If your TSH is around 5, you are not in the normal range. This is why your hair is falling out. You are still hypothyroid and need an increase in your Synthroid dose. Synthroid's official website (www.synthroid.com) states that the treatment goal is to keep your TSH between 0.3 and 3. This follows the recommendations of the American Association of Clinical Endocrinologists. Your doctor/lab is probably using the old recommended upper limit of of 5 or 6 in decided what falls into the "normal" range. Show your doctor this info and tell him you want to get your TSH below 3 (below 2.5 is better). Other tests would be free T4 and free T3, but based on TSH alone, your dose needs increasing.