I have experienced extreme hair loss over the past 4 years due to thyroid disease. You should mention it to your doctor. When I changed doctors my new one gave me Cytomel to help decrease the hair loss and so far it has; however, it is not growing back nearly as much as I had hoped for. It not only the thyroid disease that causes hair loss, sometimes it's the medication as well.
As for the Primrose oil, I gave that a try and didn't have any luck with it. But you may want to give it a try since so many people have reported that it worked for them.