Detection of parathyroid adenomas with multiphase 4DCT: towards a true four-dimensional technique.

BACKGROUND: Four-dimensional computed tomography (4DCT) is a commonly performed examination in the management of primary hyperparathyroidism, combining three-dimensional imaging with enhancement over time as the fourth dimension. We propose a novel technique consisting of 16 different contrast phases instead of three or four different phases. The main aim of this study was to ascertain whether this protocol allows the detection of parathyroid adenomas within dose limits. Our secondary aim was to examine the enhancement of parathyroid lesions over time. METHODS: For this prospective study, we included 15 patients with primary hyperparathyroidism and a positive ultrasound prior to surgery. We performed 4DCT with 16 different phases: an unenhanced phase followed by 11 consecutive arterial phases and 4 venous phases. Continuous axial scanning centered on the thyroid was performed over a fixed 8 cm or 16 cm coverage volume after the start of contrast administration. RESULTS: In all patients, an enlarged parathyroid lesion was demonstrated, and the mean lesion size was 13.6 mm. The mean peak arterial enhancement for parathyroid lesions was 384 Hounsfield units (HU) compared to 333 HU for the normal thyroid. No significant difference could be found. The time to peak (TTP) was significantly earlier for parathyroid adenomas than for normal thyroid tissue: 30.8 s versus 32.3 s (p value 0.008). The mean slope of increase (MSI) of the enhancement curve was significantly steeper than that of normal thyroid tissue: 29.8% versus 22.2% (p value 0.012). The mean dose length product was 890.7 mGy cm with a calculated effective dose of 6.7 mSv. CONCLUSION: Our 4DCT protocol may allow better visualization of the pattern of enhancement of parathyroid lesions, as enhancement over time curves can be drawn. In this way, wash-in and wash-out of contrast in suspected lesions can be readily demonstrated. Motion artifacts are less problematic as multiple phases are available. Exposure to our proposed 4DCT technique is comparable to that for classic helical 4DCT. Careful selection of parameters (lowering kV and SNR) can help to further reduce the dose.

miR-126-3p contributes to parathyroid tumor angiogenesis.

Tumors of the parathyroid glands are highly vascularized and display a microRNA (miRNA) profile divergent from normal parathyroid glands (PaNs). Angiogenic miRNAs, namely miR-126-3p, miR-126-5p, and miR-296-5p, have been found downregulated in parathyroid tumors. Here, we show that miR-126-3p expression levels are reduced in parathyroid adenomas (PAds; n = 12) compared with PaNs (n = 4). In situ hybridization (ISH) of miR-126-3p and miR-296-5p in 10 PAds show that miR-126-3p is expressed by endothelial cells lining the walls of great vessels and by cells within the thin stroma surrounding acinar structures. At variance, miR-296-5p was detectable in most PAd epithelial cells. Combining ISH for miR-126-3p with immunohistochemistry for the endothelial and mesenchymal markers CD34, CD31 and α-smooth muscle actin (αSMA), we could identify that miR-126-3p is localized in the αSMA-positive thin stroma. Further, miR-126-3p-expressing cells are enriched in the CD34-positive stromal cells surrounding epithelial cell acinar structures, a cellular pattern consistent with tumor-associated myofibroblasts (TAMs). In line with this, CD34-positive cells, sorted by FACS from PAds tissues, express miR-126-3p at higher levels than CD34-negative cells, suggesting that miR-126-3p downregulation promotes the endothelial-to-αSMA+ mesenchymal transition. In human mesenchymal stem cells derived from bone marrow (hBM-MSCs), a model of TAMs, the co-culture with PAds-derived cells for 5 days decreases miR-126-3p, while it increases VEGFA expression. At variance, adrenomedullin (ADM) expression is unaffected. Finally, overexpression of the miR-126-3p mimic in both hBM-MSCs and PAds-derived explants downregulates VEGFA expression levels. In conclusion, miR-126-3p is expressed by both endothelial cells and TAMs in PAds, and its downregulation promotes neoangiogenesis, possibly through VEGFA overexpression.

Angiogenesis in primary hyperparathyroidism.

