The Essentials of Parathyroid Hormone Venous Sampling

Imaging Recommendations for Diagnosis and Management of Primary Parathyroid Pathologies: A Comprehensive Review

Parathyroid pathologies are suspected based on the biochemical alterations and clinical manifestations, and the predominant roles of imaging in primary hyperparathyroidism are localisation of tumour within parathyroid glands, surgical planning, and to look for any ectopic parathyroid tissue in the setting of recurrent disease. This article provides a comprehensive review of embryology and anatomical variations of parathyroid glands and their clinical relevance, surgical anatomy of parathyroid glands, differentiation between multiglandular parathyroid disease, solitary adenoma, atypical parathyroid tumour, and parathyroid carcinoma. The roles, advantages and limitations of ultrasound, four-dimensional computed tomography (4DCT), radiolabelled technetium-99 (99mTc) sestamibi or dual tracer 99mTc pertechnetate and 99mTc-sestamibi with or without single photon emission computed tomography (SPECT) or SPECT/CT, dynamic enhanced magnetic resonance imaging (4DMRI), and fluoro-choline positron emission tomography (18F-FCH PET) or [11C] Methionine (11C -MET) PET in the management of parathyroid lesions have been extensively discussed in this article. The role of fluorodeoxyglucose PET (FDG-PET) has also been elucidated in this article. Management guidelines for parathyroid carcinoma proposed by the American Society of Clinical Oncology (ASCO) have also been described. An algorithm for management of parathyroid lesions has been provided at the end to serve as a quick reference guide for radiologists, clinicians and surgeons.

Cerebral venous biomarkers and veno-arterial gradients: untapped resources in Alzheimer's disease

Blood based biomarkers (BBB) derived from forearm veins for estimating brain changes is becoming ubiquitous in Alzheimer's Disease (AD) research and could soon become standard in routine clinical diagnosis. However, there are many peripheral sources of contamination through which concentrations of these metabolites can be raised or lowered after leaving the brain and entering the central venous pool. This raises the issue of potential false conclusions that could lead to erroneous diagnosis or research findings. We propose the use of simultaneous sampling of internal jugular venous and arterial blood to calculate veno-arterial gradient, which can reveal either a surplus or a deficit of metabolites exiting the brain. Methods for sampling internal jugular venous and arterial blood are described along with examples of the use of the veno-arterial gradient in non-AD brain research. Such methods in turn could help better establish the accuracy of forearm venous biomarkers.

Tricks of the trade: Techniques for preoperative localization in reoperative parathyroidectomy

BACKGROUND

Reoperative parathyroidectomy for recurrent/persistent primary hyperparathyroidism (PHPT) has high rates of failure. The goal of this study was to analyze our experience with imaging and parathyroid vein sampling (PAVS) for recurrent/persistent PHPT.

METHODS

We performed a retrospective cohort study (2002-2018) of patients with recurrent/persistent PHPT undergoing reoperative parathyroidectomy.

RESULTS

Among 181 patients, the most common imaging study was sestamibi (89.5%), followed by ultrasound (75.7%). CT had the highest rate of localization (70.8%) compared to sestamibi (58.0%) and ultrasound (47.4%). PAVS was performed in 25 patients, and localized in 96%. Ultrasound and sestamibi both demonstrated 62% PPV for operative pathology, compared to 41% in CT. PAVS was 95% sensitive with 95% PPV for predicting the correct side of abnormal parathyroid tissue.

CONCLUSIONS

We recommend a sequential imaging evaluation for reoperative parathyroidectomy, with sestamibi and/or ultrasound followed by CT. PAVS should be considered if non-invasive imaging fails to localize.

Update on Preoperative Parathyroid Localization in Primary Hyperparathyroidism

Parathyroidectomy is the treatment of choice for primary hyperparathyroidism when the clinical criteria are met. Although bilateral neck exploration is traditionally the standard method for surgery, minimally invasive parathyroidectomy (MIP), or focused parathyroidectomy, has been widely accepted with comparable curative outcomes. For successful MIP, accurate preoperative localization of parathyroid lesions is essential. However, no consensus exists on the optimal approach for localization. Currently, ultrasonography and technetium-99m-sestamibi-single photon emission computed tomography/computed tomography are widely accepted in most cases. However, exact localization cannot always be achieved, especially in cases with multiglandular disease, ectopic glands, recurrent disease, and normocalcemic primary hyperparathyroidism. Therefore, new modalities for preoperative localization have been developed and evaluated. Positron emission tomography/computed tomography and parathyroid venous sampling have demonstrated improvements in sensitivity and accuracy. Both anatomical and functional information can be obtained by combining these methods. As each approach has its advantages and disadvantages, the localization study should be deliberately chosen based on each patient's clinical profile, costs, radiation exposure, and the availability of experienced experts. In this review, we summarize various methods for the localization of hyperfunctioning parathyroid tissues in primary hyperparathyroidism.

