here is a resent study on it
Dr. Barry Durrant-Peatfield on the T4/T3 Studies
I cannot let the controversy over these recent T4/T3 trials pass without placing my own thoughts on record. The last major trial pointed out that actually patients did better on T4 and T3 together than with T4 alone, which certainly supports the Drs Shames' opinion that one trial should never be regarded as final. Doctors Mitchell and Rothfeld are of much the same opinion. Even our Dr Toft has conceded the point in the last 18 months.
We all know that our patients do rather better on Armour than T4 as Dr Mercola points out; and that is because it is natural: it is the way nature does it. In nature the thyroid gland produces 80% T4 and slightly less than 20% of T3. What can possibly be wrong in supplementing a failing thyroid output in the same way? Should it not be actually the treatment of choice?
The fact that many patients do okay on T4 alone is no credit to us physicians. The body can often cope quite well, even using the actual unnatural supplementation of T4 alone. Armour thyroid works because it provides the proportion that nature in her wisdom has found works best. Clearly, the next best thing to Armour, is a combination of T4 and T3 in the correct proportion. So no physician should be reluctant to prescribe T3 as well as T4; most especially when the hypothyroidism is of long-standing, where conversion of T4 to T3 may be compromised.
I am pretty unhappy that both trials have too narrow a remit; mood and a sense of well-being simply isn't enough - there is a great deal more to hypothyroidism than this. The "anxiety" mentioned may well be that the overall dose was too high (perhaps because the combination was actually working better), or possibly (not even considered, it would seem) that there was a weakened adrenal response, which would interfere with adequate conversion or tissue uptake, so creating toxic symptoms. I am perfectly convinced that we must continue as before, listening to our patients and using commonsense.