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Published 12 June 2009

Fungus may have a role in triggering sex change in some animal's sex and could explain why some athletes produce higher than normal readings.

Scientists have discovered they contain an enzyme which generates steroid hormones including the most common of male sex hormones testosterone.

Dr Christy Hunter (pictured right) of the University of Brighton said the triggers for sex change in mammals and some amphibians like frogs have until now generally remained unexplained, but contact with fungus-produced hormones in the environment could be a key factor.

He said it was unlikely to explain why the sexuality of humans sometimes changes – that is more likely to be due to genetics – but, he said, an athlete coming into contact with these hormones might see higher readings of testosterone in doping tests.

And it probably explains why some lower forms of animals change sex. There are more than 1.5m species of fungus globally including mould, yeast and toadstools, but only 7,400 species have been investigated.

Dr Hunter said: "Even if just a few contain this enzyme it could represent a significant biological machine for generating androgens (steroid hormones) and causing sex change in animals."

Dr Hunter discovered that the fungus converts a steroid compound present in the environment when animals die and decompose into male sex hormones. He is now investigating the level at which this phenomenon is operating in the environment.

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