SAT-379 Thyroid Autoimmunity and Interstitial Lung Disease - A Breathtaking Association

Abstract Disclosure: V. Moorthy: None. K. Jones: None. L.E. Kimball-Ravari: None. Background: Interstitial Lung Diseases (ILD) has a variable prognosis, and can lead to significant morbidity. Emerging evidence in literature links autoimmune thyroid disease (AITD) with ILDs. The scope of implications is not known. Case Report: We present the case of an 81-year-old female referred to Endocrinology for incidental goiter found on chest CT for evaluation of chronic dry cough. There were diffuse interstitial, slightly nodular, infiltrates throughout the lungs, more prominent in the lower lobes and a large goiter extending into the thoracic cavity. She did not have any symptoms of thyroid disease. Thyroid function labs were normal. TPO antibody titers were elevated pointing to Hashimoto’s. On ultrasound, the gland was enlarged, mildly heterogeneous with a benign appearing cystic nodule in the left lobe. The patient has no obvious risk factors for diffuse parenchymal lung disease (DPLD), including smoking, connective tissue disease (CTD), high-risk antigen exposure or potential drug-related cause. The patient was started on low-dose levothyroxine empirically for TSH suppression. Discussion: Idiopathic Nonspecific Interstitial Pneumonia is a subset of DPLD without known causes. On CT, ground glass and reticular opacities predominate the lower lung zones. Mononuclear cells infiltration and fibrosis lead to thickening of the alveolar septal walls. Depending on the signs and symptoms, current recommendations include testing for several autoimmune conditions. Autoimmune thyroid disease is overlooked. An increasing number of case reports and observational studies link AITD with DPLD. Interstitial Pneumonia with Autoimmune Features (IPAF) is a consensus category for interstitial lung diseases with features suggestive of autoimmunity that do not meet strict criteria for CTD-associated ILD. A 2022 study found that hypothyroidism is associated with increased mortality in IPAF patients, even accounting for relevant variables. The pathophysiology is likely an interplay between humoral & cytotoxic immune dysregulation, and mitochondrial dysfunction and oxidative stress. The presence of antibodies alone in a euthyroid milieu was sufficient to drive the disease process in our patient. Studying the association, its molecular basis, and therapeutic potential is an exciting direction for future research. Conclusion: AITD and hypothyroidism may be linked to ILD, warranting testing thyroid function and autoantibodies. The association is a promising venture with tremendous therapeutic potential for future thyroid research. Presentation: Saturday, July 12, 2025