Posted 12/20/2011 5:54 PM (GMT -6)
This is very simplistic but I understand med stuff on a simplistic level. When the thyroid's not producing enough hormone, the hormone numbers - T3 and T4 - will be below range, maybe borderline, at the border. Meanwhile, the thyroid's sending a message somewhere (hypothalamus? not sure) that it needs more hormone; the message sent is actually, get me more thyroid stimulating hormone (TSH). Hence the high TSH number.
OTOH, when the thyroid produces too much hormone, the T3 and T4 will be above range, and the TSH will be below range, maybe non existent, because it's saying, no thank you, I don't need my thyroid stimulated to produce more hormone.
It's kind of a see-saw. Occasionally the numbers won't make sense, both might be elevated, e.g. and a good endo can get to the bottom of this by monitoring carefully, checking other numbers like antibodies, etc.