride.
2. American Academy of Dermatology. What is male pattern hair loss, and can it be treated?
3. PROPECIA prescribing information. DailyMed, sections 1, 5.2, 6.1 and 14.1.
4. MedlinePlus. Finasteride drug information.
5. NHS. Side effects of finasteride.
6. Irwig MS. Persistent sexual side effects of finasteride: could they be permanent? J Sex Med. 2012;9(11):2927–2932. PMID 22789024.
7. MHRA. Finasteride and dutasteride: updated safety warnings. May 11, 2026.
8. DailyMed. Dutasteride capsules: U.S. prescribing information, sections 1 and 6.
9. Melcangi RC, et al. Neuroactive steroid levels and psychiatric and andrological features in post-finasteride patients. 2017. PMID 28408350.
10. Melcangi RC, et al. Neuroactive steroid levels are modified in cerebrospinal fluid and plasma of post-finasteride patients. 2013. DOI10.1111/jsm.12269.
11. Di Loreto C, et al. Androgen receptor and nerve structure density in human prepuce after finasteride. PLoS ONE. 2014;9:e100237.
12. Melcangi RC, et al. Altered methylation pattern of the SRD5A2 gene in the cerebrospinal fluid of post-finasteride patients: a pilot study. Endocr Connect. 2019;8:1118–1125. PMID 31272082.
13. Basaria S, et al. Characteristics of Men Who Report Persistent Sexual Symptoms After Finasteride Use for Hair Loss. J Clin Endocrinol Metab. 2016;101:4669–4680. PMID 27662439.
14. Mondaini N, et al. Finasteride5mg and sexual side effects: how many of these are related to a nocebo phenomenon? J Sex Med. 2007;4:1708–1712. PMID 17655657.