2023 – year in review

Fitness influencers and physicians raised alarms about risks of finasteride for hair loss this year, reaching millions of people through tweets, videos and podcasts. On the regulatory front, in France boxed warnings were added to finasteride packaging. Health Canada added a warning about suicidality while the UK regulator launched a safety review.

Forty-four relevant research papers appeared, including reviews addressing post-finasteride syndrome in the International Journal of Impotence Research and Nature Reviews Urology. Pharmacovigilance studies showed disproportionate risks of cognitive dysfunction and male-factor infertility associated with finasteride.

Details and additional developments follow.

Media & social media

Numerous men’s fitness influencers posted strong warnings about finasteride risks on X (formerly known as Twitter). A tweet from Noah Ryan has over 210,000 views as of this writing. A November 12 tweet from Andrew Huberman drew more than 1 million views. In April the Huberman Lab Podcast aired an episode with a segment on post-finasteride syndrome. Other podcasts followed: Dr. Ted Schaeffer and Dr. Mohit Khera on the Attia Drive Podcast and Dr. Michael Eisenberg on the Huberman Lab Podcast. Dr. Schaeffer provided the strongest warning by stating that post-finasteride syndrome is real, drug-related and can be permanent. In Italy, Roberto Melcangi, PhD discussed risks and harms of finasteride on the television show La Salute Che Viene (Health Rising).

Regulation

In May, French regulator ANSM announced the most significant regulatory change for finasteride in over a decade, in any country. In April, red boxed warnings began appearing on packaging of the 1 mg dose taken for hair loss. The warning states in part: “ATTENTION: This medication can lead to undesirable effects, notably sexual and/or psychiatric disorders.” A QR code links to an information packet which warns: “Side effects may persist after stopping treatment and in some cases for an indefinite period of time.” These changes reflect long efforts by French advocacy group AVFIN to alert ANSM to the drug’s risks. Organon, the current marketer of Propecia, took the drug off the market in France. The 1 mg dose remains available in generic form. An overview of regulatory activity in France may be found here.

Packaging of finasteride (1 mg) in France after a regulatory change ordered by ANSM, the national regulator.

Health Canada announced a “possible link between the use of finasteride & the risks of suicidal ideation and self-injury.” In the UK, the Medicines and Healthcare products Regulatory Agency (MHRA) launched a safety review of finasteride for hair loss, according to a March report in the Daily Mail.

On the Finasteride Watch website, the regulatory activity section was expanded and now includes separate pages for countries and regions from Germany to Japan.

In June, FDA held a Patient Listening Session on Post-Finasteride Syndrome, summarized here. The agency explains: “Patient Listening Sessions help the Agency inform medical product development, clinical trial design, patient preferences, and shape our regulatory thinking.”

Patient safety

Finasteride was included in the 2024 edition of Drugs to Avoid published by the French patient safety organization Prescrire.

Research

Forty-four relevant studies were published in 2023—the second-highest number ever. In an analysis of adverse event reports, Cho et al found a disproportionate risk of cognitive dysfunction linked to finasteride use. In another pharmacovigilance study, Baldini et al found a disproportionate risk of male-factor infertility which arises from semen and sperm abnormalities.

Post-finasteride syndrome seemed to be mentioned more frequently than in past years, with authors variously expressing concern or doubt. Given the accumulating literature, authors cannot dismiss the syndrome, but most are not ready to endorse it either. A post on Finasteride Watch took a “temperature check,” noting the level of denial in each paper.

Irwig et al assessed dermatologists’ beliefs and practices regarding adverse effects of finasteride, finding that just 18% believed the drug can cause persistent sexual side effects. A systematic review by Santana et al summarized effects of finasteride and minoxidil on male reproductive organs in animal studies. The prolific Melcangi lab published a review encompassing post-finasteride syndrome and post-SSRI sexual dysfunction. Da Silva et al reported striking effects of dutasteride on penile tissue in rats, including reduced cross-sectional area, increased connective tissue density and reduced smooth muscle density.

As in past years, papers in dermatology journals tended to downplay finasteride harms and overlook literature unfavorable to the drug.

Finasteride Watch website

On this website, the three most popular pages were a research review on alterations to penile and prostatic tissue, a page called ‘Weighing the risks of taking finasteride for hair loss’, and Andrew Huberman’s discussion of post-finasteride syndrome on his podcast. The ten most popular posts are listed here.

A distinctive feature of 5-alpha syndrome (post-finasteride syndrome) is genital numbness. ‘Seeking a medical sign of genital numbness’ explores techniques for observing this symptom as a sign.

The lost men’ reviews adverse events in early clinical trials which foreshadowed current concerns. Another post, among the most popular this year, reveals that finasteride is more disruptive of hormone signaling than commonly understood.

More firsthand reports of finasteride and dutasteride-related experiences were added. One compiles user reviews, while another gathers reports of men who used saw palmetto and stinging nettle, both natural 5-alpha reductase inhibitors.

The description of 5-alpha syndrome was rewritten for a general audience, with more details on disease course and a discussion of the limitations of diagnosis and treatment options.

A bibliography of research on birth abnormalities associated with 5-alpha reductase inhibitors was added.

In 2019 the Swiss dermatologist Dr. Ralph Trüeb published a notorious article proposing that post-finasteride syndrome is a delusional disorder linked to a personality disorder, and has published five other articles on the topic. This post critiques these papers and reveals conflicts of interest surrounding the journals where they appeared.

A special section called ‘The Partnership’ was added, documenting how physician-researchers supported the launch and marketing of Propecia and Avodart as ‘key opinion leaders.’ In exchange for promoting the drug, they received benefits such as research grants and co-authorship of articles with Merck and GSK researchers. Some also acted as paid consultants and speakers for the drug makers.

As noted earlier, a section on regulatory activity was expanded, now with separate pages for countries and regions.

Grey literature

A manuscript proposing an etiopathogenesis of 5-alpha syndrome, first published in early 2022, exceeded 800 downloads from the OSF preprint repository.

Summing up and looking ahead

In 2023 there was more frequent and pointed discussion of finasteride’s risks on social media and podcasts—not only by influencers, but prominent urologists and experts in sexual medicine. The latter appeared on the Attia Drive and Huberman Lab podcasts which are among the most popular in their categories. The strong warnings from men’s fitness influencers (including Andrew Huberman) reached at least a million people in venues popular among men aged 18–35.

There were no research breakthroughs and few original investigations, which is not surprising given the lack of research funding. Two pharmacovigilance studies linking finasteride to cognitive dysfunction and male factor infertility, respectively, indicated that researchers are exploring a broader range of harms by drawing on more than two decades of pharmacovigilance data.

Looking ahead to 2024, results of the UK MHRA’s safety review of finasteride are anticipated. Finasteride Watch will continue to monitor the literature and public discussions about risks and harms of finasteride. Notable developments will be tweeted at @FinasterideInfo.

See also: 2022 – year in review and a historical timeline.