underactive thyroid
"I'm 19 years old, and I was diagnosed a few months ago. The only symptoms I had prior were constant fatigue. So luckily we discovered it early on in life. As soon as I started taking Levothyroxine, I was no longer fatigued, and I finally felt normal. 6 weeks after I started, my thyroid hormone levels were back to where they should be. Absolutely no side effects. This seems to be a very safe drug."