Comparison of parathyroid hormone levels from the intact and whole parathyroid hormone assays after parathyroidectomy for primary and secondary hyperparathyroidism

Intraoperative parathyroid hormone measurement pitfalls: parathyroid hormone spikes with carboxyl-terminal parathyroid hormone fragments in primary hyperparathyroidism-a case report

BACKGROUND

Intraoperative parathyroid hormone (IOPTH) monitoring is a critical surgical adjunct for determining the extent of surgery for primary hyperparathyroidism (PHPT), with reported false-positive and false-negative rates of up to 10%. Surgeons must understand the parathyroid hormone (PTH) dynamics and select the appropriate IOPTH protocol and interpretation criteria for curative surgery.

CASE PRESENTATION

We present the case of a 64-year-old woman with a large cystic parathyroid tumor and PHPT who experienced a significant delay in IOPTH decrease but was cured without additional surgery. The patient's basal intact PTH was 96.2 pg/mL, which decreased to 93.3 pg/mL at 25 min and 72.4 pg/mL at 55 min after removal of the parathyroid tumor. In an attempt to elucidate its pathophysiology, 1-84 PTH levels were measured in stored serum. These results can also be attributed to the relatively low basal PTH levels, intact PTH spike, and high ratio of large carboxyl-terminal PTH fragments present. The patient had normal intact PTH and calcium levels at the 9-month postoperative visit.

CONCLUSIONS

As detailed reports on these phenomena are scarce, we discuss the causes of false-negative IOPTH results in terms of PTH production, secretion, metabolism, and differences in measurement methods to avoid unnecessary surgery.

Investigating the effectiveness of intraoperative rapid parathyroid hormone assay in parathyroidectomy surgery in patients with secondary hyperparathyroidism

INTRODUCTION

The use of Rapid Intraoperative parathyroid hormone (Io-PTH) assay during surgery in the management of parathyroid tissue in cases of primary hyperparathyroidism has been proven to be effective, while its utilization in secondary hyperparathyroidism (SHPT) has been rarely reported. In the present study, we aim to demonstrate the application of rapid Io-PTH assay in patients with SHPT following chronic kidney disease undergoing parathyroidectomy surgery.

METHOD

In this prospective study, five blood samples were taken from patients undergoing parathyroidectomy and upper thymectomy. Among the samples, two were pre-excision, including prior to the first incision, after exploration, and before parathyroids resection. Two additional samples were taken 10 and 20 min after the excision of the parathyroid glands. Another sample was collected twenty-four hours after the operation. Serum Calcium levels and PTH levels were evaluated and analyzed.

RESULTS

We successfully managed SHPT in all 36 patients in our study. The patients included 24 males (66.7%) with a mean age of 49.97 ± 14.92. The mean PTH decreased significantly at 10 min, 20 min, one day, and six months after surgery (P < 0.001). The highest reduction occurred 10 min after removal of the parathyroid glands so the mean PTH compared to time zero was reduced from 1737 to 439, and in 100% of cases, more than 50% reduction was seen in PTH.

CONCLUSION

A 60% or more reduction in PTH Rapid at 10 min after parathyroidectomy has an accuracy of 94.4% and a positive predictive value of 100%. Thus, if the PTH level does not decrease by more than 60% at 10 min or more than 80% at 20 min, tissue exploration is continued with the aim of finding the ectopic parathyroid gland.

The American Association of Endocrine Surgeons Guidelines for the Definitive Surgical Management of Secondary and Tertiary Renal Hyperparathyroidism

OBJECTIVE

To develop evidence-based recommendations for safe, effective, and appropriate treatment of secondary (SHPT) and tertiary (THPT) renal hyperparathyroidism.

BACKGROUND

Hyperparathyroidism is common among patients with chronic kidney disease, end-stage kidney disease, and kidney transplant. The surgical management of SHPT and THPT is nuanced and requires a multidisciplinary approach. There are currently no clinical practice guidelines that address the surgical treatment of SHPT and THPT.

METHODS

Medical literature was reviewed from January 1, 1985 to present January 1, 2021 by a panel of 10 experts in SHPT and THPT. Recommendations using the best available evidence was constructed. The American College of Physicians grading system was used to determine levels of evidence. Recommendations were discussed to consensus. The American Association of Endocrine Surgeons membership reviewed and commented on preliminary drafts of the content.

RESULTS

These clinical guidelines present the epidemiology and pathophysiology of SHPT and THPT and provide recommendations for work-up and management of SHPT and THPT for all involved clinicians. It outlines the preoperative, intraoperative, and postoperative management of SHPT and THPT, as well as related definitions, operative techniques, morbidity, and outcomes. Specific topics include Pathogenesis and Epidemiology, Initial Evaluation, Imaging, Preoperative and Perioperative Care, Surgical Planning and Parathyroidectomy, Adjuncts and Approaches, Outcomes, and Reoperation.

CONCLUSIONS

Evidence-based guidelines were created to assist clinicians in the optimal management of secondary and tertiary renal hyperparathyroidism.

Interpretation of intraoperative parathyroid hormone monitoring according to the Rome criterion in primary hyperparathyroidism

Intraoperative parathyroid hormone dosage allows real-time monitoring of the decrease in PTH levels during parathyroidectomy and verify procedure's efficacy. Currently, none of the interpretative criteria used has absolute accuracy. The aim of this study is to evaluate diagnostic accuracy of the Rome criterion verifying diagnostic significance of the individual assays. A total of 205 patients with primary hyperparathyroidism from a single adenoma were retrospectively evaluated and monitored with baseline PTH, PTH at 10 min and PTH at 20 min after adenoma excision. The accuracy of the latter two assays compared with baseline was compared by ROC curves. In addition, was evaluated the influence on these data of localization diagnostics (ultrasounds and scintigraphy), definitive histology, and type of surgery performed. The ratio of 20-min sampling to baseline in the Rome criterion showed highest diagnostic significance. This finding was not influenced by the type of surgery performed, definitive histologic examination, or intraoperative localization of the adenoma. The Rome criterion has shown its high reliability in detecting persistence. The ratio of sampling at 20 min to baseline is by far the best performing. Further studies are needed to evaluate whether sampling at 10 min after adenoma excision can be considered not mandatory.

OUP accepted manuscript

Background

Several studies have reported on the use of intraoperative parathyroid hormone (ioPTH) measurements during parathyroidectomy (PTX) for renal hyperparathyroidism (rHPT), but there is no consensus on whether it is helpful and, if so, what protocol should be used. Therefore, the literature was systematically reviewed to assess a correlation between ioPTH and early postoperative parathyroid hormone (PTH) levels in patients undergoing PTX for rHPT, separately for those on dialysis and those with a functioning renal transplant.

