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Master of Public Health

GlycA as a novel biomarker of systemic inflammation in hypothyroidism

AUTHORS

Galvao S , Bensenor IM , Blaha MJ , Jones S , Toth PP , Santos RD , Bittencourt M , Lotufo PA , Teixeira PFDS , . Thyroid : official journal of the American Thyroid Association. 2023 8 3; ().

ABSTRACT

BACKGROUND: GlycA is a novel glycoprotein biomarker of systemic inflammation and cardiovascu-lar risk. Our objective was to assess the levels of GlycA in individuals with hypothyroidism. We also explored if levothyroxine (LT4)-treated patients had different levels of GlycA, with attention to TSH levels.

METHODS: We performed a cross-sectional analysis, using baseline data from the ELSA-Brazil cohort study. We included only participants with serum TSH and GlycA levels measurements, using magnetic resonance spectroscopy (n=4745). We excluded individuals with endogenous hyperthyroidism and those using drugs impacting thyroid function. Participants not taking LT4 whose serum TSH was 0.4-4.0 mUI/L, were classified as euthyroid (EU) and those with elevated TSH as undiagnosed hypothyroidism (UH). For those on LT4 (n=345), adequacy of treatment was defined as TSH within the reference range. Those with TSH < 0.4 mUI/L were considered over-treated (OT), and those >4.0 mUI/L, under-treated (UT). Both (UT + OT) were considered inade-quately treated (IT). Group comparisons were performed by Kruskal-Wallis, adjusted Chi-square and the post-hoc Dunn test. Additional subgroup analysis were performed in patients with circu-lating thyroperoxidase antibodies. Respective multivariable analyses were performed to evalu-ate the relationship between thyroid-related variables and Glyc A levels (Generalized Linear Model), as well as an abnormal GlycA (> 400 µmol/L) (Logistic Binary Regression).

RESULTS: The prevalence rate of UH was 9.8% (467/4745) and, among those on LT4, only 61.7% (213/345) were AT. GlycA levels were higher in IT in comparison to EU (429 vs 410 µmol/L, p<0.01) but did not differ between UH (413 µmol/L) and EU. However, the subgroup analysis of those TPO-Ab+ showed that not only those with IT, but also UH, had higher levels of GlycA in comparison to EU (423 and 424 vs 402µmol/L, p=0.04). This association between higher levels of GlycA and IT was maintained even in multivariable analysis (odds ratio [OR] 1.53, 95% confi-dence interval [CI] 1.03, 2.31) Lower levels of GlycA were detected in AT (405 µmol/L,) com-pared to OT (432µmol/L, 0.04) and UT (423 µmol/L, p=0.02).

CONCLUSIONS: Patients with IT, both over- and under-treated, had higher GlycA levels, which may be associated with low-grade systemic inflammation and, possibly, increased cardiovascular risk.

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