Image source, Getty Images

By Ella Rule

BBC News

"Dangerous" muscle-building drugs are being sold illegally in shops around the UK, a BBC investigation has found.

The substances, known as Sarms, can cause erectile dysfunction, mood swings and liver problems, doctors warn.

Secret filming by the BBC found they were widely available in shops that sell bodybuilding supplements as well as online.

Responding to the findings, the Royal Pharmaceutical Society (RPS) called for the law to be tightened.

Sarms - which stands for selective androgen receptor modulators - are body-enhancing drugs that mimic the effects of anabolic steroids, which increase muscle mass and strength.

The Food Standards Agency (FSA) says they are categorised as an "unauthorised novel food" that "should not be consumed". It adds that "placing them on the market in the UK is a criminal offence".

Originally developed as an experimental drug to treat muscle-wasting conditions, they have become popular with gym-goers on social media who want to build muscle and lose fat.