How often are intrathyroidal parathyroid glands a cause of primary hyperparathyroidism, and how should they be managed?

BACKGROUND: The purpose of our study was to determine the frequency and management of intrathyroidal parathyroid glands in patients with primary hyperparathyroidism and evaluate whether intrathyroidal parathyroid glands were more often superior or inferior glands. METHODS: A retrospective review of the prospective parathyroid database was completed to determine the number of patients with primary hyperparathyroidism and an intrathyroidal parathyroid gland. Demographic data, laboratory and localization studies, operative management, pathology, and outcome were determined for patients with an intrathyroidal parathyroid gland and were compared with patients with an extrathyroidal parathyroid gland. RESULTS: From 1990-2023, 808 patients were operated on for primary hyperparathyroidism; 17 (2%) patients had an intrathyroidal parathyroid gland, an adenoma in 15 (88.2%), and a hyperplastic gland in 2 (11.8%). The mean age was 53 years; 16 (94%) patients were female. Mean calcium and parathyroid hormone was 12 mg/dL and 150 pg/mL, and there were no differences from the extrathyroidal parathyroid group. Ultrasound and Sestamibi imaging were valuable in identifying an intrathyroidal parathyroid gland in 10 of 13 patients and 13 of 17 patients, respectively. Local excision was performed in 9 (53%) patients and lobectomy in 8 (47%) patients. Intraoperative parathyroid hormone was measured and predictive of cure in 12 patients. The location of intrathyroidal parathyroid glands was determined in 15 patients and was inferior in 11 (73%). All patients were cured. No patient developed recurrent disease after a median 54-month follow-up. CONCLUSION: Intrathyroidal parathyroid glands are the cause of primary hyperparathyroidism in 2% of patients and are most often inferior glands. Local excision was accomplished in 53% of our patients.

Are 99mTC-Sestamibi Single Photon Emission Computed Tomography Scan Results Associated to the Parathyroid Cell Type in Primary Hyperparathyroidism?

INTRODUCTION: 99mTC-sestamibi scintigraphy (SPECT-CT) is a common imaging modality for parathyroid localization in primary hyperparathyroidism (PHPT). Prior studies have suggested that the cellular composition of parathyroid adenomas influences SPECT-CT imaging results. Other biochemical and anatomical factors may also play a role in false negative results. Therefore, after controlling for confounding variables, we sought to determine whether the histologic composition of parathyroid adenomas is associated to SPECT-CT results in patients with single gland disease causing PHPT. METHODS: A retrospective review of patients with PHPT due to confirmed single gland disease was performed over a 2-y period. A 1:1 propensity score matching was done between patients with positive and negative SPECT-CT results with regard to demographical, biochemical, and anatomical characteristics followed by blinded pathologic examination of cell composition in the matched pairs. RESULTS: Five hundred forty two patients underwent routine four gland exploration and 287 (53%) patients were found to have a single adenoma. Of those, 26% had a negative SPECT-CT result. There were significant differences between groups with regards to biochemical profile, gland location, and gland size. All of which became nonsignificant after propensity score matching. Adenomas were primarily composed of chief cells, with no difference between groups (95% versus 97%, P = 0.30). In the positive SPECT-CT group, chief cells were the dominant cell type in 68% of the cases, followed by mixed type (13%), oxyphil cells (12%), and clear cells (7%). This was similar to the negative SPECT-CT group (P = 0.22). CONCLUSIONS: While certain patient's clinical characteristics are associated with SPECT-CT imaging results, histologic cell type is not significantly associated.

Heterogeneous parathyroid near-infrared autofluorescence patterns are associated with single adenomas in primary hyperparathyroidism.

