Your question is a good one which I can't answer with absolute certainty. I hope others who participate in these forums can.
I, too, am hypothyroid and enjoy eating cruciferous vegetables. I, too, have read allegations that a substance(s) from these vegetables binds with the receptor sites for thyroid uptake preventing absorption of the thyroid hormones. I've also read that when enough time separates the taking of thyroid medication and the ingestion of the vegetables, no harm is done. So what I do, right or wrong, is take my thyroid medication when I first arise in the morning (best on an empty stomach for maximum absorption), and then eat my cruciferous vegetables in the evening. Given the choice, I'd probably give up the thyroid medication before I'd give up my vegetables. Hope this information is helpful and hope you will share any new knowledge you learn, at this forum.