The Current Role of Parathyroid Fine-Needle Biopsy (P-FNAB) with iPTH-Washout Concentration (iPTH-WC) in Primary Hyperparathyroidism: A Single Center Experience and Literature Review

Introduction. Primary hyperparathyroidism (PHPT) is a condition characterized by disorders of calcium–phosphate metabolism and bone metabolism caused by pathological overproduction of parathyroid hormone (PTH). The diagnosis of overt PHPT is based on the presence of clinical symptoms and laboratory abnormalities typical of this condition: hypercalcemia, hypercalciuria and elevated iPTH levels. Imaging studies are not used for diagnostic purposes; they are performed to localize the parathyroid glands prior to potential surgical treatment. Technetium 99 m sestamibi scintigraphy (Tc99 m-MIBI) is the gold standard in the assessment of pathologically altered parathyroid glands. Other diagnostic options include cervical ultrasound (US), computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET). Parathyroid biopsy (P-FNAB) with iPTH washout concentration (iPTH-WC) assessment is still an underestimated method of preoperative parathyroid gland localization. Few studies have reported the utility of US-guided P-FNAB in preoperative assessment of parathyroid lesions. The aim of the study was to present our experience with 143 P-FNAB with iPTH-WC assessment. Material and methods. Laboratory results, US findings, P-FNAB complications and comparison with other imaging techniques were described and analyzed. Results. In 133 (93.0) patients, iPTH washout-to-serum ratio exceeded threshold level 0.5 and were classified as positive results. Median iPTH-WC in this group was 16,856 pg/mL, and the iPTH-WC to serum iPTH ratio was 158. There was no correlation between iPTH-WC and serum PTH, serum calcium, parathyroid gland volume and shape index. In the group of 46 operated patients, 44 demonstrated positive iPTH-WC results, which corresponds to a sensitivity of 95.6%. In Tc99-MIBI, radiotracer retention was found in 17 cases (in 24 MIBI performed), which corresponds to a sensitivity of 52.2%. P-FNAB did not cause any major side effects −92.5% of all patients had no or mild adverse events after this procedure. Conclusions. P-FNAB with iPTH-WC is a reliable method in parathyroid adenoma localization during PHPT. Its sensitivity for diagnosis of PHPT is much higher than that of Tc99-MIBI, and in some situations, P-FNAB with iPTH-WC may even replace that method. Furthermore, cost-effectiveness of iPTH-WC is at least similar to that of Tc99-MIBI. Complications of P-FNAB are mild and we can describe this method as a safe procedure.

Evaluation of diagnostic efficacy for localization of parathyroid adenoma in patients with primary hyperparathyroidism undergoing repeat surgery

PURPOSE

Repeat surgery in patients with primary hyperparathyroidism (pHPT) is associated with an increased risk of complications and failure. This stresses the need for optimized strategies to accurately localize a parathyroid adenoma before repeat surgery is performed. However, evidence on the extent of required diagnostics for a structured approach is sparse.

METHODS

A retrospective single-center evaluation of 28 patients with an indication for surgery due to pHPT and previous thyroid or parathyroid surgery was performed. Diagnostic workup, surgical approach, and outcome in terms of complications and successful removement of parathyroid adenoma with biochemical cure were evaluated.

RESULTS

Neck ultrasound, sestamibi scintigraphy, C11-methionine PET-CT, and selective parathyroid hormone venous sampling, but not MRI imaging, effectively detected the presence of a parathyroid adenoma with high positive predictive values. Biochemical cure was revealed by normalization of calcium and parathormone levels 24-48h after surgery and was achieved in 26/28 patients (92.9%) with an overall low rate of complications. Concordant localization by at least two diagnostic modalities enabled focused surgery with success rates of 100%, whereas inconclusive localization significantly increased the rate of bilateral explorations and significantly reduced the rate of biochemical cure to 80%.

