What symptom distinguishes Diabetes Insipidus (DI)?

The distinguishing symptom of Diabetes Insipidus (DI) is increased urination, particularly when it exceeds 1000 ml per day. In DI, the body has difficulty regulating water balance due to insufficient levels of the antidiuretic hormone (ADH) or the kidneys' inability to respond to ADH, leading to the excretion of large volumes of dilute urine. This symptom is a hallmark of the condition and is critical for diagnosing DI. While excessive thirst and dehydration can also be associated with DI, they are secondary responses to the polyuria (increased urination) rather than distinguishing features. In contrast to other options, which may present with overlapping symptoms, the significant volume of urine output is the primary and defining characteristic of this disorder.