Abstract
PurposeIrisin is a newly discovered adipo-myokine known for having significant effects on body metabolism. Currently, there is a discussion regarding the relation between thyroid function and irisin concentration. This study was designed to evaluate the influential role of levothyroxine replacement therapy on circulating levels of irisin in patients with recently onset hypothyroidism following total thyroidectomy.MethodsCirculating levels of thyroid hormones, irisin and other metabolic parameters, were assessed in 40 recently thyroidectomized patients (34 females, mean age 50.1 ± 15.2 years) at baseline (5–7 day after surgery) and after 2 months under replacement therapy with levothyroxine.ResultsAt baseline, circulating levels of thyroid hormones were indicative of hypothyroidism (TSH 12.7 ± 5.0 μU/mL, FT3 1.9 ± 0.7 pg/mL, FT4 8.7 ± 3.6 pg/mL). Mean serum irisin concentrations significantly increased after 2 months under replacement therapy with levothyroxine (from 2.2 ± 0.6 to 2.9 ± 0.6 μg/mL, p < 0.0001). Variations of circulating levels of irisin under levothyroxine replacement therapy were directly correlated with those of FT3 (Rho = 0.454, p = 0.0033) and FT4 (Rho = 0.451, p = 0.0035). Multivariate regression analysis revealed that changes in thyroid hormones concentrations explained up to 10% of the variations of serum irisin levels under levothyroxine replacement therapy (FT3 R2 = 0.098, FT4 R2 = 0.103).ConclusionOur study suggests that levothyroxine replacement therapy mildly influences irisin metabolism in patients with recently onset hypothyroidism following total thyroidectomy.
Highlights
Irisin, a newly discovered hormone-like adipo-myokine, is the extracellular cleaved product of fibronectin type III domain-containing 5 (FDNC5) and is regulated by peroxisome proliferator-activated receptor gamma (PPARγ) coactivator-1 alpha (PGC1α) [1]
It remains to clarify whether the effects of thyroid-axis hormones on metabolism could be possibly mediated by irisin, because the evidences from interventional human studies that would support a causal effect of thyroid axis on irisin concentrations are currently limited
This study aimed to evaluate the influential role of replacement therapy with levothyroxine (L-T4) on circulating levels of irisin in patients with recently onset hypothyroidism following total thyroidectomy
Summary
A newly discovered hormone-like adipo-myokine, is the extracellular cleaved product of fibronectin type III domain-containing 5 (FDNC5) and is regulated by peroxisome proliferator-activated receptor gamma (PPARγ) coactivator-1 alpha (PGC1α) [1]. Thyroid function could directly or indirectly be related to irisin regulation or, vice versa, irisin could affect the thyroid. In this regard, it has been proposed that increased TSH might lead to increased adipogenesis and irisin could be produced to keep the fat distribution in balance in the increased white adipose tissue [5]. Irisin has been studied in patients with thyroid dysfunction with somewhat conflicting results [5,6,7,8] It remains to clarify whether the effects of thyroid-axis hormones on metabolism could be possibly mediated by irisin, because the evidences from interventional human studies that would support a causal effect of thyroid axis on irisin concentrations are currently limited
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