underactive thyroid
"The first two days of taking the medicine, I experienced body aches all over, headaches, thus, I took aspirin in the evening to try to alleviate the pain.  The third day and beyond, I felt/feel more energized, no headaches, no backaches, mental clarity, and just relieved.  I say you have to give the medicine time to kick in and get in your system. I am thankful."