BACKGROUND: Primary adenoma (PA) and multi-gland hyperplasia (MGH) account for 85% and 15% of primary hyperparathyroidism (PHPT) cases, respectively. Near-infrared autofluorescence (NIRAF) enhances intraoperative parathyroid identification. We hypothesized that PA would display a more heterogeneous NIRAF pattern compared to MGH. METHODS: Patients undergoing surgery for sporadic PHPT were categorized based on the presence of PA or MGH. To quantify heterogeneity, we utilized ratios of (1) mean parathyroid gland (PG) NIRAF over background NIRAF (mean ratio), (2) minimum and (3) maximum PG NIRAF over mean PG NIRAF (minimum and maximum ratios). Additionally, a heterogeneity score was quantified using mean ratio (mean PG NIRAF over background NIRAF), and overall NIRAF (mean NIRAF of eight random 15 × 15 pixel areas). A point was assigned to ratios <0.8 or >1.2. Images were quantified by ImageJ software. Mann-Whitney test was performed for all comparisons. RESULTS: Of 78 patients, 63 had a single PA and 15 had MGH, totaling 102 PGs. There was no difference between their mean ratios. PA had a lower minimum ratio compared to that of MGH (0.86 ± 0.01 vs. 0.93 ± 0.01, p = 0.001) and a brighter maximum ratio (1.21 ± 0.02 vs. 1.12 ± 0.01, p = 0.0008). PA also scored higher on their heterogeneity scores compared to MGH (1.27 ± 0.23 vs. 0.33 ± 0.15, p = 0.001). CONCLUSION: Single parathyroid adenomas display a more heterogeneous autofluorescence pattern compared to that of multi-gland hyperplasia. Intraoperative characterization of PGs by real-time NIR imaging patterns may be a beneficial adjunct during parathyroid surgery.

Recurrent multinodular goitre and primary hyperparathyroidism due to adenoma arising in a parathyroid autotransplant more than 20 years after near-total thyroidectomy.

The patient is a female in her 60s with a remote history of a near-total thyroidectomy in 1997 for multinodular goitre. At the initial operation, she sustained a left recurrent laryngeal nerve injury. A devascularised parathyroid gland was autotransplanted into the right sternocleidomastoid muscle. She had been off of thyroid hormone for long periods, and her most recent levothyroxine requirement had fallen to only 25 mcg daily. The patient presented more than 20 years after her thyroidectomy with hoarseness, fatigue and dyspnoea. Laboratory studies suggested primary hyperparathyroidism. Imaging demonstrated bilateral pulmonary emboli and bulky thyroid tissue extending into her mediastinum. She underwent a completion thyroidectomy with the removal of a parathyroid adenoma arising in the autotransplanted parathyroid. This case illustrates the possibility of regrowth of benign thyroid tissue after thyroidectomy. In addition, to our knowledge, this is the first case report of a parathyroid adenoma arising from autotransplantation of a normal parathyroid.

Parathyroid carcinoma in a patient with primary hyperparathyroidism mimicking parathyroid adenoma.

Primary hyperparathyroidism caused by parathyroid carcinoma is extremely rare. Clinically, it is very challenging to differentiate between parathyroid carcinoma and adenoma. The correct diagnosis is made based on the histopathology of the resection specimen. This case report presents a woman in her 40s with body aches, knee joint pain, and fatigue, along with chronic kidney disease. Ultrasonography revealed a large hyperechoic lesion in the left parathyroid gland. Serum calcium, parathyroid hormone, urea, and creatinine levels were increased. The inferior parathyroid gland was surgically removed, and histopathological evaluation confirmed a diagnosis of parathyroid carcinoma. Unfortunately, many patients do not undergo complete resection due to a lack of a correct diagnosis during the initial surgery.

Evaluation of risk factors for recurrent renal stone formation among Saudi Arabian patients: Comparison with first renal stone episode.

OBJECTIVES: We evaluated the baseline characteristics, and risk factors of renal stone recurrence among Saudi Arabian patients after successful primary stone treatment. MATERIALS AND METHODS: In this cross-sectional comparative study, we reviewed the medical records of patients who presented consecutively with a first renal stone episode from 2015 to 2021 and were followed-up by mail questionnaire, telephone interviews, and/or outpatient clinic visit. We included patients who achieved stone-free status after primary treatment. Patients were divided into two groups: group I (patients with first episode renal stone) and group Ⅱ (patients who developed renal stone recurrence). The study outcomes were to compare the demographics of both groups and to evaluate the risk factors of renal stone recurrence after successful primary treatment. We used Student's t-test, Mann Whitney test or chi-square (x2) to compare variables between groups. Cox regression analyses were used to examine the predictors. RESULTS: We investigated 1260 participants (820 males and 440 females). Of this number, 877 (69.6%) didn't develop renal stone recurrence and 383 (30.4%) had recurrence. Primary treatments were percutaneous nephrolithotomy (PCNL), retrograde intrarenal surgery (RIRS), extracorporeal shock wave lithotripsy (ESWL), surgery and medical treatment in 22.5%, 34.7%, 26.5%, 10.3%, and 6%, respectively. After primary treatment, 970 (77%) and 1011 (80.2%) of patients didn't have either stone chemical analysis or metabolic work-up, respectively. Multivariate logistic regression analysis revealed that male gender (OR: 1.686; 95% CI, 1.216-2.337), hypertension (OR: 2.342; 95% CI, 1.439-3.812), primary hyperparathyroidism (OR: 2.806; 95% CI, 1.510-5.215), low fluid intake (OR: 28.398; 95% CI, 18.158-44.403) and high daily protein intake (OR: 10.058; 95% CI, 6.400-15.807) were predictors of renal stone recurrence. CONCLUSIONS: Male gender, hypertension, primary hyperparathyroidism, low fluid intake and high daily protein intake increase the risk of renal stone recurrence among Saudi Arabian patients.