Methods

A systematic literature search was performed in electronic databases. Quality assessment was performed using the Quality In Prognosis Studies tool. Mean ioPTH values were calculated at different time points and correlated to the postoperative PTH levels within 1 month. Fixed-effect and random-effects models were performed to assess the mean ioPTH levels at 10 or 20 min after resection (T10 and T20). Stratified analyses were performed for patients on dialysis and those with a functioning renal transplant.

Results

Of the 3087 records screened, 14 studies were included, including some 1177 patients; 1091 were on dialysis and 86 had a functioning kidney transplant. Risk of bias was moderate for most studies. For patients on dialysis, T10 and T20 mean ioPTH levels were 32.1 (95 per cent c.i. 24.3 to 39.9) pmol/l and 15.4 (95 per cent c.i. 7.8 to 22.9) pmol/l) in the random effects meta-analysis. Between individual studies, ioPTH ranged from 4.0–65.1 pmol/l at T10 and 8.6–25.7 pmol/l at T20. T10 and T20 ioPTH were 9.6 and 4.1 times the postoperative PTH—after T20 ioPTH stabilized in those on dialysis. In patients with a functioning renal transplant, ioPTH levels seemed to plateau after 10 min and measured 2.6 times the postoperative PTH.

Conclusion

There is a strong correlation between ioPTH and early postoperative PTH levels, indicating that ioPTH is potentially a useful instrument during PTX in patients with rHPT. For patients on dialysis, at T20 ioPTH levels have stabilized and are approximately four times the postoperative PTH. Therefore, it is recommended to use ioPTH 20 min after resection in patients on dialysis, which might be longer than necessary for those with a kidney transplant.

The effect of chronic kidney disease on intraoperative parathyroid hormone: A linear mixed model analysis

BACKGROUND

Reduced creatinine clearance is an indication for surgery in asymptomatic primary hyperparathyroidism, and a significant proportion of patients undergoing parathyroidectomy have chronic kidney disease. The purpose of this study was to evaluate the kinetics of intraoperative parathyroid hormone decline during parathyroidectomy in patients who have chronic kidney disease compared with those with who have normal renal function.

METHODS

This is a single-center, retrospective study of patients with primary hyperparathyroidism undergoing parathyroidectomy (n = 646). Patients were grouped based on estimated glomerular filtration rate greater than (normal renal function) or less than (chronic kidney disease) 60 mL/min/1.73m². All patients had intraoperative parathyroid hormone monitoring and ≥6-month postoperative serum studies to confirm surgical cure. Intraoperative parathyroid hormone kinetic curves were analyzed using a linear mixed model.

RESULTS

Despite similar pre-excision values, patients with chronic kidney disease had significantly higher intraoperative parathyroid hormone values at 5 minutes (76 vs 58 pg/mL, P = .02) and 10 minutes (54 vs 37 pg/mL, P = .004) postexcision. No significant difference was observed in whether patients met Miami criterion by 5 minutes (chronic kidney disease 71%, normal renal function 78%, P = .255) or by 10 minutes (chronic kidney disease 95%, normal renal function 96%, P = .751) postexcision. Using a linear mixed model, glomerular filtration rate did not have a significant effect on the change in intraoperative parathyroid hormone over time.

CONCLUSION

Patients with chronic kidney disease had significantly higher postexcision intraoperative parathyroid hormone levels. However, renal function did not affect the change in intraoperative parathyroid hormone over time, nor did renal function ultimately affect the likelihood of meeting the Miami criterion. Intraoperative parathyroid hormone monitoring remains useful in this population, although additional time points may be needed to observe normalization of values.

Intraoperative parathyroid hormone (IOPTH) assay might be better than the second-generation assay in parathyroidectomy for primary hyperparathyroidism

BACKGROUND

It is unclear whether the third-generation intraoperative parathyroid hormone assay can improve surgical outcomes over second-generation assay in primary hyperparathyroidism. We aimed to compare the rate of decrease and diagnostic accuracy between the two assays after parathyroid adenoma excision.

METHODS

Consecutive patients undergoing parathyroidectomy with intraoperative parathyroid hormone were analyzed. Blood was drawn before and 10 minutes and 20 minutes after excision of the adenoma. The same blood sample was run simultaneously in the second-generation assays (Elecsys PTH STAT) and third-generation assays (Elecsys 1-84 PTH). Biochemical cure meant >50% intraoperative parathyroid hormone decrease at 10 minutes. Cure meant normocalcemia 6 months after operation.

RESULTS

Relative to the second-generation assay, the value of the intraoperative parathyroid hormone level was less in the third-generation assay before excision (P < .001), at 10 minutes (P < .001), and at 20 minutes (P < .001). The intraoperative parathyroid hormone rate of decrease and the proportion of normalized post-excision intraoperative parathyroid hormone were greater in the third-generation assay (P < .001), but the prediction accuracy appeared similar between the 2 (91.5% vs 91.0%). Patients with worse renal function (estimated glomerular filtration rate <80mL/min/1.73m²) had a slower intraoperative parathyroid hormone decrease in the second-generation but not in the third-generation assay.

CONCLUSION

Despite comparable accuracy between the two generations of assay, the third-generation assay might be better than the second-generation assay because of the more rapid decrease in the intraoperative parathyroid hormone and a greater percentage of normalized intraoperative parathyroid hormone, regardless of baseline renal function.

Comparison between Second- and Third-Generation PTH Assays during Minimally Invasive Parathyroidectomy (MIP)

METHODS

112 patients (of which 72.3% females) underwent MIP by the same surgeon. Age, sex, body mass index (BMI), pre- and postoperative serum calcium, creatinine, 25(OH)D levels, PTH at baseline (PTH T0), and PTH at 10 minutes after adenoma resection (PTH T10) were recorded. Both PTH 2G and PTH 3G assays were assessed using the Diasorin assays.

RESULTS

The mean age was 56.1 ± 14.7 years. Mean value of BMI, preoperative calcium, 25(OH)D, and CKD-EPI-eGFR were, respectively, 26.8 ± 4.8 kg/m², 110.9 ± 7.9 mg/L, 19.3 ± 9.2 ng/mL, and 88.6 ± 25.6 mL/min/1.73 m². PTH 2G and PTH 3G assays were well correlated at PTH T0 and PTH T10 (respectively, correlation coefficient 0.74 and 0.72 for intraclass correlation type 3). The median PTH fall was, respectively, of 79.9% and 82.5% for PTH 2G and PTH 3G. Multivariate analysis using the combined PTH 2G and PTH 3G as a dependent variable with 2 repeated measurements (at PTH 0 and PTH 10) showed a significant effect of preoperative calcium on IOPTH fall (p=0.001, effect size 0.13), while no significant effects were observed for sex, age, BMI, and 25(OH)D.