Angiogenesis can be described as a formation of new vessels from the existing microvasculature and is a process of great importance to the tumor development. Parathyroid tissue can trigger spontaneous induction of angiogenesis in vitro and in vivo models in a vascular endothelial growth factor (VEGF)-dependent manner. Autotransplantated parathyroid tissue after thyroidectomy is able to form new vasculature and produce parathormone, maintaining calcium homeostasis. A great amount of factors contributes to the process of new vessel formation in primary hyperparathyroidism, such as VEGF, transforming growth factor ß, and angiopoietins. Studies demonstrated that markers for angiogenesis can be useful in distinguishing between parathyroid hyperplasia and neoplasia, due to the increased angiogenesis in parathyroid proliferative lesions compared with parathyroid adenomas. These factors include, inter alia, VEGF, VEGFR2, CD105, and fibroblast growth factor-2. Although these differences appear promising in the differential diagnosis, there is an overlap between benign and malignant parathyroid lesions and there is no definite cutoff value. Loss of heterozygosity and comparative genomic hybridization studies revealed chromosomal regions frequently altered in parathyroid tumorigenesis at 9p21, 1p21-22, 1p35-36, and 11q13. Therefore, immunohistochemistry and genetic testing should be an additional diagnostic marker in combination with the traditional criteria. A better understanding of angiogenesis in primary hyperparathyroidism could result in more precise assessment of diagnosis and more effective treatment, especially in those cases, in which the commonly used parameters are insufficient.

Tumour-associated fibroblasts contribute to neoangiogenesis in human parathyroid neoplasia.

Components of the tumour microenvironment initiate and promote cancer development. In this study, we investigated the stromal component of parathyroid neoplasia. Immunohistochemistry for alpha-smooth muscle actin (α-SMA) showed an abundant periacinar distribution of α-SMA(+) cells in normal parathyroid glands (n=3). This pattern was progressively lost in parathyroid adenomas (PAds; n=6) where α-SMA(+)cells were found to surround new microvessels, as observed in foetal parathyroid glands (n=2). Moreover, in atypical adenomas (n=5) and carcinomas (n=4), α-SMA(+) cells disappeared from the parenchyma and accumulated in the capsula and fibrous bands. At variance with normal glands, parathyroid tumours (n=37) expressed high levels of fibroblast-activation protein (FAP) transcripts, a marker of tumour-associated fibroblasts. We analysed the ability of PAd-derived cells to activate fibroblasts using human bone-marrow mesenchymal stem cells (hBM-MSCs). PAd-derived cells induced a significant increase in FAP and vascular endothelial growth factor A (VEGFA) mRNA levels in co-cultured hBM-MSCs. Furthermore, the role of the calcium-sensing receptor (CASR) and of the CXCL12/CXCR4 pathway in the PAd-induced activation of hBM-MSCs was investigated. Treatment of co-cultures of hBM-MSCs and PAd-derived cells with the CXCR4 inhibitor AMD3100 reduced the stimulated VEGFA levels, while CASR activation by the R568 agonist was ineffective. PAd-derived cells co-expressing parathyroid hormone (PTH)/CXCR4 and PTH/CXCL12 were identified by FACS, suggesting a paracrine/autocrine signalling. Finally, CXCR4 blockade by AMD3100 reduced PTH gene expression levels in PAd-derived cells. In conclusion, i) PAd-derived cells activated cells of mesenchymal origin; ii) PAd-associated fibroblasts were involved in tumuor neoangiogenesis and iii) CXCL12/CXCR4 pathway was expressed and active in PAd cells, likely contributing to parathyroid tumour neoangiogenesis and PTH synthesis modulation.

Embolization of bronchial artery-supplied ectopic parathyroid adenomas located in the aortopulmonary window.

Ectopic parathyroid adenomas in the aortopulmonary window (APW) are extremely rare, constituting only 1% of ectopic mediastinal adenomas and 0.24% of all parathyroid adenomas. The authors have encountered three patients with ectopic adenomas in the APW. In each case, the primary arterial supply to the APW adenoma arose from the bronchial artery. In addition, there was a small anastomotic arterial channel connecting the bronchial artery supplying the adenoma to the left inferior thyroid. All three adenomas were treated with transcatheter embolization, with control of hyperparathyroidism in two of three patients. One patient required thoracoscopic removal of the adenoma. It is critical that the interventionalist be aware of this arterial supply pattern to allow successful embolization of an APW ectopic adenoma.

Parathyroid incidentaloma detected during thyroid sonography - prevalence and significance beyond images.