Diagnostic utility of 11 C-methionine PET/CT in primary hyperparathyroidism in a UK cohort: A single-centre experience and literature review.

OBJECTIVE: Primary hyperparathyroidism is a common endocrine disorder, with 80% of all cases usually caused by one single hyperfunctioning parathyroid adenoma. Conventional imaging modalities for the diagnostic work-up of primary hyperparathyroidism (PHPT) include ultrasound of the neck, 99mTc-sestamibi scintigraphy, and four-dimensional computed tomography (4D-CT). However, the role of other imaging modalities, such as 11C-methionine PET/CT, in the care pathway for PHPT is currently unclear. Here, we report our experience of the diagnostic utility of 11C-methionine PET/CT in a single-center patient cohort (n = 45). DESIGN: Retrospective single-center cohort study. PATIENTS AND MEASUREMENTS: The data of eligible patients that underwent 11C-methionine PET/CT between 2014 and 2022 at Addenbrooke's Hospital (Cambridge, UK) were collected and analyzed. The clinical utility of imaging modalities was determined by comparing the imaging result with histopathological and biochemical outcomes following surgery. RESULTS: In patients with persistent primary hyperparathyroidism following previous surgery, 11C-methionine PET/CT identified a candidate lesion in 6 of 10 patients (60.0%), and histologically confirmed in 5 (50.0%). 11C-methionine PET/CT also correctly identified a parathyroid adenoma in 9 out of 12 patients (75.0%) that failed to be localized on other imaging modalities. 11C-methionine PET/CT had a sensitivity of 70.0% (95% CI 55.8 - 84.2%) for the detection of parathyroid adenomas. CONCLUSIONS: This study highlights a diagnostic role for 11C-methionine PET/CT in patients that have undergone unsuccessful prior surgery or have equivocal or negative prior imaging results, aiding localization and a targeted surgical approach.

Mediastinal parathyroid carcinoma: a case report and review of the literature.

BACKGROUND: Parathyroid carcinoma (PC) is an uncommon cause of primary hyperparathyroidism (PHPT) and particularly rare in the mediastinum. Herein, we present a case of mediastinal PC and conduct a related literature review. CASE PRESENTATION: We described a case of a 50-year-old female patient with PHPT due to mediastinal PC. She was initially admitted to a local hospital in her hometown with hypercalcemia and high blood concentrations of PTH (parathyroid hormone). The patient underwent neck parathyroidectomy and pathological examination suggested parathyroid adenoma. Although the overproduction of serum calcium and PTH declined after the surgery, calcium and PTH increased again one month later, so the patient was transferred to our hospital. A 99mTc-sestamibi scan revealed an ectopic finding in the mediastinum, which was also indicated on the CT image. After removing the mediastinal mass, the metabolism of calcium and PTH quickly reverted to normal and the pathologic features of the mass were consistent with PC. By reviewing the related literature, we noticed that only scattered reports were published before 1982, and those were not included in the present review due to their differences with current radiological examination and treatment methods. After excluding outdated studies, we summarized and analyzed 20 reports of isolated mediastinal PC and concluded that. Parathyroidectomy remains the only curative treatment for the disease. Furthermore, the success of treatment directly depends on accurate preoperative localization. CONCLUSION: With this study, we emphasize the importance of accurate preoperative diagnosis of mediastinal PC and improve clinicians' understanding of the disease.

