Thyroid disorders in idiopathic inflammatory myopathies: prevalence and related clinical scenarios

Background: Little is known about the relationship between thyroid diseases (TDs) and Idiopathic inflammatory myopathies (IIMs). This study aimed at evaluating the prevalence of TDs in a monocentric cohort of patients with IIMs, exploring possible correlations with clinical phenotype, organ involvement, comorbidities and quality of life (QoL). Methods: We retrospectively analysed medical records of patients with IIM according to the EULAR/ACR 2017 criteria, collecting data about demography, IIM subset, disease duration, autoantibody profile, organ involvement and comorbidities. Besides, we registered the occurrence of Hashimoto Thyroiditis (HT), Multinodular goitre (MNG), Grave’s Disease (GD) and Thyroid papillary cancer (TPC). In addition, some different patient reported outcomes were administered, to collect data on QoL. Results: A total of 191 patients were enrolled: 125 (65.4%) were female, with a mean age of 66.6 ± 13.5 years and a mean disease duration of 9.8 ± 7.4 years; 111 (58.1%) had dermatomyositis (DM), 50 (26.2%) polymyositis (PM), 11 (5.8%) clinically amyopathic DM or inclusion body myositis, 6 (3.1%) immune-mediated necrotizing myopathy and 2 (1%) juvenile DM. Ninety-nine patients (51.8%) had a TD; 53/191 (27.7%) had MNG, 42/191 (22%) had HT and 3/191 (1.6%) GD. One patient (0.5%) had a TPC. The presence of a TD was associated with oesophagus’ involvement and with a higher risk of osteoporosis and fragility fractures (p ≤ 0.01). Moreover, patients with TDs tended to accumulate a greater number of comorbidities (p < 0.001) and showed higher values of cumulative dose of glucocorticoids (p = 0.032). Finally, considering patients’ QoL, the presence of a TD was associated with lower values of the SF-36 bodily pain domain (p = 0.006). Conclusions: More than half of our IIMs patients had a TD, with a higher prevalence of both MNG and HT. Our results partially fill a lack of knowledge about the relationship between TDs and IIMs, stressing the opportunity of regularly screening patients for thyroid function. Clinical trial number: Not applicable.