Finasteride, a hair-loss medication reportedly used by footballer Wayne Rooney, 'could cause permanent impotence and shrink genitals in some men' says the Daily Mail.
The story is based on two sources. The first is a US TV interview with a man who claimed his genitals shrunk after taking Propecia (finasteride), a drug used to treat male pattern baldness. The second, more verifiable source, is a study that found that finasteride could cause persistent loss of libido and erectile dysfunction.
There are a number of significant concerns with both sources. Firstly, there is no hard evidence to back the claims of the man who was interviewed. And the second study included only a very small sample of men, all of whom were experiencing persistent sexual problems, and who were recruited via a website that was set up by men who claimed that finasteride had caused them sexual side effects.
This may not necessarily reflect the experiences of all men who take finasteride.
While the manufacturers of Propecia concede that loss of libido and erectile dyfunction are known side effects of the drug, they report that these types of side effects are uncommon (clinical trials have observed frequency of 1.8% for loss of libido and 1.3% for erectile dysfunction).
Although the study cannot tell us how many men experience persistent problems after taking finasteride, it does highlight how important it is for doctors who prescribe finasteride for male pattern baldness to ensure that men are fully informed of the potential adverse effects upon sexual function.
Where did the story come from?
A single author from The George Washington University, US, conducted this research. The study reports no sources of funding so it is unclear whether there could be any potential conflicts of interest.
The study was published in the peer-reviewed Journal of Sexual Medicine.
The Mail’s headlines are incredibly alarmist and do not take into account the important limitations of this study – principally that it only followed a small self-selected sample of men already experiencing persistent problems for an extra 14 months. How many men who take the drug experience persistent problems is not known. To cap it all off, the claims that Wayne Rooney has ever taken Propecia are pure speculation by the media.
What kind of research was this?
This was a small cohort study designed to follow up men who were experiencing persistent sexual side effects after taking finasteride to tackle male pattern baldness, to see how their sexual dysfunction would change over time. The researcher wanted to examine whether sexual side effects would resolve, improve or remain diminished.
Finasteride is a drug that blocks the metabolism of testosterone (i.e. it is an anti-male-hormone drug). It is licensed in the UK to treat benign (non-cancerous) prostate enlargement, and a lower-strength version is also licensed to treat male pattern baldness. It is known to have sexual side effects including decreased libido, impotence and ejaculation disorders.
This study reports that other clinical studies of men who have taken the drug for male pattern baldness have found that sexual side effects may persist for years after stopping the drug. This research aimed to see whether this was the case. However, as this study has followed only a very small sample of men, all of whom experienced continued problems in the months following stopping the drug, it can’t tell us what proportion of all men who take the drug experience sexual problems, or what proportion of men experience problems in the months or years after stopping the drug.
What did the research involve?
The study included 54 men aged less than 40 years who had taken finasteride for male pattern baldness and who experienced sexual side effects that persisted for at least three months after stopping the drug. The men had taken part in a previous study examining persistent sexual side effects of finasteride and most of these men had been recruited to that study from an internet forum dedicated to unresolved side effects of finasteride. The author had excluded men who had reported sexual dysfunction, and chronic medical or psychiatric conditions prior to taking finasteride.
In the initial study, interviews with the men had been conducted via telephone or Skype (an internet videophone system). This study performed further follow-up of the men for 9-16 months (average 14 months) via email. Sexual function was assessed using the Arizona Sexual Experience Scale (ASEX), which consists of five questions that measure core elements of sexual function:
- erectile function
- ability to reach orgasm
- orgasm satisfaction
Each question was assessed on a 6-point Likert scale ranging from high function (scoring 1) to low function (scoring 6). Sexual dysfunction was diagnosed if the total score was 19 or above, or if any one question scored 5 or more, or if any three questions scored 4 or more. The ASEX is said to have been previously validated through assessment of 16 healthy men who had average scores of around 2 for each question. It’s understood that the ASEX scale could be administered regardless of a subject’s sexual orientation or the availability of a sexual partner.
What were the basic results?
At the time of the original interviews, the average age of the men was 31 years and the average age they had started taking finasteride was 26 years. The majority of men were white (80%) and heterosexual (94%). The average time they had taken finasteride was 23 months.
At the time of the first interviews, the duration of persistent sexual side effects was:
- 3-6 months for 7% of men
- 7-11 months for 9%
- 1-2 years for 44%
- 3-5 years for 19%
- 6 or more years for 20% of men
The mean total ASEX scores were 7.2 before taking finasteride, 22.2 after taking finasteride at the time of the initial interview, and 20.8 at the time of the current reassessment, an average of 14 months later. Sexual side effects were still present at reassessment in 96% of subjects, and 89% of subjects met the definition of sexual dysfunction. Persistence seemed to be independent of the duration of finasteride use or duration of problems after taking finasteride.
Additional symptoms that men volunteered, aside from the ASEX scores, were:
- change to semen quality and volume (11%)
- a change in penis size, curvature or reduced sensation (19%)
- decrease in spontaneous erections (9%)
- a change in testicular size, or testicular pain (15%)
- a change to mental abilities and/or depressive symptoms (17%)
How did the researchers interpret the results?
The author concludes that men who developed persistent sexual side effects after stopping finasteride to tackle male pattern baldness still had sexual dysfunction months later.
This study provided an additional 14 months follow-up of 54 healthy young men who had experienced persistent sexual side effects in the months or years after taking finasteride to treat baldness. At the time of reassessment, 96% still had persisting problems, with most meeting the criteria for sexual dysfunction.
The findings will not be all that surprising to doctors, because finasteride is known to cause side effects of decreased libido, impotence and ejaculation disorders. The problem is that this study still can’t reliably answer the question of how many men suffer these problems, and for how many of them the problems persist in the longer term. Problems with the study include:
- The study only included a very small sample of men. The original sample was 54 men, and the author says that 81% participated in reassessments – presumably only 44 men, though this is not clarified in the report.
- All of these men experienced persistent problems in the months or years after taking finasteride. The research cannot tell us overall what proportion of men who take finasteride for male pattern baldness will experience persistent sexual side effects after stopping the drug. We also don’t know what proportion of men experience sexual side effects while actually taking the drug.
- The study has also not explored whether these men could have had another unidentified medical or psychological factor that was influencing their problems.
- The results cannot tell us how many men who take finasteride for benign prostatic enlargement experience persistent sexual side effects.
While the study cannot tell us how common persistent sexual problems are after taking finasteride, it does highlight how important it is to ensure that men are fully informed of the potential adverse effects of this drug upon sexual function.