INTRODUCTION: Parathyroid incidentaloma (PTI) designates a nodule discovered incidentally during thyroid sonography, and whose location and aspect suggests an abnormal parathyroid. Our aim was to assess the prevalence of PTI, their functional characteristics and to identify the factors correlated with their presence. PATIENTS AND METHODS: We recorded all patients detected with PTI between January 2009 and December 2011, in our department. Serum calcium, parathyroid hormone (PTH), thyroid stimulating hormone (TSH), free thyroine (FT4) and anti thyroid peroxidase antibodies (anti-TPO Ab) were measured. RESULTS: From a total of 2662 thyroid ultrasounds, 32 patients were identified with PTI (prevalence 1.2%). The diagnosis of a functional parathyroid adenoma was confirmed in 12 patients (37.5%). There was no significant difference in size, location, echogenicity or vascular pattern between the functioning adenomas and the other PTI. The only parameter correlated with the non functioning lesion was the multinodular pattern of the thyroid (multinodular goiter or macronodular autoimmune thyroiditis). CONCLUSIONS: Although rare, the ultrasound identification of an image suggestive for a pathological parathyroid gland requires the evaluation of the functioning character of the lesion, more than one third PTI being hyperfunctional. The concomitance of a nodular goiter decreases the probability of a primary hyperparathyroidism.

Treatment of medically refractory hypercalcemic crisis.

INTRODUCTION: A 58-year-old patient was admitted to the intensive care unit for severe hypercalcemia (total Ca 5.30 mmol/L) complicated with status epilepticus, hypertensive crisis and acute renal failure. Renal replacement therapy was explored as a method for treating medically refractory hypercalcemia. METHODS: Because of hemodynamic instability during intermittent hemodialysis (IHD), continuous venovenous hemofiltration (CVVH) with high rates of calcium-free replacement fluids was instituted. Epoprostenol rather than citrate was used as anticoagulation to ensure adequate extracorporeal anticoagulation. RESULTS: CVVH was continued for 40 hours total during which ionized calcium decreased from 2.19 to 1.07 mmol/L. The etiology of the hypercalcemia was from autoinfarction of a parathyroid adenoma. CONCLUSIONS: This is the first case of hypercalcemia treated with CVVH with epoprostenol anticoagulation. This method avoids some of the pitfalls of using intermittent hemodialysis. It is also a rare example of hypercalcemia induced posterior reversible encephalopathy syndrome (PRES).

Evaluation of the microvascularization of pathologic parathyroid glands in patients with primary hyperparathyroidism using conventional ultrasound and contrast-enhanced ultrasound.

PURPOSE: The objective was to characterize the microcirculation of parathyroid adenomas using contrast-enhanced ultrasound (CEUS) and to evaluate if it can be used for diagnosis and localization of pathologic glands. PATIENTS AND METHODS: Thirty patients with primary hyperparathyroidism scheduled for parathyroidectomy were enrolled. Preoperatively, all patients underwent B-Scan sonography, Colour coded Doppler Sonography (CCDS), Power Doppler (PD) and CEUS. The diagnostic confidence concerning B-Scan, CCDS, PD and CEUS was classified into six grades (0: no adenoma; 5: adenoma). RESULTS: Using CEUS, all adenomatous glands showed a typical dynamic microvascularization. B-Scan showed a mean grade of 2.18, CCDS 2.29, PD 2.33, CEUS 4.29 (6-9 MHz transducer) and 3.52 (6-15 MHz). The differences between CEUS and conventional sonography were all statistically significant (p < 0.05). CEUS noted a sensitivity of 98.4% and specificity of 98.4% for the detection of adenomatous glands. CONCLUSION: CEUS facilitates the detection and diagnosis of pathologic parathyroid glands due to their typical microvascularization.

Contrast-enhanced ultrasonography (CEUS) using early dynamic in microcirculation for localization of pathological parathyroid glands: first-line or complimentary diagnostic modality?

