A 38-year-old man came to the outpatient clinic presenting w…
A 38-year-old man came to the outpatient clinic presenting with fatigue, dry mouth, and passing large amounts of urine. He describes his urine as light in color and non-odorous. On further questioning, he said he had never experienced prior similar symptoms. He has always been healthy and denies prior hospitalizations. On recent routine pre-employment screening, serum electrolyte testing revealed that his serum sodium was mildly elevated. He was advised to have the test repeated in three months. When he had repeat blood work taken one week ago, there was further increase in the serum sodium level. Blood glucose level is normal. DDAVP (desmopressin) injection resulted in decrease in urine volume and increase in urine specific gravity. Based on this information, which of the following conditions is the most likely diagnosis for this patient?