Third, the normal range in this study was 0.4 to 4.0. This level, however, contradicts the latest understanding of normal thyroid levels. In early 2003, the American Association of Clinical Endocrinologists (AACE) went on the record to encourage doctors to consider treatment for patients who test outside a narrower TSH range of 0.3 to 3.0. (See Does Your Doctor Know About the New TSH Lab Standards?) The AACE announcement was based on recommendations from the National Academy of Clinical Biochemistry, part of the Academy of the American Association for Clinical Chemistry (AACC), whose new Laboratory Medicine Practice Guidelines: Laboratory Support for the Diagnosis and Monitoring of Thyroid Disease said that the upper limit of the TSH range should be reduced to 2.5 because >95% of the population with normal thyroid function have a TSH between 0.4 and 2.5, and that a TSH level betweeen 0.5 and 2.is "generally considered the therapeutic target for a standard L-T4 replacement dose for primary hypothyroidism."
Fourth, this study claims to correct for problems found in other studies, specifically, that previous studies used too much T3. However, it introduced its own new problems, as in this study, the women on the combination treatment typically had lower Free T4 levels and higher TSH levels -- two lab values that indicate worsening hypothyroidism. Certainly, it would not be expected to find measurable physiological improvements in patients who were, in some cases, made more hypothyroid. Those on the add-on combination treatment tended to be "overreplaced," meaning their TSH levels were low-normal or subclinically hyperthyroid. Again, it's not likely to find scientifically measurable improvements in patientswho have been made hyperthyroid.
The Main Problem With the Study
There is a major anomaly in the study. The study concludes that there is no demonstrable improvement when adding T3, then makes an unsupportable leap to state adding T3 to the treatment "does not offer any objective advantage over treatment with levothyroxine alone."
In reality, this study has shown two things:
1. On an "evidence-based," objective basis, there is no measurable difference between T4 plus T3 treatment, versus T4-only treatment. T4-only treatment is not better than the T4/T3 treatments.
2. For patients who are hypothyroid, the majority -- 70% -- subjectively feel better on a T3 product, even if that improvement was not documented among the limited number of specific criteria measured by researchers. And this subjective preference for the T3 combination treatments can not be attributed to placebo, because it was a "blind" study.
The researchers have no explanation for what they consider a surprising patient preference, saying: "...it is perplexing that despite the lack of objective advantages, most patients preferred combined treatment. It is possible that combined L-thyroxine–liothyronine treatment offers subtle improvements in well-being that may not be detected by the relatively insensitive methods used here to study quality of life."
With all due respect to the scientific method and "objective" data, is it truly in patients' best interests to maintain T4-only as a standard, when 70% of patients prefer T4+T3 treatment, and there are few if any specific side effects associated with low doses of T3?
The Next Steps
Ultimately, the only worthwhile conclusion to this particular study is that more research is obviously needed to determine what physiological or psychological factors ARE improved by T3, and what criteria can be measured to quantify these improvements, so scientists can have the "proof" they need to support the fact that 7 out of 10 patients prefer a combination treatment with T3.
This additional research is urgent, as until there is definitive data, far too many doctors are likely to continue limiting patients to T4-replacement, and refusing the addition of T3, refusing those patients a treatment that may in fact help them feel better.
For More Information
For more information, read Dr. John Lowe's analysis, "Thyroid Hormone Replacement Therapies: Ineffective and Harmful for Many Hypothyroid Patients" and various critiques of previous T4/T3 studies by leading thyroid experts.
Source:
Escobar-Morreale, Héctor F. MD, PhD; et. al. "Thyroid Hormone Replacement Therapy in Primary Hypothyroidism: A Randomized Trial Comparing L-Thyroxine plus Liothyronine with L-Thyroxine Alone," Annals of Internal Medicine. 15 March 2005 | Volume 142 Issue 6 | Pages 412-424 Online
