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Abstract

Dr Dutt and colleagues aptly call attention to the high probability of undiagnosed subclinical hypothyroidism (HT) being present among patients included in our article recently published in CHEST (September 2015)1Oldham J.M. Kumar D. Lee C. et al.Thyroid disease is prevalent and predicts survival in patients with idiopathic pulmonary fibrosis.Chest. 2015; 148: 692-700Abstract Full Text Full Text PDF PubMed Scopus (35) Google Scholar Because thyroid function tests (TFTs) were not performed for most patients with idiopathic pulmonary fibrosis (IPF), those who had subclinical HT, which is more prevalent than overt HT,2Canaris G.J. Manowitz N.R. Mayor G. Ridgway E.C. The Colorado thyroid disease prevalence study.Arch Intern Med. 2000; 160: 526-534Crossref PubMed Scopus (1934) Google Scholar may have been missed. On review of patients with IPF without known HT, for whom TFTs were available (n = 65), elevated thyroid-stimulating hormone (TSH) was observed in six. Two were subsequently diagnosed with overt HT, one with non-thyroidal illness syndrome, and three with subclinical HT, which supports the observation of these authors. Whether patients with undiagnosed subclinical HT were denied treatment with thyroid replacement therapy remains debatable, as TSH variability increases with age and treatment of a marginally elevated TSH level is of unproven benefit.3Garber J.R. Cobin R.H. Gharib H. et al.Clinical practice guidelines for hypothyroidism in adults: cosponsored by the American Association of Clinical Endocrinologists and the American Thyroid Association.Thyroid. 2012; 22: 1200-1235Crossref PubMed Scopus (577) Google Scholar The prevalence and clinical consequences of subclinical HT in patients with IPF certainly deserve further investigation because of the increased mortality risk associated with overt HT in this patient population. To facilitate such research and identify those with undiagnosed overt HT, we recommend systematic collection of TFTs in all patients with suspected IPF. These authors also noted that treatment with systemic corticosteroids, which may lead to HT through TSH suppression,4Brabant A. Brabant G. Schuermeyer T. et al.The role of glucocorticoids in the regulation of thyrotropin.Acta Endocrinol. 1989; 121: 95-100PubMed Google Scholar is often of shorter duration and less cumulative dose in patients with COPD compared to those treated with historical IPF regimens. Whereas we agree with this statement in general, we adjusted only for chronic systemic corticosteroid use in our analysis. The high percentage of chronic systemic corticosteroid use among COPD control subjects in our study likely reflects a high severity of disease, as we are a major referral center for patients with advanced obstructive lung disease. Finally, if chronic systemic corticosteroid use were a major confounder in our analysis, we would expect to see more variability in the HT OR produced by our adjusted and unadjusted logistic regression models. Idiopathic Pulmonary Fibrosis and Hypothyroidism: Cannot Forget Subclinical Disease and Difficult-to-Eliminate CorticosteroidsCHESTVol. 149Issue 2PreviewWe read with interest the original research entitled “Thyroid Disease is Prevalent and Predicts Survival in Patients With Idiopathic Pulmonary Fibrosis” in CHEST (September 2015).1 In the study, the authors compared the prevalence of hypothyroidism among patients with idiopathic pulmonary fibrosis (IPF) and control subjects with COPD. They also compared survival among patients with IPF who did or did not have hypothyroidism. In the study, the authors recorded patients as having hypothyroid only when they reported the use of thyroid replacement therapy and did not report a history of thyroidectomy or radioactive iodine ablation. Full-Text PDF