CONCLUSION

PTH 2G and PTH 3G assays resulted in a similar drop in IOPTH values. Elevated preoperative calcium levels are the only independent predictor of IOPTH decline. Further studies are needed to determine other factors that can influence PTH kinetics.

Clinical Guidelines and PTH Measurement: Does Assay Generation Matter?

PTH is an important regulator of calcium and phosphate homeostasis and bone remodeling. It is metabolized into PTH fragments, which are measured to a different extent by PTH assays of different generations because of differences in fragments recognized and lack of assay standardization. PTH is measured in the workup of several conditions, and clinical guidelines provide recommendations concerning these measurements. This review provides an overview of the impact of differences between PTH assays, applying distinct clinical guidelines for primary and secondary hyperparathyroidism and perioperative use of PTH measurements. Guidelines deal with PTH measurement in different ways, recommending either trend monitoring, the use of a fold increase of the upper reference limit, or an absolute PTH cutoff value. For classic primary hyperparathyroidism (PHPT), the type of PTH assay used will not affect diagnosis or management because the precise concentration of PTH is less relevant. In chronic kidney disease, the guideline recommends treating secondary hyperparathyroidism above a twofold to ninefold PTH increase, which will result in different clinical decisions depending on the assay used. For patients after bariatric surgery, guidelines state absolute cutoff values for PTH, but the impact of different generation assays is unknown because direct comparison of PTH assays has never been performed. During parathyroid surgery, PTH measurements with a third-generation assay reflect treatment success more rapidly than second-generation assays. Increased awareness among clinicians regarding the complexity of PTH measurements is warranted because it can affect clinical decisions.

Parathyroid Hormone Fragments: New Targets for the Diagnosis and Treatment of Chronic Kidney Disease-Mineral and Bone Disorder

As a common disorder, chronic kidney disease (CKD) poses a great threat to human health. Chronic kidney disease-mineral and bone disorder (CKD-MBD) is a complication of CKD characterized by disturbances in the levels of calcium, phosphorus, parathyroid hormone (PTH), and vitamin D; abnormal bone formation affecting the mineralization and linear growth of bone; and vascular and soft tissue calcification. PTH reflects the function of the parathyroid gland and also takes part in the metabolism of minerals. The accurate measurement of PTH plays a vital role in the clinical diagnosis, treatment, and prognosis of patients with secondary hyperparathyroidism (SHPT). Previous studies have shown that there are different fragments of PTH in the body's circulation, causing antagonistic effects on bone and the kidney. Here we review the metabolism of PTH fragments; the progress being made in PTH measurement assays; the effects of PTH fragments on bone, kidney, and the cardiovascular system in CKD; and the predictive value of PTH measurement in assessing the effectiveness of parathyroidectomy (PTX). We hope that this review will help to clarify the value of accurate PTH measurements in CKD-MBD and promote the further development of multidisciplinary diagnosis and treatment.

Targeted surgical parathyroidectomy in end-stage renal disease patients and long-term metabolic control: A single-center experience in the current era

BACKGROUND

The long-term results of surgical parathyroidectomy (PTX) in end-stage renal disease (ESRD) patients are less well known in the modern era of newer activated vitamin-D analogs, calcimimetics and intraoperative monitoring of parathyroid hormone (PTH).

METHODS

We performed a retrospective chart review of all ESRD patients undergoing PTX at the University of Mississippi Medical Center between January 2005 and August 2011, with follow-up data as available up to 4 years. All PTXs were performed with intraoperative second-generation PTH monitoring and targeted gland size reduction.

RESULTS

The cohort (N = 37) was relatively young with a mean (±SD) age of 48.4 ± 13.9. 94.6% of the subjects were African American and 59.5% female. Preoperatively, 45.9% received cinacalcet (CNC) at a mean dose of 63.5 ± 20.9 mg. The size of the largest removed glands measured 1.7 ± 0.8 cm and almost all (94.6%) glands had hyperplasia on histology. The mean length of inpatient stay was 5.5 ± 2.4 days. Preoperative calcium/phosphorus measured 9.6 ± 1.2/6.6 ± 1.7 mg/dL with PTH concentrations of 1589 ± 827 pg/mL. Postoperative PTH values measured 145.4 ± 119.2 pg/mL. Preoperative PTH strongly correlated (P < 0.0001) with both alkaline phosphatase (ALP) levels (r: 0.596) and the number of inpatient days (r: 0.545), but not with CNC administration. Independent predictors for the duration of hospitalization were preoperative ALP (beta 0.469; P = 0.001) and age (beta -0.401; P = 0.005) (R² 0.45); for postoperative hypocalcemia, age (beta: -0.321; P = 0.006) and preoperative PTH (beta: 0.431; P = 0.036) were significant in linear regression models with stepwise selection.

CONCLUSION

Gland-sparing PTX achieved acceptable control of ESRD-associated hyperparathyroidism in most patients from a socioeconomically challenged, underserved population of the United States.

Niche point-of-care endocrine testing - Reviews of intraoperative parathyroid hormone and cortisol monitoring

Point-of-care (POC) testing, which provides quick test results in near-patient settings with easy-to-use devices, has grown continually in recent decades. Among near-patient and on-site tests, rapid intraoperative and intra-procedural assays are used to quickly deliver critical information and thereby improve patient outcomes. Rapid intraoperative parathyroid hormone (ioPTH) monitoring measures postoperative reduction of parathyroid hormone (PTH) to predict surgical outcome in patients with primary hyperparathyroidism, and therefore contributes to the change of parathyroidectomy to a minimally invasive procedure. In this review, recent progress in applying ioPTH monitoring to patients with secondary and tertiary hyperparathyroidism and other testing areas is discussed. In-suite cortisol monitoring facilitates the use of adrenal vein sampling (AVS) for the differential diagnosis of primary aldosteronism and adrenocorticotropic hormone (ACTH)-independent Cushing syndrome. In clinical and psychological research settings, POC testing is also useful for rapidly assessing cortisol in plasma and saliva samples as a biomarker of stress. Careful resource utilization and coordination among stakeholders help to determine the best approach for implementing cost-effective POC testing. Technical advances in integrating appropriate biosensors with microfluidics-based devices hold promise for future real-time POC cortisol monitoring.

