Vitamin D endocrine system and COVID-19

Abstract Preclinical data strongly suggest that the vitamin D endocrine system (VDES) may have extra-skeletal effects. Cells of the immune and cardiovascular systems, and lungs can express the vitamin D receptor and overall, these cells respond in a coherent fashion when exposed to 1,25-dihydroxyvitamin D, the main metabolite of the VDES. Supplementation of vitamin D deficient subjects may decrease the risk of upper respiratory infections. The VDES also has broad anti-inflammatory and anti-thrombotic effects, and other mechanisms argue for a potential beneficial effect of a good vitamin D status on Acute Respiratory Distress Syndrome, a major complication of this SARS-2/COVID-19 infection. Activation of the VDES may thus have beneficial effects on the severity of COVID-19. Meta-analysis of observational data show that a better vitamin D status decreased the requirement of intensive care treatment or decreased mortality. A pilot study in Cordoba indicated that admission to intensive care was drastically reduced by administration of a high dose of calcifediol early after hospital admission for COVID. A large observational study in Barcelona confirmed that such therapy significantly decreased the odds ratio of mortality (OR 0.52). This was also the conclusion of a retrospective study in five hospitals of Southern Spain. A retrospective study on all Andalusian patients hospitalized because of COVID-19, based on real world data from the health care system, concluded that prescription of calcifediol (HR 0.67) or vitamin D (HR 0.75), 15?days before hospital admission decreased mortality within the first month. In conclusion, a good vitamin D status may have beneficial effects on the course of COVID-19. This needs to be confirmed by large, randomized trials but in the meantime, we recommend (rapid) correction of 25OHD deficiency in subjects exposed to this corona virus.