MUSCLEMEN who pump iron are more likely to go bald, scientists warn. They have discovered bodybuilders’ testosterone soars after a weights session ? and that turns into a toxic substance which attacks hair follicles. The research reveals fellas who lift weights just three times a week for 45 minutes over two years are heading for a premature slaphead. Boffins found testosterone levels soared an average 25 per cent after one of the sessions. They returned to normal after 30 minutes when the body converted the male hormone into a chemical called DHT. But DHT, or dihydrotestosterone, shrinks follicles and roots ? so hair grows back thinner each time. It is the biggest single cause of baldness other than genes. Beefy blokes who had a high-fat diet were found to be at greatest risk of the balding hormones. Women who lifted weights suffered the same side-effect. Last night hair transplant specialists Rogers Medical Group said: “We have seen an increase in men in their twenties and thirties who regularly circuit train. There’s no doubt it is often a factor in hair loss.”