The whole-PTH/intact-PTH ratio is a useful predictor of severity of secondary hyperparathyroidism

Background. The newer parathyroid hormone (PTH) assay, whole-PTH, uses an antibody that binds the region harbouring the first amino acid, making it specific for the complete molecule, 1–84-PTH. Especially among dialysis patients, it has been reported that the level of whole-PTH can be calculated as ∼60% of their intact-PTH value. In addition, since 1–84-PTH is part of intact-PTH, the whole-PTH/intact-PTH ratio should not theoretically exceed 1. However, an abnormally high 1–84-PTH/intact-PTH ratio is reported in a few patients with parathyroid carcinoma, primary hyperparathyroidism and secondary hyperparathyroidism. In this study, we examined the correlation between the 1–84-PTH/intact-PTH ratio and the severity of hyperparathyroidism in patients on haemodialysis (HD).

Patients and methods. The study population comprised 196 HD patients (males 113, females 83, age 67.4 ± 13.6 years, HD period 8.1 ± 7.3 years; mean ± SD). The whole-PTH/intact-PTH ratio was compared in patients with high PTH levels (intact-PTH ≥300 pg/ ml; high PTH group, n = 32), moderate PTH levels (intact-PTH >150–<300 pg/ml; moderate PTH group, n = 50) and low PTH levels (intact-PTH <150 pg/ml; low PTH group, n = 114). The ratio was also compared in 25 patients with at least one enlarged gland >0.5 cm³ suggesting nodular hyperplasia, as determined by power Doppler ultrasonography (hyperplasia group) with seven patients without enlarged gland (non-hyperplasia group) and six patients who had undergone total parathyroidectomy (post-PTx group).

Results. The whole-PTH/intact-PTH ratio of the high PTH group (0.68 ± 0.1) was significantly higher than those of the moderate (0.61 ± 0.1, P < 0.001) and low (0.52 ± 0.1, P < 0.001) groups. Moreover, the ratio was significantly higher in the hyperplasia group (0.70 ± 0.1) than those in the non-hyperplasia group (0.59 ± 0.1, P < 0.05) and post-PTx group (0.456 ± 0.12, P < 0.001).

Conclusions. The whole-PTH/intact-PTH ratio correlated with the severity of hyperparathyroidism. Our results suggest that the ratio might be a useful predictor of severity of secondary hyperparathyroidism in HD patients.

Intraoperative parathyroid hormone monitoring in neonatal severe primary hyperparathyroidism

Neonatal severe primary hyperparathyroidism presents in the first days of life with severe life-threatening hypercalcemia. It is associated with an inactivating homozygous mutation of the calcium sensing receptor gene. Total parathyroidectomy is the treatment of choice, so the surgeon must identify all the parathyroid tissue, including supernumerary and ectopic glands. We present the case of an infant who underwent total parathyroidectomy at age 4 months in which intraoperative parathyroid hormone monitoring provided immediate confirmation of surgical cure.

Usefulness of intraoperative parathyroid hormone measurements in patients with renal hyperparathyroidism

BACKGROUND

In renal hyperparathyroidism, it remains unclear whether intraoperative parathyroid hormone (PTH) measurements can predict postoperative outcome and guide the extent of surgical exploration.

METHODS

In 42 parathyroidectomies for renal hyperparathyroidism, we analyzed the predictive value of the Miami Criterion of 50% intraoperative PTH decrease. We used receiver operating characteristic (ROC) curves to find the criterion with the best diagnostic performance. We also investigated whether the whole PTH assay improved accuracy.

RESULTS

Twenty-six operations (62%) resulted in normal postoperative PTH. With the Miami Criterion, cure was predicted with a sensitivity of 95% and specificity of only 8%. Specificity could be improved to 50% using a 70% PTH decrease as cut-off level. The whole PTH assay did not improve accuracy.

CONCLUSION

Prediction of cure after parathyroidectomy for renal hyperparathyroidism might be improved with a criterion of 70% PTH decrease 10 minutes after excision of all parathyroid glands. Prospective analysis needs to validate this new criterion.

The opposing actions of the two parathyroid hormones, 1-84 PTH and 7-84 PTH: improvement in renal bone and calcium metabolism management

Bone biopsy, while invasive, is the gold standard for assessing bone status. According to published bone biopsy studies, half of the end-stage renal disease patients have adynamic bone disease. Compared to high-bone-turnover disease, adynamic bone disease has the higher mortality and is associated with arterial calcification. The treatment for high-bone-turnover disease is divergent from the treatment for adynamic bone disease. The parathyroid hormone (PTH) assay has been relied on as the routine, noninvasive diagnostic method to assess bone status. According to bone biopsy studies, the intact PTH assay has been demonstrated as ineffective at differentiating adynamic bone disease from normal and high-bone-turnover disease. For example, bone biopsy studies found the normal range for iPTH to be 451 to 1339 pg/mL and the range for adynamic bone disease to be 400 to 919 pg/mL. Intact PTH measures the sum of the two PTH hormones 1-84 PTH and 7-84 PTH. Specific 1-84 PTH assays neglect the role of the 7-84 PTH hormone, which is to lower bone turnover. According to independent bone biopsy studies, the 1-84 PTH/7-84 PTH ratio is 94% accurate in identifying adynamic bone disease and 94% accurate in assessing bone-turnover status.

Critical issues of PTH assays in CKD

Measurement of bioactive parathyroid hormone (PTH) is essential for the optimal management of secondary hyperparathyroidism and its associated bone disorders in chronic kidney disease (CKD) patients. For this purpose, three generations of increasingly specific PTH assays have been developed over the last 4 decades. To date, however, only second-generation PTH assays are most widely used, although these have been shown to cross-react with large PTH fragments having a partially preserved N-structure, mostly PTH(7-84). The newly developed third-generation PTH assays are believed to be the most specific means of measuring PTH(1-84), but their clinical utility remains debatable. More recently, these latter assays have also been shown to react with a new N-form of PTH, which has been identified in patients with severe hyperparathyroidism and parathyroid carcinoma. Progressive research in this area has advanced our understanding considerably regarding the circulating molecular forms of PTH and their pathophysiological roles in bone abnormalities associated with CKD. However, developing an ideal PTH assay continues to be difficult because of key issues such as the reliability of PTH as a surrogate marker for bone turnover, practicality of employing third-generation PTH assays, and unknown biological implications of N-PTH and other PTH fragments. Further research exploring these issues is mandatory to understand and optimally manage parathyroid disorders and bone abnormalities in CKD patients.

The pattern of the descent of PTH measured by intraoperative monitoring of intact-PTH in surgery for renal hyperparathyroidism

BACKGROUND

In the setting of total parathyroidectomy and autotransplantation surgery (TPTxAS) treatment for secondary hyperparathyroidism (SHPT) we evaluated whether intraoperative parathyroid hormone (iPTH) monitoring is an useful tool as a reference for total parathyroid removal.

DESIGN

Prospective open single value measurement efficacy study of one intraoperative (i.o.) diagnostic monitoring method (iPTH) on a cohort of surgical patients.

