Doctors who are focusing primarily on the laboratory testing of TSH, FT4, FT3, and who are satisfied when each lab test result falls somewhere within its reference range, are failing thyroid patients.
All of this information (and a lot more besides) is in my latest book The Thyroid Patient’s Manual. See:
https://paulrobinsonthyroid.com/the-thyroid-patients-manual/
There are two important points that I need to make.
Thyroid laboratory tests do not take account of the individual needs of thyroid patients.
Thyroid lab tests all suffer from a ‘low index of individuality’. The range of variance in the population is much wider than the range of variance in the individual (this is also known as non-ergodicity). We know from research that the actual individual person ranges for levels like FT3 and FT4, are less than half as wide as the wide population ranges that doctors are using to assess our thyroid lab test results. When you make generalisations based on the population and try to apply them to the individual, you have problems. Basically, the lab reference ranges do not help much when assessing whether FT3 or FT4 is at the right level for the individual thyroid patient. We do NOT know what each thyroid patient’s actual reference range is!
This research study shows that the FT4 and FT3 reference range for each individual is less than half as wide as the population reference ranges for FT4 and FT3:
“Narrow individual variations in serum T(4) and T(3) in normal subjects: a clue to the understanding of subclinical thyroid disease.”
Stig Andersen, Klaus Michael Pedersen, Niels Henrik Bruun, Peter Laurberg
The Journal of Clinical Endocrinology & Metabolism, Volume 87, Issue 3, 1 March 2002, Pages 1068–1072.
https://doi.org/10.1210/jcem.87.3.8165
https://academic.oup.com/jcem/article/87/3/1068/2846746
Also see this blog post on the same topic:
https://paulrobinsonthyroid.com/research-shows-free-t4-and-free-t3-ranges-for-individual-thyroid-patients-are-less-than-half-as-wide-as-the-wide-population-laboratory-ranges/
The use of TSH in monitoring thyroid hormone therapy is highly unsatisfactory and should be replaced by triple FT4/FT3/TSH measurement. The presentation of symptoms of the patient should be the primary focus, above lab-test results, but supported by them. Unthinking, automatic, biochemical definition of treatment success, independent of the patient must cease. Individuality should be the decision-maker for optimum therapeutic outcomes:
“Time for a reassessment of the treatment of hypothyroidism”
John E. M. Midgley, Anthony D. Toft, Rolf Larisch, Johannes W. Dietrich & Rudolf Hoermann.
BMC Endocrine Disorders volume 19, Article number: 37 (2019)
https://bmcendocrdisord.biomedcentral.com/articles/10.1186/s12902-019-0365-4
This research article shows that the current protocols for managing thyroid hormone issues are very wrong. The way TSH is currently used is wrong, the way people are treated as if they are all the same is wrong. Simply being ‘in range’ on levothyroxine monotherapy is not going to guarantee a good outcome. We are all individuals. Many of us require either some T3 with T4 or all T3 in a few cases. We also know that we cannot be managed by simplistic measures like TSH. It is a complex article but well worth the read:
“Recent Advances in Thyroid Hormone Regulation: Toward a New Paradigm for Optimal Diagnosis and Treatment”
Hoermann, Midgley, Larisch, Dietrich.
https://www.frontiersin.org/articles/10.3389/fendo.2017.00364/full.
The top and bottom of the FT4 and FT3 thyroid laboratory tests are limiting treatment
Secondly, we also know that some laboratories include data from thyroid patients with in-range TSH levels. However, thyroid patients under treatment with T4 medication, tend to have higher FT4 and lower FT3, than non-thyroid patients.
This is because the T4-Only medication does not result in as much FT3 as a healthy person has from the conversion of T4, plus there is often a loss of T3 from the thyroid gland itself.
The net effect of this is that the bottom and the top of the reference ranges for FT4 and FT3 are influenced by the inclusion of the thyroid patient data. The top and bottom of the FT4 ranges are likely to be higher than for healthy people. The top and bottom of the FT3 ranges are likely to be lower.
As a result of this practice, you may be more likely to be considered healthy with higher inactive pro-hormone FT4 and lower biologically active FT3.
Current treatment focusing only on lab test results and lab ranges is actually failing large numbers of thyroid patients. This approach is causing many thyroid patients to remain ill.
It is currently impossible to assess what the unique individual person ranges are, other than through the treatment of a thyroid patient. In many instances, doctors are satisfied if the patient’s thyroid labs sit within the population reference ranges – virtually anywhere within them! Even though the patient may need much higher FT3 and lower FT4 (and the rT3 that comes from this) in order to feel well.
Moreover, thyroid blood tests cannot measure the FT3, FT4 and rT3 levels within the cells. They only measure the blood portion and as such are an approximation to what might be present and active within the cells. Since conversion occurs within the cells we cannot know specific information about FT3, FT4, and rT3 inside the cells. So, focusing on the clinical presentation of the patient through their symptoms and signs is critical.
The bottom line is, there is not as much value to the thyroid laboratory test results and reference ranges as is being assumed and relied upon, by most doctors and endocrinologists at the present time.
Simply having results that fit inside each lab test reference range is no guarantee of symptom relief. What is important, is finding a treatment regime that relieves symptoms, and allows the thyroid patient to live a healthy life.
The response to treatment and the changing relationships between TSH, FT4, FT3, and rT3 should be what guides dosing decisions. Sticking mechanically to the existing reference ranges without using good clinical judgement is a desperately flawed approach.
We need to have ALL the thyroid treatments available to thyroid patients, in order to ensure every individual has the right level of FT3 and FT4 for them.
The thyroid treatments using T4, T4/T3, NDT and T3-Only (when needed) all have to be available, as options from our doctors.
Current thyroid treatment is failing patients – it does not take into account research that clearly contradicts current practices.
Best wishes,
Paul
