Optimal HCTZ Cessation for Diagnosis of Hyperparathyroidism

Overview

Primary hyperparathyroidism (PHPT) is the most common cause of hypercalcemia in the ambulatory setting. PHPT may be cured with surgery and indications for intervention have been defined and include urinary calcium/creatinine clearance. Hydrochlorothiazide (HCTZ), the most commonly prescribed medication for hypertension, reduces urinary calcium excretion and confounds urinary testing. As a result, it is universally recommended that thiazide diuretics be stopped in advance of urinary testing. To date, no studies are available to provide evidence-based guidance as to how long HCTZ must be held for urinary calcium excretion to return to steady state in PHPT. The objective of this study is to serially calculate urinary calcium/creatinine clearance ration in patients with suspected PHPT while holding HCTZ to determine the minimum duration of medication cessation necessary for urinary calcium clearance to reach steady state.

In this study, adult patients will submit serum and 24 hour urine samples prior to HCTZ cessation and at the following intervals after cessation: 4-6 days, 14-16 days, 28-30 days, adn 90-92 days. To minimize confounding variable, patients will take supplemental Vitamin D and Calcium, monitor their daily calcium intake, and monitor blood pressure weekly. Alternative, non-diuretic, antihypertensive medication(s) may be prescribed at the discretion of the enrolling provider.

Conditions