Prescribing Safety Assessment (PSA) Practice Exam

Which of the following conditions is associated with hypovolaemic hyponatraemia?

1. Hydration

2. Addison's disease

3. Acidosis

4. Hyperparathyroidism

The correct answer is: Addison's disease

Hypovolaemic hyponatraemia occurs when there is a decrease in both total body sodium and total body water, leading to a low serum sodium concentration. This condition is typically associated with states of volume depletion, which can arise from various causes such as gastrointestinal losses (vomiting, diarrhea), renal losses (diuretics, adrenal insufficiency), or excessive sweating. Addison's disease specifically leads to adrenal insufficiency and a deficiency in aldosterone, which is important for sodium retention and fluid balance. In this condition, the body is unable to retain sodium, leading to loss of both sodium and water. The resultant decrease in blood volume—along with a drop in serum sodium—causes hypovolaemic hyponatraemia. In contrast, the other options do not lead to this specific condition. Hydration generally increases fluid volume and may lead to dilutional hyponatraemia rather than hypovolaemic hyponatraemia. Acidosis and hyperparathyroidism do not directly relate to volume status but involve different metabolic mechanisms and have other consequences for body biochemistry. Therefore, Addison's disease is distinctly linked to hypovolaemic hyponatraemia due to the loss of both sodium and volume.