CONCLUSION

These findings suggest that two concordant diagnostic modalities are sufficient to accurately localize parathyroid adenoma before repeat surgery for pHPT. In cases of poor localization, extended diagnostic procedures are warranted to enhance surgical success rates. We suggest an algorithm for better orientation when repeat surgery is intended in patients with pHPT.

Preoperative Localization for Primary Hyperparathyroidism: A Clinical Review

With increasing use of minimally invasive parathyroidectomy (PTx) over traditional bilateral neck exploration in patients with primary hyperparathyroidism (PHPT), accurate preoperative localization has become more important to enable a successful surgical outcome. Traditional imaging techniques such as ultrasound (US) and sestamibi scintigraphy (MIBI) and newer techniques such as parathyroid four-dimension computed tomography (4D-CT), positron emission tomography (PET), and magnetic resonance imaging (MRI) are available for the clinician to detect the diseased gland(s) in the preoperative workup. Invasive parathyroid venous sampling may be useful in certain circumstances such as persistent or recurrent PHPT. We review the diagnostic performance of these imaging modalities in preoperative localization and discuss the advantages and weaknesses of these techniques. US and MIBI are established techniques commonly utilized as first-line modalities. 4D-CT has excellent diagnostic performance and is increasingly performed in first-line setting and as an adjunct to US and MIBI. PET and MRI are emerging adjunct modalities when localization has been equivocal or failed. Since no evidence-based guidelines are yet available for the optimal imaging strategy, clinicians should be familiar with the range and advancement of these techniques. Choice of imaging modality should be individualized to the patient with consideration for efficacy, expertise, and availability of such techniques in clinical practice.

Recurrent primary hyperparathyroidism: a diagnostic and management dilemma

SUMMARY

Primary hyperparathyroidism requires a surgical approach to achieve a long-term cure. However, post-surgical recurrence significantly complicates the management of this condition. A number of causes for recurrent disease are well understood and several diagnostic modalities exist to localise the culprit parathyroid adenoma although none of them is efficacious in localisation of the recurrent lesion. In this case report, we highlight a novel causative mechanism and describe a unique diagnostic sequence that enabled curative treatment to be delivered.

LEARNING POINTS

In the case described herein, we describe a novel location for a parathyroid adenoma causing recurrent PHPT. The case elucidates well the difficulties presented by such cases in terms of surgical planning and show the utility of PVS in such cases. Based on this case, we make the following recommendations: Meticulous care must be taken to prevent seeding of adenomatous tissue during primary excision. To consider the use of PVS in patients with discordant imaging in the setting of recurrent/persistent PHPT as a method to localise the causative adenoma. Same day PVS and surgery is a viable option for patients who either represent an anaesthetic risk or who are extremely anxious about the prospect of two separate procedures. Disordered calcium homeostasis is an important but forgotten cause of dysphagia which can be extremely debilitating for affected patients.

Selection of parathyroidectomy methods for primary hyperparathyroidism according to concordance between ultrasonography and MIBI scan results

Background

Determination of appropriate operative methods for primary hyperparathyroidism (PHPT) is difficult when localisation results are discordant between imaging studies. The aim of this study was to compare the efficacy of focused parathyroidectomy (FP) and bilateral neck exploration (BNE) according to the concordance in localisation results.

Method

One hundred and ninety-one patients who underwent a PHPT operation at Asan Medical Center between 2000 and 2010 were divided into two groups according to the concordance in findings between neck ultrasonography (USG) and sestamibi (MIBI) scan. Differences in clinicopathological features and surgical outcomes between the concordant (n=137) and discordant (n=54) groups were analysed.

Results

FP and BNE did not show significant differences in postoperative persistent hyperparathyroidism rates. Although intraoperative parathyroid hormone (IOPTH) monitoring was not performed in this study, the cure rates of PHPT using only USG and MIBI scans were satisfactorily high, at 98.5% in the concordant group and 96.3% in the discordant group. The cure rates of FP and Unilateral exploration in single-negative USG and MIBI scans were 100%. Multiple lesions and hyperplasia were more common in the discordant group.

Conclusions

In cases where it is difficult to apply IOPTH, FP without IOPTH is feasible in patients showing concordant or single-negative detection on USG and MIBI scans, whereas BNE is recommended in cases of discordance or double-negative results on imaging studies, to prevent recurrence or persistent disease. Appropriate selection of parathyroidectomy methods according to the concordance in USG and MIBI scans might produce good results without any difference in recurrence.

