Gynaecomastia is a condition, not an illness. It's simply the medical term for excessive development of the breasts in men. If you've got man boobs then you HAVE got gynaecomastia because that's what the word means!
So it's likely that you've got a minor hormonal imbalance, which is fairly common in people who're overweight and with people who over-indulge in alcohol (amongst other causes). Simply getting older can also be a factor
http://www.nhs.uk/chq/Pages/885.aspx?CategoryID=61
Since it's not an illness then, unless the condition is particularly causing you problems in some way, there's no need for any treatment.