BACKGROUND: Contrast-enhanced ultrasonography (CEUS) represents a new diagnostic tool to localize pathological parathyroid glands. The aim of this study was to differentiate the capability of CEUS as first-line or complimentary modality for the detection of hyperfunctioning parathyroid glands. METHODS: Sixty patients with pHPT were admitted to the University Hospital Regensburg between 8/2009 and 3/2011. Conventional and contrast-enhanced ultrasonography (CEUS) using a linear probe (6-9 MHz, LOGIQ E9/GE) was performed in all patients preoperatively. The sensitivity of CEUS was analyzed to determine its potential as first line or complimentary diagnostic procedure. RESULTS: Using CEUS 98.3% of all pathological glands could be detected in the correct quadrant whereas conventional ultrasonography (70%) (p < 0.001) revealed less sensitivity. In all patients CEUS indicated a correct side localization of the hyperfunctioning parathyroid gland. The advantage of CEUS was the detection of the early dynamic on the capillary level immediately after contrast injection. Overall, CEUS permit minimally invasive video-assisted parathyroidectomy in 45 patients. 15 patients required conventional procedure due to concomitant goiter. All patients showed normal calcium and parathyroid hormone serum levels three months after surgery. CONCLUSIONS: CEUS represents a highly sensitive diagnostic modality for localization of pathologic parathyroid glands in patients with pHPT. Nevertheless, it can only be recommended as first-line diagnostic procedure in specialized clinical centers with experienced investigators.

Expression of parathyroid-specific genes in vascular endothelial progenitors of normal and tumoral parathyroid glands.

Parathyroid tissue is able to spontaneously induce angiogenesis, proliferate, and secrete parathyroid hormone when autotransplanted in patients undergoing total parathyroidectomy. Angiogenesis is also involved in parathyroid tumorigenesis. Here we investigated the anatomical and molecular relationship between endothelial and parathyroid cells within human parathyroid glands. Immunohistochemistry for CD34 antigen identified two subpopulations in normal and tumoral parathyroid glands: one constituted by cells lining small vessels that displayed endothelial antigens (factor VIII, isolectin, laminin, CD146) and the other constituted of single cells scattered throughout the parenchyma that did not express endothelial markers. These parathyroid-derived CD34(+) cells were negative for the hematopoietic and mesenchymal markers CD45, Thy-1/CD90, CD105, and CD117/c-kit; however, a subset of CD34(+) cells co-expressed the parathyroid specific genes glial cell missing B, parathyroid hormone, and calcium sensing receptor. When cultured, these cells released significant amount of parathyroid hormone. Parathyroid-derived CD34(+) cells, but not CD34(-) cells, proliferated slowly and differentiated into mature endothelial cells. CD34(+) cells from parathyroid tumors differed from those derived from normal parathyroid glands as: 1) they were more abundant and mainly scattered throughout the parenchyma; 2) they rarely co-expressed CD146; and 3) a fraction co-expressed nestin. In conclusion, we identified cells expressing endothelial and parathyroid markers in human adult parathyroid glands. These parathyroid/endothelial cells were more abundant and less committed in parathyroid tumors compared with normal glands, showing features of endothelial progenitors, which suggests that they might be involved in parathyroid tumorigenesis.

Ultrasound usage in the head and neck surgeon's office.

PURPOSE OF REVIEW: To review the essential developments in neck sonography published in the past 12 months and to elucidate their influence on the indications and diagnostic accuracy of office-based ultrasonography. RECENT FINDINGS: In the screening of the neck in patients with squamous cell carcinoma, sonographic and duplex sonographic characteristics have been described to identify lymph node metastases, that is, size, shape, echogenicity, homogeneity, absence of hilar sign and hilar vessel, surface irregularity, necrotic areas, evidence of extracapsular spread, peripheral perfusion pattern, focal vascularization defects, and high pulsatility index. The combination of conventional ultrasound, duplex sonography, and ultrasound-guided fine-needle aspiration biopsies (USgFNAB) achieves an overall accuracy of nearly 100%. Ultrasound has been found to be most accurate in the diagnosis and differential diagnosis of thyroid and parathyroid disorders, the localization of parathyroid adenomas and the differential diagnosis of thyroid gland disorder. Sonographic characteristics, however, are mostly unspecific. Sonography provides the chance to obtain cytologic material under direct view by USgFNAB. SUMMARY: Office-based ultrasonography is a simple and rewarding technique that is enhanced by the experience of the investigator. The neck surgeon who is caring for the patient might use this information for diagnostic and therapeutic management. Due to high accuracy, noninvasiveness, and lack of radiation exposure, ultrasonography is required in the diagnosis and differential diagnosis of any pathologic masses in the entire neck and prior to any surgical procedure. Future developments, that is, elastography, might lead to further improvement in the diagnostic accuracy to differentiate benign and malignant masses.

Microvessel density in human normal and neoplastic parathyroids.