PATIENTS

All patients (n = 35) undergoing TP and SCTx at the Department of Surgery, Donostia Hospital from January 2002 to December 2006.

MAIN OUTCOME MEASURES

Serum levels of iPTH during surgery and prediction time of the of descent of PTH levels (measured in the clinic, at admission day and intra-operatively during induction of anesthesia, and every 5 and 10 minutes after removal of adenoma and 24 hours thereafter) were analyzed.

RESULTS

iPTH levels dropped clearly at ten minutes in all 35 patients and were non-measurable at 24 hours. iPTH decreased from pathological (1302.24 + 424.9 pg/ml) to half (50%) the values at the third intra-operative determination - minute 10 - (614.8 ± 196.62) and was undetectable at 24 hours.

CONCLUSIONS

Intra-operative measurement of iPTH is useful in the prediction of complete removal of all parathyroid tissue prior to autotransplantation thus avoiding persistence because of incomplete surgery.

[Evaluation of parathyroid function in presternal subcutaneous grafting after total parathyroidectomy for renal hyperparathyroidism]

INTRODUCTION

In the setting of total parathyroidectomy (TPT) and parathyroid transplantation (PTx) for renal hyperparathyroidism (RHP), we evaluated long-term parathyroid graft function after subcutaneous presternal transplantation (SCPTx).

HYPOTHESIS

Parathyroid glands are surrounded by fatty tissue. Therefore, we postulated that subcutaneous implantation of parathyroid tissue after TPT for RHP could be at least as effective as intramuscular grafting and would avoid the complications of the latter technique.

MATERIAL AND METHOD

We performed a study in a university hospital and its dialysis unit.

DESIGN

Prospective open efficacy study of a postoperative diagnostic monitoring method of intact parathyroid hormone (iPTH) in a cohort of surgical patients without loss to follow-up.

PATIENTS AND INTERVENTIONS

Thirty-five patients (19 women and 16 men) underwent TPT and SCPTx for RHP at the Department of General Surgery and Department of Nephrology, Donostia Hospital, San Sebastián, Gipuzkoa, Spain, from January 2002 to December 2005. Follow-up ranged from 6 to 42 months (mean, 15.4 months). Graft function was evaluated by measurement of plasma iPTH levels before surgery and 24 hours and 1, 3, 5, 15, 30, 60, 100 and 150 weeks after surgery. Reference values for PTH in our laboratory were 20-65 pg/mL.

RESULTS

The mean preoperative iPTH values were 1245 +/- 367.9 pg/mL (mean +/- SD) (range, 493-2160). After TPT and SCPTx, iPTH levels became undetectable in all patients at 24 hours. A value of 50 pg/mL was established as the criterion for adequate parathyroid graft function. The following values were obtained: 15.54 +/- 10.61 pg/mL (mean +/- SD) (range, 6-44) after 1 week, 57.2 +/- 1.9 pg/mL (mean +/- SD) (range, 43-74) after 5 weeks, 64.21 +/- 9.73 pg/mL (mean +/- SD) (range, 11.3-89) after 15 weeks, 75.12 +/- 9.05 pg/mL (mean +/- SD) (range, 24.6-104.2) after 30 weeks, 101.63 +/- 19.85 pg/mL (mean +/- SD) (range, 65-143) after 60 weeks, 121.63 +/- 27.85 pg/mL (mean +/- SD) (range, 62-179) after 100 weeks, 63 +/- 19.85 pg/mL (mean +/- SD) (range, 68-723) after 150 weeks and 102 +/- 18.65 pg/mL (mean +/- SD) (range, 68-113) after 200 weeks. The prevalence of hypoparathyroidism (serum iPTH level of < 20 pg/mL with a normal or low serum calcium concentration) was 2 out of 35 patients (5.71%) by week 60, with recovery of normal values by week 100. Graft-related recurrence occurred in one out of 35 patients (2.85%).

CONCLUSIONS

SCPTx after TPT and PTx for secondary RHP is an adequate method to replace muscular forearm parathyroid transplantation and avoid its complications. The functional results of TPT and SCPTx compare favorably with published data on other surgical techniques proposed for the treatment of RHP. Long-term follow-up of this series is currently being performed.

QuiCk-IntraOperative Bio-Intact PTH assay at parathyroidectomy for secondary hyperparathyroidism

BACKGROUND

In uremic patients, metabolism of 1-84 parathyroid hormone (PTH) and fragments are delayed, and in these patients, the usefulness of intraoperative PTH assay may be problematic. We evaluated the usefulness of the QuiCk-IntraOperative Bio-Intact PTH (QPTH) assay for uremic patients with secondary hyperparathyroidism who required total parathyroidectomy (PTx) with forearm autograft. The purpose of our study was to recognize whether QPTH in uremic patients was useful to determine during operation whether complete PTx had been achieved.

METHODS

Forty-four patients who underwent initial PTx were enrolled in this study. Blood samples were drawn just after induction of general anesthesia (basal samples), immediately after removal of the last gland, and at 5, 10, 15, and 30 minutes, and at the first morning after PTx. The assay was performed immediately after sample collection. Reductions of PTH levels were evaluated and expressed in percentage of basal levels.

RESULTS

The mean PTH levels in 41 patients, excluding 3 in whom the PTH level did not drop significantly (>60 pg/ml), measured by QPTH at anesthesia, 0, 5, 10, 15, and 30 minutes were 734.3, 104.7, 58.8, 37.4, 27.0, 16.3 pg/ml, corresponding to 100%, 17.1%, 9.3%, 5.8%, 4.1%, 2.4% of the preexcision values, respectively. If the cutoff value was defined as 10.8% at 10 minutes, the sensitivity was 100% and specificity 90%. When the QPTH level dropped to under 10.8% at 10 minutes, we could consider that all glands were removed.

CONCLUSIONS

QPTH in uremic patients is very useful to determine whether complete PTx is achieved during operation.

To autotransplant simultaneously or not -- can intraoperative parathyroid hormone monitoring reliably predict early postoperative parathyroid hormone levels after total parathyroidectomy for hyperplasia?

BACKGROUND

Intraoperative parathyroid hormone (IOPTH) monitoring is well-established in operation for primary hyperparathyroidism (HPT). In diseases where total parathyroidectomy (tPx) is a treatment option its reliability to predict postoperative residual parathyroid hormone (PTH) remains in question.

METHODS

Thirty-eight consecutive patients with tPx due to secondary autonomous renal (26 patients), familial (8 patients), or lithium-induced (4 patients) HPT were analyzed retrospectively for the relationship between IOPTH and postoperative PTH. Three concepts were tested to predict a postoperative PTH below the normal range: a mandatory intraoperative decline of PTH less than 50% and 90% of the baseline value as well as an intraoperative decline below a threshold of 100 pg/ml 10 minutes after tPx.

