Tests of thyroid hormones. A summary statement.

Last update and review: January 21, 2021.

A short summary.

Our summary statement on testing thyroid hormones.

Key points.

We recommend the following tests to assess thyroid function: TSH, total T4, free T4, total T3, free T3.

We recommend the following thyroid panel: TSH, total T4, free T4, total T3, free T3.

This panel allows to detect altered concentrations of thyroid hormones in certain life situations, for example, excessive exercise, insufficient caloric intake, excessive carbohydrate restriction, anorexia, starvation, dietary fetish, permanent caloric surplus, obesity, weight loss.

For monitoring thyroid hormone replacement therapy, reverse T3 may be useful.

The panel above is also informative if the goal is to assess thyroid hormone replacement therapy. For thyroid hormone replacement therapy, reverse T3 may also be useful, especially, for people on low carb diets or practicing caloric restriction.

Reference ranges for serum thyroid hormones and TSH. Source: Ceccarini, 2017 (1).

Discussion.

Some current guidelines recommend thyroid stimulating hormone (TSH) alone as the best test to detect and monitor thyroid dysfunction.

Kluesner et al., 2017 (2):

Current guidelines recommend thyroid stimulating hormone (TSH) alone as the best test to detect and monitor thyroid dysfunction, yet free thyroxine (FT4) and free triiodothyronine (FT3) are commonly ordered when not clinically indicated.

Ordering patterns for thyroid hormone tests can be described as uninformative or chaotic.

Kluesner et al., 2017 (2):

A record of all TFTs obtained in the San Antonio Military Health System during a 3‐ month period was extracted from the electronic medical record. The TFTs of interest were TSH, FT4, thyroid panel (TSH + FT4), FT3, total thyroxine (T4), and total triiodothyronine (T3).

Between August 1 and October 31, 2016, there were 38 214 individual TFTs ordered via 28 597 total laboratory requests; 11 486 of these requests were in patients with a history of hypothyroidism.

As you can see on the figure above from Kluesner, 2017 (2), most of the medical practitioners in the studied sample follow a questionable guidance or engage in somewhat chaotic ordering.

Altered concentrations of thyroid hormones in certain life situations: an attempt to conceptualize by Johannes W. Dietrich, Apostolos Chatzitomaris and colleagues that contains errors .

A noteworthy researcher on thyroid, Johannes W. Dietrich is signing articles and books with an ambition to provide general concepts of thyroid function regulation. Yet, some of his conceptualizatons contradict real-life observations. For example, contrary to what is depicted on the figure above by Dietrich and Chatzitomaris, endurance athletes often have high TSH and low T3, not high T3. As an exemple, we insert below a screenshot of blood tests of Ben Greenfield, a health personality, during the years when he was an elite endurance athlete.

Consulting program: Analysis of thyroid hormones in different life situations.

If you need help with ordering the right laboratory tests, interpreting results of your thyroid and other laboratory tests, do not hesitate to get in contact with us.

We can also help you to identify a competent medical practitioner in your geographic area or online.

Selected references:

1. Ceccarini G., Santini F., Vitti P. (2017) Tests of Thyroid Function. In: Vitti P., Hegedus L. (eds) Thyroid Diseases. Endocrinology. Springer, Cham.

2. Kluesner et al. J Eval Clin Pract. 2017;1–6.