Preoperative Clinical Prediction of Parathyroid Carcinoma: Two Rare Case Presentations and a Review of Literature.

BACKGROUND Parathyroid carcinoma represents about 0.005% of all malignancies and accounts for less than 1% of primary hyperparathyroidism cases. Precise preoperative diagnosis of parathyroid carcinoma is challenging, and it is usually diagnosed postoperatively by histological examination. Early suspicion of parathyroid carcinoma can lead to a more extensive surgical approach to reduce the risk of carcinoma recurrence. CASE REPORT The first case involves a 58-year-old woman who presented with severe back pain. An incidental finding on cervical magnetic resonance imaging of a soft-tissue-density mass at the right para-tracheal zone. The large size and the noticeable mass effect pushing the trachea and esophagus to the left side suggested the need for further investigations to rule out malignancy. Initially, it was thought to be a thyroid nodule investigated by fine-needle aspiration that revealed follicular thyroid cancer. After a histopathological examination, it was determined to be a parathyroid carcinoma. The second case involved a 30-year-old woman with a lower-limb tingling sensation. The significantly enlarged mass seen during thyroid ultrasound warranted surgical excision and histopathological analysis to rule out malignancy. Excision of what was considered a parathyroid adenoma revealed a histopathological finding of carcinoma, prompting a hemithyroidectomy. Both patients had high calcium and parathyroid hormone levels preoperatively. CONCLUSIONS Preoperative high calcium, intact parathyroid hormone, creatinine, and alkaline phosphatase, in addition to the lymphocyte-to-monocyte ratio and tumor diameter, are suggested to be predictive of parathyroid carcinoma diagnosis and should be carefully analyzed in all patients presenting with primary hyperparathyroidism.

[Pheochromocytoma associated with primary hyperparathyroidism and type 1 neurofibromatosis]. / Feokhromotsitoma v sochetanii s pervichnym giperparatireozom i neirofibromatozom tipa 1.

Neurofibromatosis type 1 (NF-1) is a predominantly inherited genetic disease with prevalence of 1 per 2500-3000 newborns and based on clear clinical criteria. In addition to common neurofibromas and gliomas of the visual pathways, these patients have a higher risk of various benign and malignant tumors throughout their lives including tumors of the central nervous system, membranes of peripheral nerves, gastrointestinal stromal tumors and leukemia. Endocrine diseases and neoplasms also occur in patients with NF-1 and can include extrarenal paraganglioma, primary hyperparathyroidism, gastroenteropancreatic neuroendocrine tumors, thyroid tumors and other adrenal neoplasms. We demonstrate multiple neuroendocrine neoplasia (MEN 2A) of neurofibromatosis type 1 combined with pheochromocytoma and primary hyperparathyroidism in a woman with a long history of palpitations, paroxysmal hypertension and osteoporosis. Biochemical analysis revealed severe hypercalcemia with elevated parathyroid hormone indicating primary hyperparathyroidism, as well as high fractionated normetanephrine and metanephrine in the urine as a sign of catecholamine-releasing pheochromocytoma/paraganglioma. Further scintigraphy revealed signs of solitary parathyroid adenoma causing primary hyperparathyroidism and right-sided pheochromocytoma. Clinical diagnosis of MEN-2 syndrome is based on combination of at least two major MEN-2-associated endocrine tumors. Resection of parathyroid adenoma and pheochromocytoma normalized biochemical parameters and blood pressure. Combination of pheochromocytoma with primary hyperparathyroidism and type 1 neurofibromatosis is discussed.

Surgical treatment of hyperparathyroidism with a pathologically changed parathyroid gland found in the mediastinum.

The most common indication for surgical treatment of parathyroid gland pathology is primary hyperparathyroidism where extirpation of the pathologically changed parathyroid gland is the first-choice treatment. Embryonic development of the lower pair of parathyroid glands is quite complex and is closely related to the tissue of the thymus; for this reason it is not uncommon for a parathyroid adenoma to be located in the mediastinum or directly in the tissue of the thymus. The treatment of primary hyperparathyroidism is becoming a multidisciplinary issue in which radiodiagnostics and nuclear medicine methods play a significant role as they are needed to accurately localize the affected gland and to plan an adequate surgery. In case of intrathoracic localization of parathyroid adenoma, the therapy belongs in the hands of thoracic surgery. At our department, the endocrine surgery program, including parathyroid gland surgery, has a long tradition, and complicated patients are concentrated here, often patients with refractory hyperparathyroidism after a previous procedure. In the last 10 years, almost 2,300 procedures for parathyroid pathology have been performed at the IIIrd Department of Surgery of the 1st Faculty of Medicine, Charles University and University Hospital in Motol, of which some pathologies with mediastinal localization were managed using minimally invasive methods, i.e. videothoracoscopy or robotic-assisted surgery.

