A powerful hair-loss treatment being touted by influencers on TikTok may trigger erectile dysfunction and even suicidal thoughts, experts have warned.

Videos of young men proudly showing off their regrowth after taking the daily tablet dutasteride have racked up millions of views on the social media site.

Although dutasteride is not licensed in the UK for treating hair loss – it was developed to treat enlarged prostates – it can be prescribed off-label, meaning doctors can give it to any patient they believe may benefit.

But EU health officials recently issued a warning that the drug could trigger severe mental health problems, including depression and suicidal thoughts.

Earlier this month an inquest heard that a 31-year-old PE teacher had killed himself after starting a course of dutasteride that he had bought through an online pharmacy.

Sam Applegarth, from West Yorkshire, had struggled with premature hair loss since the age of 22 and he had tried other drugs without any side effects.

Mr Applegarth moved to Dubai last year and friends said he appeared to be enjoying life. His GP and family told the inquest that he had no history of mental illness or self harm and was a ‘bright and happy individual’. A post-mortem examination after his death on September 19 found no alcohol or illegal drugs in his system.

Sam Applegarth, from West Yorkshire, had struggled with premature hair loss since the age of 22 and he had tried some drugs without any side-effects

Experts are now urging the UK’s medicines watchdog, the Medicines and Healthcare Products Regulatory Agency (MHRA), to issue warnings about the serious potential downsides of dutasteride.

‘Dutasteride is a potent drug that can, in some cases, lead to unpleasant side effects,’ says Professor Penny Ward, a pharmaceutical expert at King’s College London. ‘Patients who start taking it need to know what worrying symptoms to look out for. If they begin to experience depression, they should see a doctor immediately.

‘Hopefully the MHRA will catch up with their EU counterparts soon and ensure that the drug comes with this warning.’

Dutasteride works by blocking the conversion of testosterone into dihydrotestosterone (DHT) – a hormone believed to cause hair loss by shrinking scalp follicles.

But experts warn that suppressing DHT can also trigger a range of debilitating side-effects.

Dutasteride works by blocking the conversion of testosterone into dihydrotestosterone (DHT) – a hormone believed to cause hair loss by shrinking scalp follicles

The drug is chemically similar to finasteride, one of the most widely used hair-loss treatments, previously taken by millions of men – including US President Donald Trump.

In 2024, the MHRA issued a warning about it, stating it could cause depression, low libido, erectile dysfunction and suicidal thoughts. While studies suggest around 4 per cent of patients experience these side effects temporarily, a small proportion – about one in 1,000 – report ongoing problems even after stopping taking it.

This condition, known as post-finasteride syndrome, can persist for months or even years. Dutasteride, however, is significantly more potent.

While finasteride reduces DHT levels by about 70 to 75 per cent, dutasteride suppresses more than 90 per cent. This means, on average, it leads to more hair regrowth but raised further concerns about the risk of lasting side effects.

A number of young men have taken to social media to show off the impressive results of taking dutasteride.

In one video, UK influencer Tom Gillbanks, who has more than 50,000 followers on TikTok, told how, after four months on dutasteride, he started to get ‘loads of thick hairs sprouting out of areas I never thought I’d get hair back’.

However, some studies have found that as many as 16 per cent of patients who take dutasteride experience sexual side effects.

It was found, however, that it does not appear to lead to side effects that continue after the treatment is stopped.

Experts say that, while unlicensed for hair loss, dutasteride is already widely used in the UK.

Sam’s GP and family told the inquest that he had no history of mental illness or self harm and was a ‘bright and happy individual’

‘Hair specialists use dutasteride frequently,’ says Dr Leila Asfour, a London dermatologist and chairwoman of the British Hair And Nails Society. ‘For most patients it’s a safe and effective drug, but doctors need to make sure patients are aware of the potential side effects.’

To limit the risk of complications, only certain patients should be offered dutasteride.

‘If the patient has a history of mental illness, then they shouldn’t take dutasteride,’ adds Dr Asfour.

Speaking at the inquest into the death of Mr Applegarth, leading hair-loss expert Dr Bessam Farjo, warned that it was ‘not difficult to get the medication online’.

He added that numerous online pharmacies were now ‘sprouting up’ to prescribe the drug to patients without seeing them.

Dr Asfour agrees, saying: ‘These online pharmacies do not necessarily check the medical history of the patient before prescribing dutasteride. And they do not always make sure patients are aware of the side effects to watch out for.’

Dr Stephanie Millican, the MHRA’s deputy director of benefit risk evaluation, says: ‘We have been monitoring this review of medicines containing finasteride and dutasteride and are now taking time to review the findings that were published last month.

‘Any potential updates to the product information for these medicines would be promptly communicated to patients and healthcare professionals, and appropriate steps taken to mitigate any identified risk.’

• For confidential support, call the Samaritans on 116123 or visit samaritans.org.