What happens when your TSH hormone is very low?

Hyperthyroidism. hyperthyroidism is what happens.
Two possibilities. The great majority of cases with low TSH are due to high thyroid hormone levels from hyperthyroidism or taking too much thyroid hormone. Rarely, a pituitary problem can lead to low tsh. In the first case, there will usually be symptoms of hyperthyroidism and in the second, symptoms of hypothyroidism.