Nipple discharge in men
I am a 29-year-old dude in good health. I started having nipple discharge when I was 12 and didn't realize at the time that it was abnormal. The discharge is watery/milky in color and smells actually a bit like breast milk. It's always been a bit cyclical but it started to increase recently, so I went to a doctor and got a referral to an endocrinologist. He ordered a pituitary hormone panel and everything was pretty much normal. Testosterone was in the upper half of normal range, estrogen at the very upper end of normal range, prolactin normal, beta-HCG only slightly above normal. The endocrinologist said he didn't have any more ideas on what could be causing it and didn't think it was galactorrhea because of the low prolactin levels.
I want to emphasize that it isn't really a problem (certainly weird though); I'm just addressing it more out of curiosity.
The only medications I take are metoprolol and zolmitriptan, both for migraines.
I know nipple discharge can be a symptom of breast cancer; but considering that I've had this for 17 years, I think I would have died by now if that was the underlying cause. It can also be a sign of infection; but there is no inflammation and a 17-year nipple infection seems really unlikely.
I'm asking on here because I've already run all over the internet trying to find information. Almost all of the information concerns women, and the information on men relates to medication side effects or breast cancer. Could this just be idiopathic nipple discharge that isn't a symptom of a deeper problem? Anyone have advice on the next step to take after the endocrinologist?