Parathyroid adenoma diagnostic study of choice
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Syed Musadiq Ali M.B.B.S.[2]
Overview
Diagnostic Study of Choice
Serum calcium
- A single elevated serum calcium concentration should be repeated to confirm the presence of hypercalcemia.
- The total serum calcium concentration should be used for both the initial and the repeat serum calcium measurements.
- If a laboratory known to measure ionized calcium reliably is available, some authorities prefer to measure the ionized calcium, although this usually adds little to the diagnosis of asymptomatic primary hyperparathyroidism (PHPT) in patients with normal serum albumin concentrations and no abnormalities in acid-base balance [6].
- Ionized calcium measurements are an important adjunct to diagnosis is in patients with presumed normocalcemic PHPT.
- Ionized calcium levels should be normal. [7].
Serum PTH
- Parathyroid hormone (PTH) or PTH 1-84 assays (third-generation) should be measured concomitantly with the serum calcium level to diagnose hyperparathyroidism [8].
- PTH is increased in a higher proportion of patients with PHPT using the PTH 1-84 assay, several other studies have found no increase in diagnostic utility [10,11].
24-hour urinary calcium
- Measurement of 24-hour urinary calcium excretion is not always required for the diagnosis of PHPT.
- It is routinely measured in patients with asymptomatic PHPT in order to assess the risk of renal complications (when urine calcium is high) and thus determine subsequent management.
- Hypercalcemia and PTH that is only minimally elevated or inappropriately normal given the patient's hypercalcemia, the 24-hour urinary calcium also helps to distinguish PHPT from FHH.
- The data establishing the value of the Ca/Cr clearance ratio in differentiating FHH from PHPT are based primarily on 24-hour urine collections.
- There are insufficient data available to prove that Ca/Cr ratios calculated from spot urines are equivalent to those determined from 24-hour urines.