I did not even know I had Hypothyroidism (low thyroid) until I went into the Psych Ward about 7 years ago and my Pdoc tested and found it while my MD/GP had missed it all together. Since the Pdoc found the underactive thyroid I have been on Synthroid for all the years since. I know they test my TSH level and My T3 and T4 about evey 6months to monitor the dose between refills of the Synthroid.