So I got motivated to do some research today. What I wanted to find out was the correlation between myostatin and steroid gains when off cycle, when, instead I came across an article and study on hcg and sperm production. This article didn't answer my original question but it is a good article explaining the use of hcg (even though no one tapers off anymore). Also at the bottom of the page it talks about diesel fuel exhaust and estrogen which I had no idea about, but doubt it will make much difference. It had some interesting stuff in it.
Though I'd share it so if your bored give it a glance it's a good read

http://www.ironmanmagazine.com/index.cfm?page=article&go2=1090