What condition is characterized by increased thirst and frequent urination?

The condition characterized by increased thirst and frequent urination is diabetes insipidus. This disorder involves an imbalance in the body's water regulation, typically due to a deficiency of the hormone vasopressin (also known as antidiuretic hormone, ADH), which is produced by the hypothalamus and released by the posterior pituitary gland. When there is insufficient ADH, the kidneys cannot concentrate urine effectively, leading to the excretion of large volumes of dilute urine, which in turn causes increased thirst as the body seeks to compensate for the fluid loss.

In contrast, diabetes mellitus also presents with increased thirst and frequent urination, but it is primarily due to high blood sugar levels leading to osmotic diuresis. The mechanisms and hormone involvement differ significantly between the two conditions. Hypothyroidism typically does not directly cause increased thirst or urination, and adrenal insufficiency is more associated with symptoms like fatigue, weakness, and sometimes low blood pressure. Thus, diabetes insipidus is the condition that specifically highlights the role of ADH deficiency resulting in these symptoms.