RESULTS

There was no significant correlation between IOPTH decline and postoperative PTH (R = .265; P = .108). In patients with a 4-gland resection (n = 34) the positive predictive value was 62.5% and the sensitivity was 90.9% for the '50% concept.' The corresponding values were 68.8% and 50.0% for the '90% concept,' and 81.8% and 81.8% for the '100 pg/ml concept.'

CONCLUSIONS

The decision for simultaneous autotransplantation after tPx can not be based on IOPTH monitoring, because the reliability in prediction of early postoperative PTH status is insufficient.

Parathyroid Subcutaneous Pre-sternal Transplantation after Parathyroidectomy for Renal Hyperparathyroidism. Long-term Graft Function

BACKGROUND

In the setting of total parathyroidectomy (TPT) and parathyroid transplantation (PTx) for renal hyperparathyroidism (RHP), we evaluated long-term parathyroid graft function after subcutaneous pre-sternal transplantation (SCPTx). Because parathyroid glands are surrounded by fatty tissue, we postulated that results of subcutaneous implantation of parathyroid tissue after total parathyroidectomy for renal hyperparathyroidism could be at least as successful as intramuscular grafting, but without its complications.

PATIENTS AND METHODS

The study, a prospective open efficacy study of postoperative (po) diagnostic monitoring of intact parathyroid hormone (iPTH) on a cohort of surgical patients, was conducted within a university hospital with a dialysis unit. Thirty five patients (19 women and 16 men) operated on for renal hyperparathyroidism underwent TPT and SCPTx for RHP at the Department of General Surgery and the Department of Nephrology. Donostia Hospital. San Sebastián. Gipuzkoa. Spain, from January 2002 to December 2005. Follow-up ranges from 6 months to 42 months (median: 15.4 months). The main outcome measure was evaluation of graft function by measurement of iPTH plasma level, based on serum levels of iPTH before operation and 24 h and 1, 3, 5, 15, 30, 60, 100, and 150 weeks after surgery.

RESULTS

Average preoperative iPTH values were 1,341.52 + 367.78 pg/ml (mean +/- SD) (range: 493-2,180). After TPT and PSCTx, iPTH levels became undetectable in all patients at 24 h. A level of 50 pg/ml was established as the criterion of adequate parathyroid graft function. Values obtained at the various time intervals were as follows: 14.14 + 7.73 1 pg/ml (mean +/- SD) (range: 6-36) after 1 week, 53 + 77.33 pg/ml (mean +/- SD) (range: 35-74) after 5 weeks, 62.95 + 20.93 pg/ml (mean +/- SD) (range: 11-89) after 15 weeks, 77.54 + 18.84 pg/ml (mean +/- SD) (range: 24.6-104.2) after 30 weeks, 109.29 + 50.22 pg/ml (mean +/- SD) (range: 54-327) after 60 weeks, 134.21 + 128.64 pg/ml (mean +/- SD) (range: 43-712) after 100 weeks, and 122.84 + 117.54 pg/ml (mean +/- SD) (range: 68-723) after 150 weeks. Prevalence of hypoparathyroidism (intact parathyroid hormone serum level < 20 pg/ml with a normal or low serum calcium concentration) was 2/35 (5.71%) by week 60 and recovered by week 100. Graft-related recurrence was 2.85% (1/35).

CONCLUSIONS

Subcutaneous pre-sternal transplantation (SCPTx) after TPT and PTx for secondary (RHP) is an adequate method to replace muscular forearm parathyroid transplantation and avoid its complications. Functioning results of total parathyroidectomy and presternal subcutaneous grafting compare favorably with the published data on other surgical techniques proposed for the treatment of renal hyperparathyroidism. Results of long-term follow-up exceed previously reported results.

The role of quick bio-intact PTH(1-84) assay during parathyroidectomy for secondary hyperparathyroidism

OBJECTIVE

The role of the quick PTH assay in surgery for secondary HPT is unclear because of overestimation of intact PTH(1-84) values due to the cross-reactivity of currently available first-generation PTH assays with non-PTH(1-84) fragments that accumulate in renal failure. In this study, we used a second-generation quick PTH immunometric assay that are claimed to detect the biologically active PTH(1-84) molecule with no cross-reactivity with PTH fragments to investigate the potential utility of the assay during parathyroidectomy for secondary HPT.

MATERIAL AND METHODS

The study was performed on 18 patients (12 women, 6 men) between October 2004 and March 2005. EDTA serum samples were drawn via a peripheral venous catheter after induction of anesthesia (basal), and at 5, 10, and 30 min after excision of diseased parathyroid glands. Serum active PTH(1-84) was measured by the quick Bio-Intact PTH(1-84) assay, which is a two-site chemiluminometric assay.

RESULTS

At 30 min the quick Bio-PTH(1-84) level of 16 patients was under 45 pg/mL. Four parathyroid glands were removed macroscopically from 12 of the 16 patients, and three glands were removed from the other four patients. All patients were cured of their HPT. Four enlarged parathyroid glands were removed from a patient whose Bio-Intact PTH(1-84) at 30 min had not fallen below 45 pg/mL, and no other glands were found by further exploration. At the 6 mo follow-up examination, the first-generation intact PTH level of this patient was over 45 pg/mL, but several diagnostic imaging methods did not reveal any enlarged parathyroid glands. Three enlarged parathyroid glands from the other patient, and exploration led to the identification of an ectopic parathyroid gland at the carotid bifurcation.

CONCLUSIONS

The results of this prospective study show that quick Bio-Intact PTH(1-84) monitoring is a valuable new tool for use in the surgical treatment of secondary HPT. An intraoperative, quick Bio-Intact PTH(1-84) assay will be of value for the adequate prediction of surgical cure.

Significance of monitoring Bio-Intact PTH (1-84) during parathyroidectomy for secondary hyperparathyroidism

BACKGROUND

The Bio-Intact PTH (1-84) assay has recently been developed to specifically measure the intact PTH (1-84) molecule, and in this study we used it to investigate sequential changes in serum Bio-Intact PTH (1-84) levels during parathyroidectomy for secondary HPT.

MATERIAL AND METHODS

The subjects of this study were 70 patients (41 women, 29 men) who underwent parathyroidectomy between April 2002 and March 2005. Ethylene diamine tetraacetic acid serum samples were drawn via a peripheral venous catheter after induction of anesthesia (basal), and at 5, 10, and 30 min after diseased glands excision. Serum active PTH (1-84) was measured by the Bio-Intact PTH (1-84) assay, which is a two-site chemiluminometric assay.

