PTH and viral infectious disease: First, it is well recognized that serum vitamin D protects against bacterial and viral infections, which may trigger diabetic ketoacidosis, and metabolic acidosis enhances urinary calcium excretion, reducing serum calcium and stimulating parathyroid hormone secretion, which expedites the conversion of 25 (OH) D3 to 1,25 (OH) 2D3 and depletes vitamin D reserves over time (22, 23).