The value of integration of bone scan and targeted SPECT/CT in diagnosis of primary hyperparathyroidism with multiple bone brown tumor.

Although parathyroid bone disease is rarely seen nowadays, skeletal manifestation can be the first sign of hyperparathyroidism (HPT) in some clinical practice. Nevertheless, the diagnosis of HPT is often overlooked. We describe three cases of multiple brown tumors (BT) in which bone pain and destruction were the first symptoms that masqueraded as a malignancy. However, according to the results of bone scan and targeted single-photon emission computed tomography/computed tomography (SPECT/CT), we considered BTs as the diagnosis in all of three cases. The final diagnoses were confirmed by laboratory tests and post-parathyroidectomy pathology. Parathyroid hormone (PTH) is significantly elevated in primary hyperparathyroidism (PHPT) as we know. However, such elevation is virtually never seen in malignancies. Diffuse or multiple foci of tracer uptakes in the bone scan were always seen in bone metastasis, multiple myeloma, and other bone neoplasm. When patients visited nuclear medicine for first consultation without biochemical results, radiological evidence from planar bone scan and targeted SPECT/CT can help in distinguishing the skeletal diseases. Lytic bone lesions with sclerosis, intra-focal or ectopic ossification and calcification, fluid-fluid level, and distribution of the lesions may be helpful in the differential diagnosis in these reported cases. In conclusion, when patients present with multiple foci of uptake on bone scan, targeted SPECT/CT is acquired for suspicious lesions, which can increase the diagnostic sensitivity and reduce unnecessary interventions and treatment. Moreover, BTs should be always kept in differential diagnosis of multiple lesions without a conclusive primary tumor.

Role of four-dimensional computer tomography (4D-CT) in non-localising and discordant first-line imaging in primary hyperparathyroidism.

BACKGROUND: Accurate preoperative localisation of parathyroid adenoma is imperative for the success of minimally invasive parathyroidectomy (MIP). OBJECTIVE: Our study aimed to evaluate the role of four-dimensional computer tomography (4D-CT) scan as an imaging modality in patients with failed and discordant localisation reported in the first-line imaging modalities (ultrasonography and 99mTc-MIBI-SPECT/CT). METHODS: This is a prospective cohort study performed at a university teaching centre from March 2013 to July 2021. All patients with primary hyperparathyroidism who had failed localisation by ultrasonography and 99mTc-MIBI-SPECT/CT (SpCT), or discordance between them, had 4D-CT performed in this study. RESULTS: One hundred and two sporadic cases of pHPT with failed/discordant first-line imaging had 4D-CT imaging prior to parathyroidectomy. In 102 patients, 105 parathyroid adenomas were reported on histopathology. 4D-CT was able to localise 78% of them to the correct side and 64% to the correct quadrant in 102 patients, as compared with US (correct side 21%, correct quadrant 16%) and 99mTc-MIBI-SPECT/CT (correct side 36%, correct quadrant 31%). 4D-CT had a sensitivity, precision, accuracy and F1 score for correct quadrant localisation as 79%, 81%, 66% and 80%; and for correct side localisation as 82%, 98%, 80% and 89%, respectively. 4D-CT was able to identify three ectopic adenomas (two in superior mediastinum and one in the oesophageal wall) which were not detected on US or SpCT. CONCLUSION: 4D-CT was found to be sensitive and accurate in preoperative localising of the diseased parathyroid glands after failed/discordant US and SpCT. This led to more patients being offered MIP as the primary surgery and improved operative outcomes.

Impact of Fluoro-Choline PET/CT in Reduction in Failed Parathyroid Localization in Primary Hyperparathyroidism.

