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
- The diagnosis is usually first suspected because of the incidental finding of an elevated serum calcium concentration on biochemical screening tests.
- If hypercalcemia is confirmed, intact parathyroid hormone (PTH) should be measured concomitantly with the serum calcium.
- Parathyroid adenoma is diagnosed by finding a frankly elevated PTH concentration in a patient with hypercalcemia.
- When the PTH is only minimally elevated or within the normal range, Parathyroid adenoma remains the most likely diagnosis.
- Normocalcemic hyperparathyroidism is a variant of PHPT, first recognized in 2009 by an international panel of experts.
- Patients with normocalcemic hyperparathyroidism typically come to medical attention in the setting of an evaluation for low bone mineral density (BMD), during which time PTH levels are drawn and found to be elevated in the absence of hypercalcemia.
- In order to make a diagnosis of normocalcemic hyperparathyroidism.
- In particular, all secondary causes for hyperparathyroidism, and ionized calcium levels should be normal.
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[1].
- Ionized calcium measurements are an important adjunct to diagnosis is in patients with presumed normocalcemic PHPT.
- Ionized calcium levels should be normal[2].
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.
Serum 25-hydroxyvitamin D
References
- ↑ Silverberg SJ, Bilezikian JP (June 1996). "Evaluation and management of primary hyperparathyroidism". J. Clin. Endocrinol. Metab. 81 (6): 2036–40. doi:10.1210/jcem.81.6.8964825. PMID 8964825.
- ↑ Glendenning P, Gutteridge DH, Retallack RW, Stuckey BG, Kermode DG, Kent GN (April 1998). "High prevalence of normal total calcium and intact PTH in 60 patients with proven primary hyperparathyroidism: a challenge to current diagnostic criteria". Aust N Z J Med. 28 (2): 173–8. PMID 9612524.