What metabolic disturbance can occur as a side effect of HCTZ?

Hydrochlorothiazide (HCTZ) is a thiazide diuretic commonly used to treat hypertension and edema. One of the known metabolic side effects of HCTZ is hypercalcemia. This occurs because thiazides increase calcium reabsorption in the distal convoluted tubule of the kidney. As a result, HCTZ can cause elevated serum calcium levels, which is particularly important to monitor in patients with conditions that could be exacerbated by high calcium levels, such as hyperparathyroidism or certain malignancies.

While some other disturbances can occur with the use of diuretics, they do not specifically relate to the mechanism of HCTZ. For example, potassium is usually lost with thiazide diuretics, leading to hypokalemia rather than retention. Similarly, HCTZ can potentially cause hyperglycemia, but it is less commonly associated with hypoglycemia or hypernatremia directly. Hypernatremia is more related to water loss than to sodium retention, which isn't the primary action of thiazides. Thus, the association of HCTZ with hypercalcemia is a well-recognized effect and is the correct choice here.