Hello, I've been prescribed Synthroid for hypothyroidism. How much time after taking the pill is it safe to eat breakfast that includes considerable iron/calcium content (oat bran with yogurt)?

I have read that 1 hour after taking the pill should be enough for absorption, however, that multivitamins containing iron and calcium should only be taken at least 4 hours before or after. I have noticed that my usual morning cereal consists of 30 per cent iron (oat bran, which I actually take not to be constipated because of the extra iron I need to take in the evening)and calcium (in the form of yogurt). Would this influence the efficacy of the absorption of Synthroid?
Thanks very much.

Mrs. Pari