Substernal oxyphil parathyroid adenoma producing PTHrP with hypercalcemia and normal PTH level

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Abstract

Background

Parathyroid adenoma is the most common cause of primary hyperparathyroidism. Preoperative serum calcium and intact-parathyroid hormone levels are the most useful diagnostic parameters that allow differentiating primary hyperparathyroidism from non-parathyroid-dependent hypercalcemia. Parathyroidectomy is the definitive treatment for primary hyperparathyroidism. Approximately 5% of patients who underwent parathyroidectomy present with persistent or recurrent hyperparathyroidism due to ectopic localization of the adenoma. Functioning oxyphil parathyroid adenoma is an uncommon histological form, seldom causing primary hyperparathyroidism. Parathyroid adenoma with hypercalcemia exhibiting normal parathyroid hormone level is rare. An incidence of 5% to 33% has been documented in the literature; no etiologic explanation has been given. In 1987, parathyroid-hormone-related peptide was isolated as a causative factor of humeral hypercalcemia of malignancy. The presence of parathyroid-hormone-related peptide in parathyroid tissue under normal and pathological conditions has been described in the literature; however, its role in causing hyperparathyroidism has not yet been defined.

Case presentation

We present a case of persistent hypercalcemia with a normal level of intact-parathyroid hormone due to a substernal parathyroid adenoma, treated with radioguided parathyroidectomy. The final histological diagnosis was oxyphil adenoma, positive for parathyroid-hormone-related peptide antigens.

Conclusion

In clinical practice, this atypical biochemical presentation of primary hyperparathyroidism should be considered in the differential diagnosis of hypercalcemia. The parathyroid-hormone-related peptide should be considered not only in the presence of malignancy.

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Most cited references 16

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Parathyroid imaging: how good is it and how should it be done?

A Kettle, Michael O’Doherty (2006)

Hypersecretion of parathormone in primary hyperparathyroidism is common, occurring in approximately 1 in 500 women and 1 in 2,000 men per year in their fifth to seventh decades of life. This has been suggested from the literature to be primarily the result of a parathyroid adenoma (80-85% of cases), hyperplasia involving more than 1 gland, usually with all 4 glands being involved (10-15% of cases), or the result, albeit rarely, of parathyroid carcinoma (0.5-1% of cases). Surgical removal of the hypersecreting gland is the primary treatment; this procedure is best performed by a skilled surgeon who would normally find the abnormality in 95% of cases. Imaging, however, should be used to identify the site of abnormality, potentially reducing inpatient stay and improving the patient experience. Functional imaging of parathyroid tissue using thallium was introduced in the 1980s but has largely been superceded by the use of (99m)Tc-labeled isonitriles. The optimum techniques have used (99m)Tc-sestamibi with subtraction imaging or washout imaging. A recent systematic review reported the percentage sensitivity (95% confidence intervals) for sestamibi in the identification of solitary adenomas as 88.44 (87.48-89.40), multigland hyperplasia 44.46 (41.13-47.8), double adenomas 29.95 (-2.19 to 62.09), and carcinoma 33 (33). This review does not separate the washout and subtraction techniques. The subtraction technique using (99m)Tc-sestamibi and (123)I is the optimal technique enabling the site to be related to the thyroid tissue when the parathyroid gland is in the neck in a normal position. If there is an equivocal scan then confirmation with high resolution ultrasound should be used. With ectopic glands, the combined use of single-photon emission computed tomography may then provide anatomical information to enable localization of the functional abnormality. In patients who have had surgical exploration by an experienced parathyroid surgeon in a unit with an experienced nuclear medicine team and negative sestamibi imaging, it is reasonable to image the patient with (11)C methionine. It is debatable whether patients with a high likelihood of secondary hyperparathyroidism should be imaged. The only possible justification for this is to exclude an ectopic site. There is no substitute for an experienced surgeon and an experienced imaging unit to provide a parathyroid service.

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Hypercalcemia with low-normal serum intact PTH: a novel presentation of primary hyperparathyroidism.

