The hormones that make men grumpy

Since the start of time, moody men have blamed their female counterparts for their grumpy demeanour. Now, however, women have been vindicated by scientists who have discovered that men are made miserable by their own hormones.

The grumpy condition - dubbed "irritable male syndrome" - is triggered by sudden drops in testosterone levels, which prompt men to become withdrawn and foul-tempered.

Dr Gerald Lincoln, of the Medical Research Council's Human Reproductive Sciences Unit in Edinburgh, said the hormonal changes could also produce symptoms that resembled a so-called "male menopause".

His findings came about after he studied the behaviour of male sheep. The rams' hormone levels soar during autumn and they rut. During winter, however, the hormone levels drop and they lose interest in mating. After studying eight rams, he found that a drop in testosterone levels caused them to lose confidence and become nervous, withdrawn and irrational.

Red deer, reindeer and Indian elephants also experienced similar hormonal mood swings, according to his research, which was published in the New Scientist. Similarly, Dr Lincoln found that when men who cannot produce testosterone came off hormone replacement therapy, they became irritable and depressed. He concluded the hormonal condition can affect men of all ages when stress causes the testosterone levels to fall. His findings were supported by hormone experts.

David Abbott, a reproductive specialist from the Wisconsin Regional Private Research Centre in Madison, said: "When a bloke gets grumpy and irritable, researchers try and explain it only in terms of cortisol levels and depression. They ignore that testosterone levels are probably also falling."

The research was backed by the example of sufferers of advanced prostrate cancer whose testosterone levels fall by at least 90 per cent after castration.