Hi,
As with any new supplements, it is always advised you start with MINIMAL dosage. I would be worried if you were taking synthetic supplementations, but superfoods is not a "supplement", and is a wholefood, so it is much safer than any synthetic, concentrated isolated, and/or standardized drugs or herbs. Wholefoods most likely will not cause any sort of "imbalance" to the body, as all of the nutrients in superfoods are assimilated within seconds of ingestion. And since superfoods come with a whole variety of healthful ingredients, and is not just concentrated "dulse", it is most likely safe for hyperthyroid.
But to be on the safe side, start with a smaller dose and note how you react, then you can decide if it's good for you or not.