A patient exhibits symptoms of primary hyperaldosteronism. Which laboratory finding would you expect?

In primary hyperaldosteronism, also known as Conn's syndrome, there is an excess production of aldosterone from the adrenal glands. This condition leads to the retention of sodium and water and increased excretion of potassium. As a result, one of the hallmark laboratory findings in this condition is hypokalemia, which indicates low levels of potassium in the blood.

The elevated aldosterone causes the kidneys to reabsorb more sodium, contributing to hypertension due to increased fluid volume. However, aldosterone also promotes the excretion of potassium, leading to a significant decrease in serum potassium levels, which is commonly seen in patients with primary hyperaldosteronism. Hypokalemia can cause numerous symptoms, including muscle weakness, cramps, and arrhythmias.

This is in contrast to other conditions that could increase renin levels or lead to hyperkalemia or metabolic acidosis. In primary hyperaldosteronism, the renin levels are usually low due to the feedback mechanism of the high sodium levels and hypertension. Therefore, the presence of hypokalemia in this patient is a key diagnostic marker for primary hyperaldosteronism.