What is the primary cause of diabetes insipidus?

The primary cause of diabetes insipidus is a deficiency of antidiuretic hormone (ADH), also known as vasopressin. ADH is a hormone produced by the hypothalamus and stored in the posterior pituitary gland. Its main role is to regulate water balance in the body by promoting water reabsorption in the kidneys. When there is a deficiency of ADH, the kidneys cannot reabsorb enough water, leading to the excretion of large volumes of dilute urine. This condition can result in increased thirst (polydipsia) as the body attempts to compensate for the fluid loss.

Other options such as excess insulin production, an overactive thyroid, and insulin resistance pertain to different endocrine disorders and do not relate to the mechanisms or causes of diabetes insipidus. Understanding the role of ADH is key in recognizing how its deficiency leads to the symptoms associated with this condition.