Objective. Information on angiogenesis in parathyroid pathology is scanty and in particular no data are available in parathyroid carcinomas. The aim of this study was to analyze angiogenesis as microvascular density (MVD) in parathyroid neoplastic progression from normal gland to adenoma and carcinoma. Methods. Sections from formalin-fixed, paraffin-embedded specimens of 33 normal parathyroids, 43 sporadic parathyroid adenomas, and 6 parathyroid carcinomas were cut for immunohistochemistry using anti-endothelial marker CD34. MVD was evaluated in each specimen as number microvessels per mm2. MVD data were compared with some anatomoclinical parameters as tumor size, serum calcium, and parathyroid hormone (PTH) level. Results. All normal parathyroid glands, all carcinomas, and 8 adenomas out of 43 (18%) showed MVD less than 100 microvessels/mm2 (median 70.8; 95%CI 66.9-88.5); in the majority of parathyroid adenomas (n = 35; 82%) the number of microvessels/mm2 was higher than 100 (median 188.3; 95%CI 174.9-210.1). In adenomas both preoperative serum intact PTH concentration and the diameters were significantly and inversely related to the microvessel density (r = 0.320, p < 0.05 and r = 0.334, p < 0.05, respectively). Conclusions. This study shows that in parathyroid adenomas MVD is heterogeneous and negatively related to the endocrine activity (secretory status and tumor size). Therefore, angiogenesis in parathyroid adenomas and carcinomas appears to be an early event, which does not follow a parallel increase in size.

Expression of nitric oxide synthases in parathyroid gland adenoma and parathyroid gland hyperplasia.

OBJECTIVE: The aim of the presented study was to perform the immunohistochemical detection of endothelial (eNOS) and inducible (iNOS) isoform of nitric oxide synthase in the adenomatous and hyperplastic parathyroid gland in relation to the apoptotic process. DESIGN AND SETTING: Tissue samples from 12 patients with parathyroid gland adenoma (PGA) and 10 patients with secondary parathyroid gland hyperplasia (PGH) were collected during surgery at the Department of Otorhinolaryngology and Head and Neck Surgery of The First Faculty of Medicine in Prague. METHODS: Three-step immunoperoxidase reaction on acetone-fixed cryostat sections was performed using both polyclonal and monoclonal antibodies against eNOS and iNOS. The detection of apoptotic cells was done using antibody against cleaved caspase-3 as an apoptotic marker. RESULTS: The immunoreactivity to eNOS antibody was observed in the endothelial lining of vessels in PGA, PGH and in the rim of normal parathyroid gland adjacent to PGA sample. Variable expression of eNOS was confirmed in arteries, arterioles, capillaries and veins in the glandular parenchyma as well as in the surrounding connective tissue. There was no iNOS immunoreactive cell detected in any examined sample. No apoptotic cells were detected. MAIN RESULT: Our findings confirm that eNOS is regularly expressed in the vasculature of PGA and PGH. CONCLUSION: eNOS observed in the vasculature of the enlarged parathyroid glands can serve as a factor that contributes to the viability of hypertrophic pathologic tissue. The lack of stimulating signals may be a reason for negative iNOS detection and negligible apoptotic rate.

Spontaneous short-term remission of primary hyperparathyroidism from infarction of a parathyroid adenoma.

We report a 39-yr-old woman with spontaneous short-term remission of primary hyperparathyroidism (PHPT). She was referred to our Department for PHPT with bilateral kidney stones diagnosed elsewhere; at the time of our observation she had developed anterior neck pain associated with swelling and tenderness. Biochemical data (serum ionized calcium and PTH) suggested a remission of the PHPT. The local symptoms gradually improved and disappeared over the next several days without therapy. Serum ionized calcium and PTH levels remained normal for up to 11 months. Subsequently, the patient had a recurrence of PHPT with mild hypercalcemia and elevated PTH levels. The patient underwent surgery and pathological examination revealing a 1.0 x 1.2 cm parathyroid adenoma with areas of necrosis with hemosiderinladen macrophages. In conclusion, we describe a case of spontaneous short-term remission of PHPT due to infarction of parathyroid adenoma.

Angiogenesis in endocrine tumors.

