What causes the uncontrolled excretion of water in Diabetes Insipidus?

The uncontrolled excretion of water in Diabetes Insipidus is primarily due to decreased secretion of antidiuretic hormone (ADH), also known as vasopressin. In a healthy individual, ADH is secreted by the posterior pituitary gland in response to increased plasma osmolarity or decreased blood volume, promoting water reabsorption in the kidneys.

In Diabetes Insipidus, there are generally two forms: central and nephrogenic. In central Diabetes Insipidus, there is an insufficient production of ADH due to damage to the hypothalamus or pituitary gland. This lack of ADH leads to a significant reduction in the kidneys' ability to concentrate urine, resulting in an excessive loss of water and urination of dilute urine.

In nephrogenic Diabetes Insipidus, although ADH may be produced, the kidneys do not respond appropriately to it due to receptor or aquaporin channel dysfunction. However, in both cases, the overall effect is an inability to reabsorb water effectively, leading to polyuria and resultant dehydration.

Therefore, decreased ADH secretion is the correct cause of the uncontrolled excretion of water in Diabetes Insipidus.