The Australian study replaced 50 mcg of T4 with 10 mcg T3 -- patients took 50 mcg less T4, then took either 1) 10 mg T3 or 2) 50 mg T4 (identical capsules). They spent:
1) 10 weeks on T4 or T4/T3
2) 4 weeks on their usual T4 dose
3) Then crossed over to the opposite of whatever protocol they followed in the first 10 week period
Just as with the Bunevicius study, they used too much T3, which leads to poor T4/T3 balance. The Bunevicius study was only 5 weeks -- the longer patients take T4/T3 that is imbalanced toward T3, the more likely they are to feel poorly at the end of the study, because T4 tissue levels fall slowly when there is too much T3 in the T4/T3 prescription.
Note that they seem surprised that TSH was significantly higher on the T4/T3 -- I would have been very surprised if it had NOT been higher.
The Canadian-American study cut usual T4 doses by 50% and added T3 12.5 mcg twice daily (vs. placebo, twice daily.) Once again, the dose of T3 is ridiculously high -- at least they assessed patients at 2, 4, 6, 9 12 and 15 weeks. They maintained TSH in the "euthyroid" range by dose adjustments -- fundamentally wrong assumption that TSH is the absolute arbiter of thyroid function levels.
In short -- any T4/T3 study that does not give T4/T3 in about a 98%/2% T3 T4/T3 ratio and does not give T3 in time-release form will not come close to reproducing normal thyroid physiology.
These studies are like doing placebo injections of saline, versus 5 units MPH insulin in diabetics, finding both groups had very high blood sugars and then concluding that "insulin is no better than placebo."
Note: Dr. Blanchard is in private practice in Newton Lower Falls, Massachusetts, and can be reached at his office at 617-527-1810.