RESULTS

When 4 or more diseased parathyroid glands were removed, the basal of Bio-Intact PTH (1-84) level in patients without persistent HPT (52 cases) was 539 +/- 355 pg/mL. The level of the Bio-Intact PTH (1-84) at 30 min after sufficient parathyroidectomy had decreased to less than 45 pg/mL, whereas the Bio-Intact PTH (1-84) level in patients with persistent HPT at 30 min was greater than 45 pg/mL (3 cases). After removal of three or fewer diseased parathyroid glands (15 cases), the Bio-Intact PTH (1-84) at 30 min in patients without persistent HPT (13 cases) was less than 45 pg/mL. The 2 patients whose the Bio-Intact PTH (1-84) at 30 min was greater than 45 pg/mL underwent reoperation, and residual enlarged parathyroid gland in the neck was removed.

CONCLUSIONS

The Bio-Intact PTH (1-84) level at 30 min after parathyroidectomy seems to be useful for judging whether the parathyroidectomy is complete irrespective of the number of glands removed from patients with secondary HPT. When only three diseased parathyroid glands are removed, the surgeon can decide whether to continue or stop neck exploration according to the level of Bio-Intact PTH (1-84) at 30 min.

Accuracy of intra-operative PTH measurement during subtotal parathyroidectomy for tertiary hyperparathyroidism after renal transplantation

BACKGROUND AND AIMS

Intra-operative parathyroid hormone (IOPTH) results are not known in the setting of tertiary hyperparathyroidism (HPT) after renal transplantation.

MATERIALS AND METHODS

A retrospective analysis of 35 tertiary HPT patients who all underwent subtotal parathyroidectomy and IOPTH monitoring was conducted.

RESULTS

The mean follow-up time was 2.2+/-1.4 years. Thirty-four patients were cured; one patient (2.8%) had a persistent disease and was cured after reoperation. Median parathyroid hormone (PTH) (median percent decrease from highest) at baseline and at 5, 10, 20, and 30 min were 244, 78 (69%), 63 (75%), 53 (79%), and 49 pg/ml (83%), respectively. Four patients who were cured had a decrease of <50% at 5 min and two of them had a decrease of <50% at 10 min. The patient with persistent disease had a decrease of >50% at 10 min. The sensitivity of the test was 94% at 10 min using the Miami criteria.

CONCLUSION

This study shows that IOPTH in tertiary hyperparathyroidism has a high sensitivity. However, because of the low risk of persistent hyperparathyroidism when a subtotal parathyroidectomy is performed, its potential impact on the overall success rate is very small. We therefore do not recommend the routine use of IOPTH in tertiary hyperparathyroidism.

Parathyroid Hormone Monitoring during Total Parathyroidectomy for Renal Hyperparathyroidism: Pilot Study of the Impact of Renal Function and Assay Specificity

Background: Commonly used assays for intact parathyroid hormone (iPTH) detect not only the biologically active 84–amino acid hormone [PTH(1–84)], but cross-react with an N-terminal–truncated fragment. Because iPTH assays often fail to predict success of parathyroidectomy in patients with renal hyperparathyroidism (rHPT), we compared results of a 3rd-generation PTH(1–84) assay (Bio-iPTH; Nichols Institute Diagnostics) with two 2nd-generation iPTH assays (from Nichols and Roche Diagnostics) by evaluating the PTH clearance kinetics during surgical treatment.

Methods: We collected blood samples in short time intervals from 35 consecutive surgical patients with rHPT. Three patients had to be excluded from further calculations; the remainder were grouped according to kidney function and postoperative outcome. All samples were analyzed with the 3 automated PTH assays, which have different specificities.

Results: Twenty minutes after removal of the last gland, the PTH(1–84) values decreased to within the reference intervals in all patients with total and subtotal resection; however, iPTH concentrations normalized in only one half of these patients. In patients with poor renal function, the half-life of PTH(1–84) was shorter than the half-lives obtained with the iPTH assays.

Conclusions: The accuracy of PTH monitoring during surgery for rHPT depends on renal function and assay specificity. All assays tested showed similar effectiveness in detecting missed glands, but the assay for PTH(1–84) gave more reliable results than the iPTH assays, which overestimated the concentration of PTH and hampered the intrasurgical diagnosis of resection sufficiency.

Intraoperative parathyroid hormone measurement during minimally invasive parathyroidectomy: does it "value-add" to decision-making?

BACKGROUND

Routine use of intraoperative parathyroid hormone levels (IOPTH) during minimally invasive parathyroidectomy (MIP) has been challenged simply because the test works best when needed least, ie, once a solitary adenoma has been resected, and is less accurate with multiple gland disease. It has also been shown not to be cost-effective. The aim of this study was to determine if IOPTH "value-added" to decision-making during MIP.

STUDY DESIGN

The study group comprised 100 consecutive patients with sporadic hyperparathyroidism and an unequivocally positive sestamibi scan who were undergoing MIP in our unit from June 2004 until October 2005, from whom blood was collected for parathyroid hormone measurement preoperatively, preexcision, and at 10 and 30 minutes postremoval. No action was taken on the results of the test.

RESULTS

Ninety-eight patients were cured by MIP alone. Two patients had persistent hyperparathyroidism, one of whom was cured with subsequent open reexploration and removal of a second adenoma, and the other remains hypercalcemic despite additional open neck exploration. IOPTH in both patients failed to fall in retrospect, only the first would have been cured by conversion at the time of operation. The value-added accuracy of IOPTH was really only 1%. In an additional nine patients, IOPTH at 10 minutes had failed to fall by > 50% from the highest level, those patients (9%) would have been subjected to an unnecessary conversion on the basis of a false-negative result.

CONCLUSIONS

IOPTH does not substantially value-add to decision-making during MIP. Most patients will be cured with appropriate selection for MIP based on preoperative localization studies.

Overproduction and Secretion of a Novel Amino-Terminal Form of Parathyroid Hormone from a Severe Type of Parathyroid Hyperplasia in Uremia

Measurement of bioactive parathyroid hormone (PTH) is essential for optimal management of bone abnormalities in dialysis patients. This can be accomplished by PTH measurements using third-generation PTH assays, which detect more or less of the first six amino acids of the PTH structure. Such assays do not detect non-(1-84) PTH fragments, such as human PTH (7-84), which are recognized by the second-generation PTH assays that use a detection antibody that recognizes an epitope within the 13-34 region of the PTH structure. Therefore, third-generation PTH results are expected to be lower than those that are obtained with second-generation PTH assays. Rare exceptions to this rule have been reported for patients with severe primary hyperparathyroidism or parathyroid cancer. Sera and gland extracts were analyzed from a dialysis patient with high bone turnover disease and with surprising higher PTH levels by a third-generation assay than by a second-generation assay. This finding normalized after the surgical removal of an enlarged gland with a single nodule, an advanced type of nodular hyperplasia. HPLC fractionation of sera and gland extracts revealed the overproduction and secretion of a PTH molecule with an intact amino-terminus structure distinct from (1-84) PTH. This form of PTH was readily detectable by third-generation PTH assays but was poorly reactive in second-generation PTH assays. Therefore, parathyroid glands with advanced uremic nodular hyperplasia may overproduce and secrete a novel, biologically active form of PTH with an intact 1-6 region but a presumably modified 12-18 region required for the detection in second-generation PTH assays.

