There have been occasional discussions over whether it is possible to cure hypothyroid or hashimotos. Here is a case study of someone who states they have cured their hypothyroid illness with a number of aspects including a plant based diet amongst a number of things including a very high level of aerobic exercise.
No one here is recommended to give up thyroid medicine - and tbis is exactly what this lady did.
The traditional view is that hypothyroid cannot be cured.
I have taken on the message over aerobic training but not yoga or vegan diet. I feel there are some risks moving to vegan diet but will continue to explore further.