I've been on thyroid for years. At one point my doctor (who was not the doctor I had when I started on thyroid) decided to take me off the meds to get a baseline. I was supposed to be off a certain length of time, but before I reached that time I was so tired I could hardly walk across my classroom, came home each afternoon and went to sleep, and finally one weekend I slept all the way to our lakehouse 2-3 hours, got there and took a nap, got up and went to bed and continued this way all weekend, basically sleeping all the time.
My husband called doctor as soon as we returned home and he got me in right away. Apparently my thyroid had quit functioning at all. Hair loss, weight gain, lack of energy, dry nails and skin, shakiness, etc. are all symptoms. It is nothing to ignore and it can be treated easily in most cases!