Yes some people take 50 mg , and they tolerate it. But it's really unnecessary to take that much as thyroid gland only contains approximately 20 mg of iodine. It has quite big reserve and one can go quite long without iodine. About 80 mcg is used daily based to make thyroid hormones. Rest of your body requires some milligrams of iodine, 50 mg is just not necessary for long term.
Sure you could go up to 50 mg but as you have existing thyroid malfunction it's not recommended!
For someone who is only deficient to iodine 50 mg might not be an issue as they have no thyroid issues yet. For them 50 mg usually causes transient hypothyroidism , TSH rises but it passes once iodine is reduced.
Yes 50 mcg is little, but it's better to start low and increase slowly to avoid side effects and possible thyroid malfunction.
800 mcg to 1100 mcg is basically safe amount and tolerable in most studies. It also fills up storages relatively safe.
I for example developed awful cough after four months on iodine , I went too fast up to 500 mcg. My lungs were irritated for 6 months.
Took me a year to start adding a bit iodine back to my diet and now it goes ok except it doesn't help my thyroid much.
As your thyroglobulin antibodies were negative your thyroglobulin level could be tested. At this point it seems only ZRT lab does thyroglobulin and iodine test. I have done it three times. It's finger prick test for thyroglobulin and 24 urine for iodine, not loading test. It only reflect consumption of iodine during past few days so it's a good test to determine how much iodine your diet contains. It also measure mercury, arsenic, cadmium and bromine.
I see so many people going wrong with high dosages of iodine, for some it resolves without harm for some it starts an episode of hell. We can forget all genetic factors affecting how iodine is handled. Maybe for some high dosages are ok or even needed because of genetic mutations. Or maybe for rest of us high dosages are problematic because of genetic mutations even though our bodies would be crying for iodine.
That's why I recommend careful experimenting.