Parathyroid Imaging

Primary hyperparathyroidism (PHPT) is a common endocrine abnormality, caused in most cases by a single parathyroid adenoma. Surgery remains the first-line curative therapy in PHPT. Imaging plays a vital role in presurgical localization of parathyroid adenomas. Ultrasound provides a safe and quick imaging modality free of ionizing radiation, but is operator dependent. Sestamibi scan offers comparable sensitivity to ultrasound, improved with concurrent tomographic imaging. 4DCT remains a problem-solving technique in challenging cases and after failed neck exploration. We present an overview of various parathyroid imaging modalities, including protocols and findings, in addition to relevant pearls and pitfalls.

Selective parathyroid venous sampling in reoperative parathyroid surgery: A key localization tool when noninvasive tests are unrevealing

BACKGROUND

Preoperative localization studies are essential for parathyroid re-exploration. When noninvasive studies do not regionalize the abnormal parathyroid gland, selective parathyroid venous sampling may be employed. We studied the utility of parathyroid venous sampling in reoperative parathyroid surgery and the factors that may affect parathyroid venous sampling results.

METHODS

Patients with hyperparathyroidism and previous cervical surgery undergoing evaluation for reoperative parathyroidectomy over a 20-year period were identified. Patients with indeterminate or negative noninvasive studies underwent parathyroid venous sampling. Parathyroid hormone values were mapped with a ≥2-fold increase above peripheral signifying positive parathyroid venous sampling. These results were correlated with reoperative findings.

RESULTS

Parathyroid venous sampling was positive in 113 of 140 (81%). Re-exploration occurred in 75 (66%). Parathyroid venous sampling correctly detected the region of abnormal glands in 58 (77%). With 1 gradient, 1 abnormal gland was found in 81%. With multiple gradients, 1 abnormal gland was found in 78%, most often at the site with the largest gradient. Eighty percent of patients who underwent reoperative parathyroidectomy were biochemically cured.

CONCLUSION

Parathyroid venous sampling can guide parathyroid re-exploration when noninvasive localizing studies are indeterminate. Expectation of 1 versus multiple remaining glands was key in interpreting the results.

Evaluation of an optimal cutoff of parathyroid venous sampling gradient for localizing primary hyperparathyroidism

INTRODUCTION

Parathyroid venous sampling (PVS) has been reported to be a useful adjunctive test in localizing lesions in elusive cases of primary hyperparathyroidism (PHPT). Conventional cutoff (twofold) is now widely being used, but optimal cutoff threshold for PVS gradient based on discriminatory performance remains unclear.

MATERIALS AND METHODS

Among a total of 197 consecutive patients (mean age 58.2 years, female 74.6%) with PHPT who underwent parathyroidectomy at a tertiary center between 2012 and 2018, we retrospectively analyzed 59 subjects who underwent PVS for persistent or recurrent disease after previous parathyroidectomy, or for equivocal or negative results from conventional imaging modalities including ultrasonography (US) and Tc^99m-Sestamibi SPECT-CT (MIBI). True parathyroid lesions were confirmed by combination of surgical, pathological findings, and intraoperative parathyroid hormone (PTH) changes. Optimal PVS cutoff were determined by receiver-operating characteristics (ROC) analysis with Youden and Liu method.

RESULTS

Compared to subjects who did not require PVS, PVS group tends to have lower PTH (119.8 pg/mL vs 133.7 pg/mL, p = 0.075). A total of 79 culprit parathyroid lesions (left 40; right 39) from 59 patients (left 24; right 26; bilateral 9) were confirmed by surgery. The optimal cutoff for PVS gradient was estimated as 1.5-fold gradient (1.5 ×) with sensitivity of 61.8% and specificity of 84%. When 1.5 × cutoff was applied, PVS improved the discrimination for true parathyroid lesions substantially based on area under ROC (0.892 to 0.942, p < 0.001) when added to US and MIBI.

CONCLUSION

Our findings suggest that PVS with cutoff threshold 1.5 × can provide useful complementary information for pre-operative localization in selected cases.

Role of Venous Sampling in the Diagnosis of Endocrine Disorders

Venous sampling is the gold standard for localizing abnormal hormone secretion in several endocrine disorders. The most common indication for venous sampling is in the workup of primary aldosteronism, adrenocorticotropic hormone-dependent Cushing's syndrome, and hyperparathyroidism. In experienced hands, venous sampling is safe and accurate. This review discusses the role of venous sampling in the workup of endocrine disease, describing the underlying anatomy and pathophysiology, as an understanding of these concepts is essential for technical and clinical success.