Which condition is characterized by excessive thirst and frequent urination?

The condition characterized by excessive thirst and frequent urination is diabetes insipidus. This disorder occurs due to a deficiency of the antidiuretic hormone (ADH), which is responsible for regulating water balance in the body by controlling the amount of water reabsorbed by the kidneys. When ADH is insufficient, the kidneys cannot reabsorb enough water, leading to the production of large volumes of dilute urine. As a result, the individual experiences increased urination (polyuria) and, consequently, excessive thirst (polydipsia) as the body attempts to compensate for the loss of fluid.

Other conditions mentioned do not primarily present with these specific symptoms. For instance, hyperglycemia, while it can lead to increased thirst and urination due to high blood sugar levels, is more specifically associated with diabetes mellitus rather than diabetes insipidus. Hyperthyroidism and hypothyroidism do have various systemic effects and can influence hydration status but do not typically manifest solely through excessive thirst and urination as seen in diabetes insipidus.