AN AMATEUR bodybuilder has told how steroid use wiped out his fertility and put him on course for a heart attack as a new documentary warns that the drugs are Glasgow's "hidden public health crisis".

Darren, a 35-year-old sales executive, has been injecting anabolic steroids on and off since around 2004 to improve his physique.

The Class C drugs are legal for personal use, but much of the supply comes from unregulated, underground production lines meaning there is no guarantee that they are safe.

Laboratory testing revealed that the actual testosterone concentration in the type Darren had been using was much higher than labelled, meaning he was unintentionally overdosing.

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Health checks also found that his testosterone levels were so high they could not be measured, his resting heart rate was twice what it should be, and that despite an otherwise healthy lifestyle he was at "massive risk of a sudden heart attack" - so high, in fact, that medics estimated his lifetime risk was 100 per cent.

"I knew there were going to be issues, but I didn't really expect it was going to come back saying I had a 100% lifetime chance of a heart attack," said Darren.

He is among the participants in a new BBC Scotland series, Laid Bare, which puts volunteers through a sort of living autopsy to predict what might kill them unless they change their habits.

Darren's case comes amid alarm over the rise in steroid use among gym-goers, which has been blamed on a 'Love Island' effect as men feel increasingly under pressure to achieve a muscular body.

In July, England's Local Government Authority - the umbrella body for councils - said the problem was an "emerging epidemic", with some council-run needle exchanges reporting that 40-60% of clients were injecting performance and image-enhancing drugs (IPEDs).

As well as steroids, some users are injecting synthetic tanning hormones.

John Campbell, who runs NHS Greater Glasgow and Clyde's needle exchange outlets, said he set up the city's first IPED clinic a decade ago after noticing a "real increase" in the number of people injecting steroids.

He said: "The reality is we have 6-7-8000 steroid and image-enhancing drug injectors in Glasgow and that would take it up certainly to the level of our heroin-injecting population, if not above that."

Injection also carries the risk of muscle abscesses if the product has been contaminated with bacteria during production in unregulated labs.

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Darren, who lives in West Lothian, said he noticed no ill effects until he and his partner began trying to conceive around five years ago.

"I was basically infertile for a while," he said. "My partner and I were trying for a baby and it just wasn't happening. I had a feeling I knew what was wrong so I had my sperm count tested.

"When it came back it wasn't zero but it was going to be pretty much impossible to get pregnant.

"It's reversible if you catch it early enough, but that's one of my concerns for these young guys that they're not going to come off it and cause damage to their reproductive system. Then when it does come time to settle down and have a family it's going to be too late."

Darren is now a father of three but it took the results of the Laid Bare testing to shock him into quitting steroids completely.

It also led him to abandon plans to enter bodybuilding competitions in April this year because he felt it would be "impossible" to compete.

Although doping is banned under International Federation of Bodybuilding and Fitness rules, unless contests are specifically branded 'natural' or 'drug-free' competitors are unlikely to be subjected to tests such as urine analysis and lie-detectors.

"You see a very big difference because very few people enter those," said Darren.

Affordability is also a lure. Darren said he used to spend more than £100 a month on protein powder and supplements, compared to £60 for his monthly steroid supply of 20ml.

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Dr Punam Krishnan, a Glasgow GP and presenter of the Laid Bare series - which also looks at shift working and Type 2 diabetes - said she was shocked at the scale of steroid use as it is not something she has seen much evidence of in her own practice.

"It's not something I was taught much about at medical school," she said.

"If anything, this case really highlighted to me the significant number of people who are using anabolic steroids, that it is an underground issue, and - worryingly - what are we likely to see in the next 10-20 years because there is an increasing trend in people using this?

"It is a Class C drug, but it is widely available in gyms.I think what this particular case study will demonstrate to people is that it is more common than we think it is, we probably all know someone who's using it, and that while in the short-term they make people look and feel good, there are so many adverse side effects."

Laid Bare is on BBC One Scotland on Thursday October 24 at 9pm