Anthony Hollenberg, Andrew Arnold (1991)

The diagnosis of primary hyperparathyroidism has rested on the finding of hypercalcemia coupled with an elevated serum parathyroid hormone (PTH) level. Over 300 consecutive patients with primary hyperparathyroidism have had elevated or high-normal serum PTH levels using a specific immunoradiometric assay. Here we present a patient who proved to have surgically documented primary hyperparathyroidism in whom PTH levels were completely normal in all assays used. In the immunoradiometric assay, his normal result was unprecedentedly low (17 to 28 pg/mL; normal, 10 to 60 pg/mL) for this condition, and in a range consistent with non-PTH-dependent hypercalcemia or familial hypocalciuric hypercalcemia. This rare biochemical presentation of primary hyperparathyroidism should be considered in the differential diagnosis of hypercalcemia.

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Primary hyperparathyroidism with a low-normal, atypical serum parathyroid hormone as shown by discordant immunoassay curves.

J Shuck, W Lafferty, C. Hamlin … (2006)

In patients with primary hyperparathyroidism (PHP), one expects to find a serum PTH in the high or high-normal range. The presence of a low-normal PTH in PHP can be difficult to explain. Our objective was to investigate the cause of a low-normal serum PTH in a patient with PHP. A 57-yr-old asymptomatic white female from the private practice of F.W.L. presented with an 8-yr history of a rising serum calcium from 10.5-11.6 mg/dl (2.63-2.88 mmol/liter) and a low-normal serum intact PTH of 29.2 pg/ml. After localization of a parathyroid adenoma by [(18)F]fluorodesoxyglucose positron emission tomography scanning, a 120-mg parathyroid adenoma was removed with the achievement of normocalcemia for the subsequent 2 yr. Routine pre- and postoperative serum intact PTH assays were preformed at both the Quest Diagnostics regional laboratory in Pittsburgh, Pennsylvania, and at the Quest Diagnostics Nichols Institute in California. In addition, intact, biointact, and C-terminal assays were measured in undiluted, 1:2 diluted, and 1:4 diluted sera at the Nichols Institute. PTH gene sequence analysis was performed from DNA extracted both from the parathyroid adenoma and the patient's peripheral blood leukocytes. Dilution, with correction for the dilution factor, of the preoperative serum produced a progressive rise in the intact, biointact, and the C-terminal assays, whereas no dilution effect was seen in postoperative serum. No intragenic mutations in the pre-pro-PTH coding region were found in either the parathyroid adenoma or matched blood DNA samples. The discordant preoperative immunoassay curves with dilution could not be explained by the adenoma producing a mutated PTH. Furthermore, an autoantibody against the PTH produced by the adenoma is ruled out by the prompt loss of the dilution effect in the three PTH assays within 1 wk of the adenoma's excision. A posttranslational effect on the PTH molecule within the adenoma remains a possible explanation for the discordant immunoassay curves. Our report emphasizes that one cannot always rule out PHP because of a low-normal serum intact or biointact PTH. Repeated PTH measurements after serum dilution in suspected cases of PHP with low-normal PTH levels may be a useful method for detecting atypical forms of PTH.

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Author and article information

Journal

Journal ID (nlm-ta): World J Surg Oncol

Title: World Journal of Surgical Oncology

Publisher: BioMed Central

ISSN (Electronic): 1477-7819

Publication date Collection: 2008

Publication date (Electronic): 21 February 2008

Volume: 6

Page: 24

Affiliations

[1 ]Department of Applications in Surgery of Innovative Technologies, University Medical School of Bari, Italy

[2 ]Department of Pathology, University Medical School of Bari, Italy

[3 ]Department of Nuclear Medicine, University Medical School of Bari, Italy

Article

Publisher ID: 1477-7819-6-24

DOI: 10.1186/1477-7819-6-24

PMC ID: 2279131

PubMed ID: 18291038

SO-VID: 09b63552-7d81-4f4f-a3de-4c198d122d4b

License:

This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Substernal oxyphil parathyroid adenoma producing PTHrP with hypercalcemia and normal PTH level

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Abstract

Background

Case presentation

Conclusion

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25th European Students' Conference

Most cited references 16

Parathyroid imaging: how good is it and how should it be done?

Hypercalcemia with low-normal serum intact PTH: a novel presentation of primary hyperparathyroidism.

Primary hyperparathyroidism with a low-normal, atypical serum parathyroid hormone as shown by discordant immunoassay curves.

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