Angiogenesis is the process of new blood vessel development from preexisting vasculature. Although vascular endothelium is usually quiescent in the adult, active angiogenesis has been shown to be an important process for new vessel formation, tumor growth, progression, and spread. The angiogenic phenotype depends on the balance of proangiogenic growth factors such as vascular endothelial growth factor (VEGF) and inhibitors, as well as interactions with the extracellular matrix, allowing for endothelial migration. Endocrine glands are typically vascular organs, and their blood supply is essential for normal function and tight control of hormone feedback loops. In addition to metabolic factors such as hypoxia, the process of angiogenesis is also regulated by hormonal changes such as increased estrogen, IGF-I, and TSH levels. By measuring microvascular density, differences in angiogenesis have been related to differences in tumor behavior, and similar techniques have been applied to both benign and malignant endocrine tumors with the aim of identification of tumors that subsequently behave in an aggressive fashion. In contrast to other tumor types, pituitary tumors are less vascular than normal pituitary tissue, although the mechanism for this observation is not known. A relationship between angiogenesis and tumor size, tumor invasiveness, and aggressiveness has been shown in some pituitary tumor types, but not in others. There are few reports on the role of microvascular density or angiogenic factors in adrenal tumors. The mechanism of the vascular tumors, which include adrenomedullary tumors, found in patients with Von Hippel Lindau disease has been well characterized, and clinical trials of antiangiogenic therapy are currently being performed in patients with Von Hippel Lindau disease. Thyroid tumors are more vascular than normal thyroid tissue, and there is a clear correlation between increased VEGF expression and more aggressive thyroid tumor behavior and metastasis. Although parathyroid tissue induces angiogenesis when autotransplanted and PTH regulates both VEGF and MMP expression, there are few studies of angiogenesis and angiogenic factors in parathyroid tumors. An understanding of the balance of angiogenesis in these vascular tumors and mechanisms of vascular control may assist in therapeutic decisions and allow appropriately targeted treatment.

Parathyroid adenoma autoinfarction: a report of a case.

BACKGROUND: Parathyroid adenoma autoinfarction, although uncommon, is an entity that has been previously reported in the literature; however, the influence of intraoperative parathyroid hormone (PTH) monitoring on therapeutic management has not been reported. METHODS: We present a case of parathyroid autoinfarction that is unique in that it applies a new technology to parathyroid surgery: intraoperative PTH monitoring. RESULTS: Intraoperative PTH monitoring aided in the successful surgical management of this patient. CONCLUSIONS: Intraoperative PTH monitoring can serve as a therapeutic adjunct in the surgical management of parathyroid adenoma autoinfarction.

Sonography in primary hyperparathyroidism: review with emphasis on scanning technique.

OBJECTIVE: To review the sonographic features and focused sonographic scanning techniques that may assist in the preoperative localization of parathyroid adenomas in patients with primary hyperparathyroidism. METHODS: The sonographic findings were reviewed in 54 of 58 consecutive patients with pathologically proven parathyroid adenomas. A systematic scanning approach including real-time gray scale, color and power Doppler, and graded compression gray scale imaging was used in all patients. RESULTS: Fifty-four (93%) of 58 proven adenomas were correctly identified by sonography. Gray scale imaging alone was sufficient for identifying 26 (100%) of 26 large (> or =1-cm) and 3 (11%) of 25 small (<1-cm) parathyroid adenomas. However, for 25 (89%) of 28 small adenomas, a combination of color and power Doppler and graded compression real-time gray scale imaging was required for sonographic localization and identification. CONCLUSIONS: Knowledge of typical locations and characteristic imaging features, as well as a systematic scanning approach, can result in accurate preoperative sonographic localization of parathyroid adenomas.

Spontaneous infarction of a parathyroid adenoma: two case reports and review of the literature.

The spontaneous infarction of a parathyroid adenoma is an uncommon event, although it has been previously described. Patients may present symptomatically or experience resolution of their hyperparathyroidism. As such the appropriate clinical management of these patients remains unclear. We present two cases of spontaneous infarction of parathyroid adenomas. The first presented with neck pain and dysphagia and experienced at least temporary resolution of her hyperparathyroidism. The second patient experienced a fall in his parathyroid hormone and calcium levels before neck exploration. Infarcted parathyroid adenoma was diagnosed on pathologic evaluation of the surgical specimen. Inflammation surrounding the infarcted adenoma provided for a technically difficult operation. Although resolution of hyperparathyroidism has been described postinfarction, a regeneration of the parathyroid adenoma may occur. Therefore neck exploration and parathyroidectomy should still be considered. We propose a period of observation after diagnosis of spontaneous parathyroid adenoma infarction to avoid these acute inflammatory changes that have been described.