I was just to my dr yesterday (I just changed doctors recently) to get the results of a bunch of bloodwork that was done about 3 weeks ago. I was still feeling a lot of low-thyroid symtoms even though I had been taking Synthroid for many years. This is what he found:

1) My T4 levels & TSH levels were fine (thanx to Synthroid) but my T3 was way off. It was only yesterday that I learned (he drew me a diagram) that the T3 hormone is not measured by the TSH (which the pituitary gland excretes). TSH can only reveal if the thyroid is producing the proper levels of T4 hormone. The T3 hormone only works inside the cells (the cell takes T4, converts it into T3 for use). Synthroid only provides T4. He put me on a dose of Armour Thyroxine to take with my Synthroid in hopes of raising my T3.

2)I was iron deficient (anemic). Low iron can cause cold extremities (as well as mimic other low-thyroid symptoms). Low iron can also inhibit may body functions including the metabolizing of our thyroid hormones.

Hmmm....we'll see how this new treatment works. I get retested in Sept.