Will thyroid replacement stop hair loss?

Maybe. If the hair loss is caused by hypothyroidism, then thyroid hormone replacement will stop the hair loss. Often time, the thyroid is not the cause of the hair loss. In that case, thyroid hormone replacement will not do much. You will know if you have thyroid problem through a blood test. If thyroid hormone is low, i would treat it to see if the hair loss will improve.
Maybe. I agree with dr. Nguyen. It is however important to remember that many people may have a thyroid problem and another reason for hair loss as well. So just because you have a your thyroid treated is not a guarantee that the hair loss will improve.
Possibly. If your hypothyroidism is the cause of your thinning hair, it would seem likely that medication would reverse or at least dismiss this tendency.