#159--Are you allergic to your thyroid medication? Synthroid contains MILK! Armour Thyroid contains CORN! And they all contain binders, colorings, and other additives. And whatever the medication, the truth is you are likely treating a symptom and not the true etiology of the problem.
The thyroid will often down regulate in people who are overly stressed in an effort to keep the body from literally burning the candle at both ends. And that stress can (and often does) come from exercise. Your body's need for survival trumps your ego's need for washboard abs. So if the level of stress you're experiencing increases above a given threshold--and that threshold is different from person to person and even from day to day--then your exercise program can be seen as a threat to the system. To survive, the body will slow down essential factors affecting metabolism. In essence, your workouts will make you fat.