AVP and cancer: SIADH, when in isolation and in non-association in COVID-19, presents as hyponatremia due to a medical or idiopathic cause that raises antidiuretic hormone (ADH) in the body. Examples of the most common causes of SIADH include the following: central nervous system (CNS) abnormalities that affect the pituitary gland (where ADH is released), cancer (small cell lung cancer), medications (carbamazepine, selective serotonin reuptake inhibitors (SSRIs), cyclophosphamide), surgery, HIV, hormone abnormalities, viruses, and more [3].