Abstract: Journal of Endocrinological Investigation (2021) 44:765–771 https://doi.org/10.1007/s40618-020-01370-x ORIGINAL ARTICLE Vitamin D deficiency as a predictor of poor prognosis in patients with acute respiratory failure due to COVID‑19 G. E. Carpagnano1 · V. Di Lecce1 · V. N. Quaranta2 · A. Zito3 · E. Buonamico1 G. Di Gioia1 · V. N. Valerio1 · O. Resta1 · E. Capozza1 · A. Palumbo1 · Received: 7 June 2020 / Accepted: 18 July 2020 / Published online: 9 August 2020 © The Author(s) 2020 Abstract Purpose Hypovitaminosis D is a highly spread condition correlated with increased risk of respiratory tract infections. Nowadays, the world is in the grip of the Coronavirus disease 19 (COVID 19) pandemic. In these patients, cytokine storm is associated with disease severity. In consideration of the role of vitamin D in the immune system, aim of this study was to analyse vitamin D levels in patients with acute respiratory failure due to COVID-19 and to assess any correlations with disease severity and prognosis. Methods In this retrospective, observational study, we analysed demographic, clinical and laboratory data of 42 patients with acute respiratory failure due to COVID-19, treated in Respiratory Intermediate Care Unit (RICU) of the Policlinic of Bari from March, 11 to April 30, 2020. Results Eighty one percent of patients had hypovitaminosis D. Based on vitamin D levels, the population was stratified into four groups: no hypovitaminosis D, insufficiency, moderate deficiency, and severe deficiency. No differences regarding demographic and clinical characteristics were found. A survival analysis highlighted that, after 10 days of hospitalization, severe vitamin D deficiency patients had a 50% mortality probability, while those with vitamin D ≥ 10 ng/mL had a 5% mortality risk (p = 0.019). Conclusions High prevalence of hypovitaminosis D was found in COVID-19 patients with acute respiratory failure, treated in a RICU. Patients with severe vitamin D deficiency had a significantly higher mortality risk. Severe vitamin D deficiency may be a marker of poor prognosis in these patients, suggesting that adjunctive treatment might improve disease outcomes. Keywords COVID-19 · Vitamin D deficiency · Acute respiratory failure · Mortality risk G. E. Carpagnano and V. Di Lecce contribuited equally. G. Di Gioia giusdigioia@libero.it * E. Buonamico enricobuonamico@gmail.com G. E. Carpagnano elisiana.carpagnano@uniba.it V. N. Valerio vnvale@tiscali.it V. Di Lecce valentina.dilecce89@gmail.com O. Resta onofrio.resta@uniba.it V. N. Quaranta vitalianonicola.40@gmail.com 1 Institute of Respiratory Disease, Department of Basic Medical Science, Neuroscience, and Sense Organs, University of Bari “Aldo Moro”, piazza Giulio Cesare 11, 70125 Bari, Italy E. Capozza elena.capozza@gmail.com 2 Pneumology Department, “Di Venere” Hospital Bari, Bari, Italy A. Palumbo alessandro.palumbo@policlinico.ba.it 3 Cardiology Department, “SS Annunziata” Hospital, Taranto, Italy A. Zito annapaolazito@yahoo.it 13 Vol.:(0123456789)