Administration of normal saline in hypovolemic hyponatremia predominantly leads to which effect on ADH?

• A. Increases ADH release
• B. No effect on ADH
• C. Increases aldosterone
• D. Suppresses ADH release

Answer: (D)

The main idea is that ADH release is controlled not only by osmolality but also by effective arterial blood volume. In hypovolemic hyponatremia, low circulating volume triggers non-osmotic ADH release via baroreceptors to conserve water. Giving normal saline increases intravascular volume, which reduces this baroreceptor-driven stimulus. As a result ADH secretion falls, collecting ducts reabsorb less water, and the kidneys excrete more free water. This is why suppressing ADH is the best answer. The other options don’t fit because isotonic saline does not boost ADH (that would worsen water retention), it does have an effect on ADH, and aldosterone is not the primary immediate response here—the volume expansion tends to reduce RAAS activity rather than increase aldosterone.