Maybe you should read below... when you go on a diet and reduce your calories T3 usually does drop, but TSH and T4 stays normal. Which is fine... if you can put up with feeling a little chilly.

"The researchers found reduced T3 levels -- similar to those seen in animals whose rate of aging is reduced by CR -- only in the people on CR diets. But their serum concentrations of two other hormones -- thyroxin (T4) and thyroid stimulating hormone (TSH) -- were normal, indicating that those on CR were not suffering from the thyroid disease of clinical hypothyroidism. The findings are published online in the Journal of Clinical Endocrinology and Metabolism. "
http://www.eurekalert.org/pub_relea...o-cra053106.php

and see this

Cool mice live longer
36.5 °C may be the best body temperature for fighting ageing.
http://www.nature.com/news/2006/061...1030-11_pf.html

Have such a low body temperature is a good thing, if you want to live younger for longer. Same thing has been found in humans who have lower than average body temperature.