Which of the following is a neurogenic cause of SIADH?

• A. Pituitary tumor
• B. Systemic infection
• C. Acute kidney injury
• D. Hypovolemia

Answer: (A)

SIADH happens when ADH is released inappropriately, causing the body to retain water, which dilutes the sodium and yields euvolemic hyponatremia with concentrated urine. When the trigger is within the central nervous system, this is a neurogenic (central) variant of SIADH. A pituitary tumor represents central nervous system involvement that can disrupt the hypothalamic–posterior pituitary axis and promote excess ADH release, making it a neurogenic cause.

Systemic infection can be associated with SIADH but is not a direct CNS-driven mechanism. Acute kidney injury reflects impaired kidney function affecting water and salt handling rather than inappropriate ADH secretion. Hypovolemia stimulates ADH as a normal compensatory response to conserve volume, which produces a pattern different from SIADH’s euvolemic hyponatremia with inappropriately high ADH.