A study has found a four-fold increase in the number of men in Sydney's south-east who have been diagnosed with throat infections caused by gonorrhoea.

The research published in the Medical Journal of Australia has been examining the number of cases of the sexually-transmitted infection between 2010 and 2012.

Almost 90 per cent of patients with gonorrhoea were men and those with related throat infections jumped from 87 to more than 350.

Professor Mark Ferson from the South Eastern Sydney Local Health District says more work will now be done to try to determine why there has been such a rise.

"That's been the big increase there," he said.

"We can't explain that at this stage ... so the next steps are to enhance the surveillance.

"We are writing to doctors to find out why the tests were done, what the person's risk factors [were], what their sexual behaviour was."