I've put together the information from several sources.
Several sources suggest that a low ratio of Testosterone to SHBG can be a factor behind Gyne. I myself have a poor ratio.
I have come across several sources that state that Nettle extract does not increase Testosterone or decrease SHBG. What it does, apparently, is bind to the SHBG instead of the Testosterone doing it. This leaves you with more free Testosterone. But unlike hormone therapies it does not actually increase your overall testosterone levels (which can cause problems of course).
I have come across this usage of nettle extract (listed amongst other benefits) on Herbal sites. But I have come across it being touted specifically for its binding to SHBG on fitness and bodybuilding sites. Obviously it is in their interest to free up testosterone.
I found it interesting and given that it has not recorded side effects it seems worth a try. I will certainly have a go.
Just wanted to see if anyone else had heard of it.