INTRODUCTION: Accurate localization of the pathological parathyroid gland is a prerequisite for minimally invasive surgical management of hyperparathyroidism (HPT). Poor imaging or discordance in odd situations like ectopic adenomas, parathyroid hyperplasia, syndromic HPT results in localization dilemma thus causing failed parathyroidectomy. We studied the impact of Fluoro-Choline (FCH) PET/CT imaging in reduction in localization failure of parathyroid adenoma. MATERIALS AND METHODS: We did a retrospective observational study (2018-2021) of HPT among which 97 patients underwent focused parathyroidectomy (FP). All patients had undergone ultrasound imaging and 99mTc-sestaMIBI scan with early SPECT/CT (MIBI). When this preliminary imaging was doubtful or negative or multiple lesions were expected, FCH PET/CT was performed. We compared the localization accuracy of MIBI scan and FCH PET/CT with surgical outcomes as reference standard. RESULTS: MIBI scan showed overall lesion detection rate (LDR) of 88.65% in localization of pathological parathyroid gland in 97 patients. The addition of FCH PET/CT improved the overall lesion detection to 97.9%. The overall possible localization failure was reduced from 11.34 to 2.06% with the addition of FCH PET/CT (p < 0.05). Out of 97 patients of FP, 87 patients showed features of parathyroid adenoma. Single hyperplastic gland was seen in 7 patients, lipoadenoma was seen in 1 patient and 1 patient had features suggestive of parathyroiditis on histopathology. FCH PET/CT was a useful adjunct and showed significant reduction in localization failure of parathyroid adenoma.

An Unusual Case of Primary Hyperparathyroidism: Case Report of a Bifocal Intrathyroidal Parathyroid Carcinoma.

Intrathyroidal parathyroid carcinoma is an extremely rare cause of primary hyperparathyroidism. We reported a 51-year old woman who presented symptoms of hypercalcemia. 99mTc sestamibi single-photon emission computed tomography/computed tomography (CT) revealed a large hypermetabolic nodule in the left thyroid lobe suggestive of hyperfunctioning parathyroid tissue. 11C-methionine positron emission tomography/computed tomography (PET/CT) and 18F-fluorocholine PET/CT confirmed the nodule in the left thyroid lobe and also revealed a hypermetabolic activity on the posterior surface of the lower left pole. The patient underwent a total thyroidectomy and parathyroidectomy, and a diagnosis of bifocal intrathyroidal parathyroid carcinoma was confirmed. We present the first reported case of bifocal intrathyroidal carcinoma and discuss the discordant imaging results.

Preoperative Location Of Parathyroid Adenomas In Primary Hyperparathyroidism: The Role of Cervical Doppler Ultrasound.

INTRODUCTION: Parathyroid adenoma is the most frequent cause of primary hyperparathyroidism. In recent years, the preoperative location of parathyroid adenomas allowed minimally invasive surgical techniques that have become preferred over the traditional bilateral neck exploration. The more recent guidelines on this subject highlight the role of nuclear medicine imaging tests. The aim of this study was to review the current role of Doppler ultrasound (US) in assessing the preoperative location of parathyroid adenomas in patients with primary hyperparathyroidism. MATERIAL AND METHODS: Retrospective study based on data from patients with primary hyperparathyroidism that underwent parathyroidectomy between January 2013 and January 2022 at the Centro Hospitalar Universitário Lisboa Central. Statistical analysis was performed with IBM SPSS Statistics, version 26.0.0.0®. RESULTS: Parathyroidectomy was performed in 171 patients (77.8% females) with primary hyperparathyroidism. Cervical Doppler ultrasound was the most performed test (64.3%, n = 110) for preoperative location and detected a suspicious lesion in 98 patients (89.1%). The preoperative location of the parathyroid adenomas was assessed through the Doppler ultrasound and was compared with the surgical reports and histological findings; a correct identification was made in 76 patients (77.6%). Doppler ultrasound slightly underestimated the mean adenoma size (18.1 ± 7.7 mm preoperative versus 22 ± 8.4 mm postoperative). Calcium, parathyroid hormone levels, adenoma size and concomitant presence of thyroid nodules did not affect the accuracy of Doppler ultrasound. CONCLUSION: Doppler ultrasound showed high diagnostic accuracy even in patients with nodular thyroid disease regardless of calcium and parathyroid hormone levels and adenoma size. Furthermore, its safety, affordability and availability should favor its use as first line test in primary hyperparathyroidism to assess the preoperative location of parathyroid adenomas.