Can a thyroid problem cause irregular period?

I've always had irregular periods since i got them ....i found out last Jan07 that i have endometriosis then Feb to July 07 went through lupron treatment to help the endometriosis so i could get pregnant....then doc said i would get period on my own again after shots but almost 2 months went by so he gave me provera...that month i had to take 2 rounds of provera cause it didn't work first time...then every month have to take provera to have provera....and clomid...i took provera almost 2 weekd ago and still no period ....so i am going to see specialist on Jan 15 to get help...i was wondering do u think i could have a thyroid problem?