To the Editor.—
The diuretic hydrochlorothiazide has been found to increase serum calcium levels and even to cause frank hypercalcemia in patients with a variety of diseases as well as in normal subjects. The mechanism for this hypercalcemic effect is not known but appears to require the presence of the parathyroid glands.The following is a report of a patient who appears to have hypercalcemia secondary to the use of the diuretic chlorthalidone (Hygroton).
Report of a Case.—
A 42-year-old woman had been treated for mild labile hypertension for three years with chlorthalidone, 25 mg every other day. She had a history of tension headaches and mild anxiety reactions. One year prior to her initial clinic visit, the patient's serum calcium level was 10.8 mg/100 ml, and ten months later, 10.6 mg/100 ml.When seen in the endocrinology clinic in December 1973 because of general fatigue and occipital headaches, she