What symptom is characteristic of central diabetes insipidus secondary to head trauma?

• A. Decreased serum sodium concentration
• B. Excessive urine concentration
• C. Low blood pressure
• D. Excessive thirst

Answer: (D)

In central diabetes insipidus, which can occur following head trauma, the primary issue is the deficiency of antidiuretic hormone (ADH), also known as vasopressin. This hormone is produced in the hypothalamus and stored in the posterior pituitary gland. When head trauma damages the pituitary gland or hypothalamus, it leads to a decreased release of ADH.

As a result, patients will typically experience excessive thirst, known as polydipsia. This is the body's compensatory mechanism in response to excessive urine output and the resultant dehydration. Because ADH is not adequately regulating water reabsorption in the kidneys, individuals will produce large volumes of dilute urine, leading to a significant loss of water. To counteract this, they will develop an intense thirst to help restore body fluids.

Excessive urine output and increased thirst are hallmark symptoms of central diabetes insipidus, particularly when related to head trauma. Therefore, the manifestation of excessive thirst correlates directly with the underlying pathology of insufficient antidiuretic hormone due to trauma and highlights the body's response to maintain homeostasis.