Thyroxine and iodine supplimentation??

For my Sister:

Currently taking one thyroxine daily.
She has a number of the symptoms of Hypothyroidism:

She is curios about Iodine supplementation.
The advise appears to be to slowly reduce the thyroxine as she supplements with iodine. And to reduce the amounts quicker if she experiences palpitations or nervousness.

Is there anything else she needs to be aware of at this stage.
Boron, Vit C and selenium would be part of her program.

Thanks T2.