I am very puzzled by the idea that a TSH that is low is any cause for concern in the absence of other “out of range” tests. TSH is a hormone that is produced when there is a need for more T3,T4, etc. If none of the thyroid hormones are higher than they should be, TSH levels should be low. Too low of a TSH can happen when levothyroxine is too high, as in Grave's disease. That is because high thyroxine levels suppress the production of thyroid stimulating hormone (TSH). TSH is high in Hashimoto's thyroiditis or when dietary iodine is inadequate because TSSH (thyroid stimulating stimulating hormone) is produced in our bodies valiant efforts to increase our production of thyroid hormone.
I was taught that the range commonly used for normal is probably skewed a bit and the true normal for people who actually have no thyroid issues is probably a bit lower than the “official” normal. In other words, if your TSH is a bit lower than the normal, you are fine, but if your TSH is a bit higher than the normal, you probably need treatment.