what if u were prescribed synthroid but u do not have a thyroid problem? what would it do to your body? im 32 yrs old an was told by my doctor that i have a thyroid problem..underactive. i was 121 lbs 2 mnths ago wen i started it an 8 weeks later i am 106lbs and i look very sickly. i believe i never had a thyroid problem to begin with. my height is 5 foot 6 inches. i look like a skeleton.