Do you temporarily hold diuretics when measuring 24-hour urine calcium levels in the evaluation of primary hyperparathyroidism?

It is mandatory to stop diuretics at least 2 weeks before evaluating a patient for PHPT. One should have a fasting blood sample on the morning of the end of the collection for calcium phosphate and PTH to complement the urine collection. Thiazide-type diuretics raise serum calcium and lower urine calcium, blunting two crucial parameters that define PHPT.

No. My initial evaluation for primary hyperthyroidism primarily involves looking at serum calcium in relation to other factors in its dynamic equilibrium, such as serum vitamin D and parathyroid hormone levels. I am also interested in imaging the parathyroid glands with ultrasound and CT, looking for enlargement. Although primary hyperthyroidism decreases urine calcium (that’s why we typically see hypercalcemia), I do not consider urinary electrolytes good quality diagnostic Indicators.

Stephen ...

Yes, I do when evaluating for 24-hour calcium. I also make sure to measure creatinine and sodium, and frequently will also measure for phosphorus when looking for primary hyperparathyroidism. I generally like it to be held for at least 7-10 days prior to collecting.