Moody men now have a name for their version of PMT: irritable male syndrome. Researchers in Edinburgh, working from studies of sheep, believe men's brains react in a similar way to women's to fluctuations in the sex hormones.

Dr Gerald Lincoln, a researcher at the Medical Research Council's human reproductive sciences unit in Edinburgh, said the effect of fluctuations in testosterone levels are wide reaching, spanning beyond the popular connotations of sexual functioning.

A lack of testosterone can make a man's energy levels decrease, said Dr Lincoln, making some men increasingly moody and depressive.

While Dr Lincoln's research focused on male sheep, a species that has very distinctive annual sexual seasons, he believes the same effects are found in humans. "The best example is to look at men who receive hormone replacement because they produce insufficient levels of testosterone. When they stop their treatment, or are given a placebo, the irritable symptoms become very pronounced," he said.

The research proves men and women's moods react in the same way to fluctuations in their hormones. Women's hormonal moods have been more traditionally recognised because of their monthly and life cycles, the source of most fluctuations.

Dr Lincoln said the research in animals proves that stress is the biggest external influence over the sex hormones. "If there is a stressful situation at work, or a person has been in an accident, or an emotional situation, or has been taking drugs, hormone levels can fluctuate. These fluctuations are far more profound than we tend to realise.

"While PMT, menopausal, and post-baby blues are all recognized as withdrawal hormone states, men have not had the same recognition."

Dr Lincoln went on to say that once the chemistry of male hormones is better understood, it would be more likely that a treatment could be developed. But for now, he said: "I think the important thing is to recognise the phenomena, then we can think about treatment".