It is suspected that the identity of the degradation product could be reverse T3
(3,3',5'-triiodothyronine) because this compound could be generated from T4 by a single loss of an iodine atom.
is a form of T3 that mimics T3 hormone but fails to function adequately as thyroid hormone.
Having a reverse T3 molecule to slow their metabolism and to slow the loss of whatever weight they put on during the fall harvest would have a been a huge benefit.
Two last notes on this case: First I was taught (in some forgotten conference) that food intolerances can also activate D3 and increase reverse T3 and create the illusion of hypothyroidism with normal T4 and TSH values.
Leptin resistance causes a diminished TSH secretion, a suppressed T4 to T3 conversion, an increase in reverse T3, an increase in appetite, an increase in insulin resistance, and an inhibition of lipolysis.
Reverse T3 has been shown to be a more potent inhibitor of T4 to T3 conversion than PTU (propylthiouracil), a medication used to decrease thyroid hormone levels in hyperthyroid.
Likewise, if the reverse T3 level is elevated, then it will further inhibit the conversion of T4 to T3.
A low ratio of T3 to reverse T3 is a predictor of mortality in congestive heart failure patients.
She also had borderline subclinical hypothyroidism wherein her reverse T3
was mildly elevated and her free T3 was in the barely normal range.