One meta-analysis which reviewed nine studies makes the conclusion that there doesn't seem to be any clear benefit of taking a combination T3 and T4 formula (such as Armour Thyroid, Nature-Throid, or a version compounded by a pharmacy) over plain T4 formulations (such as Levothyroxine, Synthroid or similar) in persons with hypothyroidism.
This is a bit surprising because it seems to go against our normal physiology. Specifically, that (1) the body makes and uses both T3 and T4, and that (2) T3 is the more active form of thyroid hormone. In fact, the body still needs to convert the T4 made by the thyroid gland into T3 first before it is used. Critique of this conclusion includes the idea that these studies only use TSH or lab values to make a conclusion or that they use standard questionnaires for fatigue and quality of life which do not capture the total subjective experience of patients.
I would like to present two studies however, which show situations in which the addition of T3 seems to add a therapeutic benefit over using plain T4 alone.
The first study published in the New England Journal of Medicine notes that although a combination T3 and T4 formulation and a pure T4 formulation alone both improve TSH values---the combination of T3 and T4 formulation provided significantly better scores for mood improvement, neuropsychological function (such as doing better on tests for numbers and memory) and decreased depression.
The second study is more intriguing. In this study, the results show that based on objective measures alone, there doesn't seem to be much difference between taking a combination of T4 and T3 versus taking T4 alone. However, when the subjects were asked which medication they prefer---significantly more preferred the T3 and T4 combination. My interpretation is that there must be a benefit people get or feel from taking a combination of T3 and T4 that are not being "captured" by the tests and questionnaires used in this study. This benefit could be something as vague yet very important as--which medication makes me "feel most like my normal self." If this is the benefit, it is both ephemeral yet can make all the difference.
Read more about the thyroid:
Difference between different kinds of thyroid medication
Introduction to the thyroid gland, Thyroid and Iodine, Thyroid and Soy, Thyroid and Wheat Intake
2 comments:
Hi Dr Tan, I came across your post when searching for the differences between armour thyroid and porcine thyroid prepared by a compounding pharmacy - are there any reasons why you did not recommend thyroid from a compounding pharmacy?
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