Hi, Welcome to HCM
It is usual to have abnormal cycle after removal of IUD. But you have hyperthyrodism , so it will better to do thyroid
profile and also USG pelvis, as it will rule out any other cause of abnormal cycle.
Dont go for D & C directly as it can damge uterine endometrium.
You can also wait for 2 to 3 more cycles , meanwhile complete your workup and then only think for D & C, as 6 month is usual time for normalisation of cycle.
Still have any doubt, let me know.