I am reading a few thyroid books right now... and in one of them (I believe the Thyroid Solution?) the author says that even a slight inbalance of hormones as a result of an issue with your thyroid can cause repeated miscarriage and infertility. (however, if your thyroid is balanced, the author said it was possible to carry a healthy pregnancy)
I had a miscarriage about a year ago, and had been dealing with infertility about 6 months before that, and I am willing to bet my thyroid is to blame. Unfortunately, I have like 3 seperate dr's, and they don't really communicate well.
So I don't know if I will ever really KNOW if my thyroid had a hand in it, but I am seeing an endocrinologist in a few weeks who will hopefully help me sort through all this.
That's about all I know, and it isn't much!
Hope it helps!