Choose organic, fermented soy over processed soy in cases of both hypo and hyper thyroidism. Limit soy, especially processed forms of soy like shakes, powders, soy milk and bars, and everything else it’s in – which is a lot. Read your labels.
Soy acts as both a goitrogen, and inhibits thyroid hormone absorption. You can either eliminate soy altogether, or limit it to organic fermented forms – like tempeh, miso, natto – in small quantities and not as a primary protein replacement. Non-organic soy is likely to be grown from genetically modified seed and sprayed with pesticides, so definitely needs to be avoided, by everyone.
It’s never a good idea to throw the baby out with the bath water though. Remember organic, fermented soy has many, many health benefits and is something I recommend to be included as part of a healthy and balanced diet by most people. If you’re umcomfy with this, then leave it out of course.