Excess thyroid hormone, as occurs in Graves disease, is known to affect muscle. Both muscle and bone effects of thyroid hormone are frequently brought up as reasons not to prescribe T3 (liothyronine), or to reduce doses of T4 and/or T3.
This paper goes somewhat deeper and examines changes in quantities of certain substances found in the blood (metabolites) and T-cells.
I have long seen thyroid hormone testing (as in blood levels of T4 and T3) as just one factor. One that can be measured but the meaning of which is not always obvious. But we need to be aware that these levels are variable over time (within the day as well as over longer periods). And a level which is fine for one individual is not fine for another.
Looking at the impact of thyroid hormones on other substances could be a fruitful avenue. They might help reveal the actual impact of thyroid hormone on metabolism. They might lead to really simple and cheap tests - for example, if a substance accumulates in urine, a simple dip test might be feasible. Or even an electronic detection mechanism.
Further, if we know what happens to the various substances in significant hyperthyroidism, there is a possibility that they could demonstrate lack of these changes in simple low TSH situations which are due to higher does of T4 and/or T3. That is, we might be able to show whether the effects of TSH suppressive doses have the same impact as overt hyperthyroidism - or not.
Immunometabolic signatures predict recovery from thyrotoxic myopathy in patients with Graves' disease
Daiki Setoyama, Ho Yeop Lee, Ji Sun Moon, Jingwen Tian, Yea Eun Kang, Ju Hee Lee, Minho Shong, Dongchon Kang, Hyon-Seung Yi
First published: 30 December 2021
Abstract
Background
Thyroid hormone excess induces protein energy wasting, which in turn promotes muscle weakness and bone loss in patients with Graves' disease. Although most studies have confirmed a relationship between thyrotoxicosis and muscle dysfunction, few have measured changes in plasma metabolites and immune cells during the development and recovery from thyrotoxic myopathy. The aim of this study was to identify specific plasma metabolites and T-cell subsets that predict thyrotoxic myopathy recovery in patients with Graves' disease.
Methods
One hundred patients (mean age, 40.0 ± 14.2 years; 67.0% female), with newly diagnosed or relapsed Graves' disease were enrolled at the start of methimazole treatment. Handgrip strength and Five Times Sit to Stand Test performance time were measured at Weeks 0, 12, and 24. In an additional 35 patients (mean age, 38.9 ± 13.5 years; 65.7% female), plasma metabolites and immunophenotypes of peripheral blood were evaluated at Weeks 0 and 12, and the results of a short physical performance battery assessment were recorded at the same time.
Results
In both patient groups, methimazole-induced euthyroidism was associated with improved handgrip strength and lower limb muscle function at 12 weeks. Elevated plasma metabolites including acylcarnitines were restored to normal levels at Week 12 regardless of gender, body mass index, or age (P trend <0.01). Senescent CD8+CD28−CD57+ T-cell levels in peripheral blood were positively correlated with acylcarnitine levels (P < 0.05) and decreased during thyrotoxicosis recovery (P < 0.05). High levels of senescent CD8+ T cells at Week 0 were significantly associated with small increases in handgrip strength after 12 weeks of methimazole treatment (P < 0.05), but not statistically associated with Five Times Sit to Stand Test performance.
Conclusions
Restoring euthyroidism in Graves' disease patients was associated with improved skeletal muscle function and performance, while thyroid hormone-associated changes in plasma acylcarnitines levels correlated with muscle dysfunction recovery. T-cell senescence-related systemic inflammation correlated with plasma acylcarnitine levels and was also associated with small increases in handgrip strength.
Full paper freely accessible here: