PTH and COVID-19: Different mechanisms of action have been hypothesized as responsible for the presence of hypocalcemia in patients affected by COVID-19 [20], such as calcium-dependent viral mechanisms determining intra- and extracellular cation dysmetabolism, calcium deposits in tissues, acute calcium precipitation in muscles, role of calcium in coagulation and prothrombotic state, acute malnutrition during critical illness, high levels of unsaturated and unbound fatty acids in inflammatory responses, and high prevalence of hypovitaminosis D with impaired compensatory response of parathyroid hormone.