Doctors say a 45-minute epileptic seizure may have caused a transgender woman to revert back to being a man.

A new psychiatric study has described how an unnamed Australian man, aged in his mid 30s, had believed he was really a woman since he was four-years-old.

The patient received breast augmentations, hormonal treatment and facial surgery to appear more feminine in her mid-30s.

But after suffering the seizure, the transgender woman radically changed her mind about her gender - and her psychiatrist said it may be because the fit triggered biological changes.

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The unnamed man received facial surgery so he could appear more feminine (file photo). He did not have facial surgery

In a medical journal, psychiatrist Dr John Parkinson wrote: 'It may be that the prolonged seizure affected whatever biological structures serve to confer gender identity and personality structure'

'A firm decision was soon made to revert to male identity,' retired Wollongong psychiatrist Dr John Parkinson wrote in the latest edition of the medical journal Australasian Psychiatry.

Dr Parkinson said the seizure may have changed the 'biological structures' that gave the man his sense of gender.

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The man had not had surgery to his genitals.

However, he was out of money after spending so much money on breast enhancement surgery.

'A delighted mother came to the rescue and within six months the augmentation had been reversed,' Dr Parkinson wrote in the journal.

The epileptic fit caused further profound changes in the man's personality.

He stopped abusing drugs and alcohol and no longer showed signs of suffering Borderline personality disorder, the study said.

The man had suffered a brain injury when he was younger but Dr Parkinson said that had 'affected neither personality nor gender identity.'