Abstract: Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active. Journal Pre-proof A Randomized Pilot Study Using Calcitriol in Hospitalized Patients Yasmine M. Elamir, Hajira Amir, Steven Lim, Yesha Patel Rana, Carolina Gonzalez Lopez, Natalia Viera Feliciano, Ali Omar, William Paul Grist, Michael A. Via PII: S8756-3282(21)00341-0 DOI: https://doi.org/10.1016/j.bone.2021.116175 Reference: BON 116175 To appear in: Bone Received date: 12 June 2021 Revised date: 1 August 2021 Accepted date: 3 September 2021 Please cite this article as: Y.M. Elamir, H. Amir, S. Lim, et al., A Randomized Pilot Study Using Calcitriol in Hospitalized Patients, Bone (2021), https://doi.org/10.1016/ j.bone.2021.116175 This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2021 Published by Elsevier Inc. Journal Pre-proof COVER LETTER To Whom It May Concern, Thank you for considering our work for potential publication in the prestigious Bone Journal na lP re -p ro of Briefly: The systemic illness associated with SARS-CoV-2 infection results in hospitalization rate of 380.3 hospitalizations per 100,000 population, overwhelming health care systems. Some emerging therapies demonstrate modest benefits, but use is not feasible in large inpatient numbers. Vitamin D regulates expression of approximately 11,000 genes spanning many physiologic functions that include regulation of both innate and adaptive immune function. We investigate the potential benefit of calcitriol therapy given to patients hospitalized with COVID19. This pilot study is an open label, 1:1 randomized clinical trial of calcitriol 0.5 mcg daily for 14 days or hospital discharge vs. no treatment given to hospitalized adult patients with COVID19. We enrolled 50 consecutive patients, 25 per trial arm. The change in peripheral arterial oxygen saturation to the inspired fraction of oxygen (SaO2/FIO2 ratio) on admission and discharge between the groups the control group had an average increase of +13.2 (+/- 127.7) on discharge and the calcitriol group had an increase of +91.04 (+/- 119.08) (p= .0305), suggesting an improvement in oxygenation among subjects who received calcitriol. Additionally, 12 patients in the control group required oxygen supplementation on admission and..