Hey... Strangely I think I've never wondered about that. I'm a man and I've had gynecomastia when I was a teenager. I took Tamoxifen wich is an antagonist of the estrogen receptor in the breast tissue. It work a little but I ended up having cirurgy to reduce my breast. Not much after that my pains started. I've seen that they are relating estrogen to CFS/ME and FMS. (http://simmaronresearch.com/2014/12/age-patterns-mecfs-hormones-autoimmunity-viruses/) I wonder if anyone have more info on that!? Could I have messed with my estrogen levels?