Intraoperative monitoring of intact PTH in surgery for renal hyperparathyroidism as an indicator of complete parathyroid removal

In the setting of total parathyroidectomy and autotransplantation surgery (TPT x AS) as treatment for secondary hyperparathyroidism (SHPT), we evaluated whether intraoperative parathyroid hormone (iPTH) monitoring is useful as a reference for total parathyroid removal. We conducted a prospective, open, single value measurement efficacy study of the intraoperative (i.o.) diagnostic monitoring of iPTH in a cohort of surgical patients. All patients (n = 25) underwent TPT x AS at the Department of Surgery, Donostia Hospital from January 2002 to October 2004. The primary outcome measures were kinetics of serum levels of iPTH during surgery and prediction time of the of descent of PTH levels (measured in the clinic on the day of admission and intraoperatively during induction of anesthesia, every 5 and 10 minutes after removal of the adenoma, and again 24 hours thereafter). iPTH levels returned to normal in all 25 patients, decreasing from pathological levels at the beginning of the operation (1302.24 + 424.9 pg/ml) to half (50%) values at the third intraoperative determination, minute 10 (614.8 +/- 196.62), becoming undetectable at 24 hours. Frozen sections were conclusive for parathyroid tissue (20.56 + 10.3 minutes after removal). Intraoperative measurement of iPTH is useful in the prediction complete removal of all parathyroid tissue prior to autotransplantation, thus avoiding persistence of disease because of incomplete surgery.

Impact of intraoperative parathyroid hormone levels on surgical results in patients with renal hyperparathyroidism

The aim of our study was to evaluate the impact of intraoperative parathyroid hormone (PTH) measurement on surgical results in patients with renal hyperparathyroidism (HPT). From December 1999 to February 2004, a series of 95 consecutive patients underwent total parathyroidectomy and intraoperative PTH measurement for renal HPT. Intraoperative PTH was measured before and 15 minutes after parathyroidectomy with the Immulite DPC assay for intact PTH. The median PTH levels before surgery were 133.0 pmol/L, which declined to 5.9 pmol/L at the end of the operation. At follow-up, 91 of 95 (96%) patients presented with normal calcium levels. Persistent renal HPT was seen in three patients, and recurrent HPT was diagnosed in another. In 99% of the patients the intraoperative PTH levels declined more than 50% and in 73% the PTH decay was more than 90%. In 64% of the patients PTH levels dropped into the normal range (< 7.6 pmol/L). Altogether, 97% of the patients with an intraoperative PTH decrease of more than 90% presented with normal PTH levels postoperatively (p = 0.0237), as did all of the patients whose intraoperative PTH dropped into the normal range (p = 0.0432). Intraoperative PTH measurement with a decrease in intraoperative PTH of at least 90% is highly predictive of successful parathyroidectomy and normalization of postoperative calcium and PTH levels.

Usefulness of whole PTH assay in patients with renal osteodystrophy —Correlation with bone scintigraphy

OBJECTIVE

Intact parathyroid hormone (PTH) assay has recently been reported to be effective in evaluating both 1-84 PTH (whole PTH) and inactive 7-84 PTH. Inactive 7-84 PTH is considered to be increased in hemodialysis patients and to prevent the effects of 1-84 PTH, and intact PTH is considered to overestimate the PTH activity in these patients. As such, a whole PTH assay has recently been developed. The purpose of this study was to examine the usefulness of a whole PTH assay using the bone to soft tissue (B/ST) ratio on bone scintigraphy.

METHOD

Twenty-five hemodialysis patients were included in our study. In all patients, bone scintigraphy and a blood test [whole PTH, intact PTH, alkaline phosphatase (ALP), calcium (Ca), and phosphorus (P)] were performed. Regions of interest (ROIs) were drawn around the cranium, lumbar vertebrae, left femoral neck, and soft tissue of the medial left thigh to obtain the B/ST ratio.

RESULTS

The B/ST ratio of the cranium and left femoral neck correlated with whole PTH and intact PTH. In particular, the B/ST ratio of the cranium correlated most significantly with the value of whole PTH. Whole PTH levels correlated with intact PTH levels (r = 0.891, p < 0.0001).

CONCLUSION

Our data indicate that a whole PTH assay may be useful in evaluating PTH activity using the B/ST ratio. The B/ST ratio of the cranium may reflect the bone metabolism of hemodialysis patients.

Quick PTH assay cannot predict incomplete parathyroidectomy in patients with renal hyperparathyroidism

BACKGROUND

Contradictory reports on the value of intraoperative quick parathyroid hormone (PTH) monitoring in renal hyperparathyroidism have been published.

METHODS

Thirty-five consecutive patients underwent total parathyroidectomy, central neck dissection, bilateral thymectomy, and immediate autotransplantation. PTH levels were measured by PTH assay at induction of anesthesia (baseline level) and in 5-minute intervals after excision of the last parathyroid gland. Parathyroidectomy was considered "total" in patients with PTH levels <10 pg/mL (subgroup 1), "subtotal" between 10 and 65 pg/mL (subgroup 2) and "insufficient" at >65 pg/mL (subgroup 3) within the first postoperative week.

RESULTS

Fifteen minutes after excision of the last gland, PTH levels dropped to 19.4 +/- 15.7% (subgroup 1), 14.9 +/- 5.9% (subgroup 2), and 18 +/- 6.7% (subgroup 3) from baseline among 22 patients on hemodialysis, to 22.1 +/- 18.7% and 17.5% in 9 patients (subgroups 1 and 2) after successful kidney transplantation, and to 10.7% and 17.5% (subgroup 1) and 12.8% and 31.4% (subgroup 2) in 4 patients with reduced renal function after kidney transplantation.

CONCLUSIONS

Currently available QPTH assays are not useful to predict insufficient resection of hyperfunctioning parathyroid tissue.

[Parathyroid hormone values obtained with immunometric assays depend on the amino-terminal antibody specificity]

Introduction of 2nd generation immunometric assays for the measurement of serum parathyroid hormone (PTH), turned them more available, simple and rapid. These methods, based on double identification of the PTH molecule, supposedly measure the intact, bioactive molecule, with the sequence 1-84. Recent works showed that they also measure forms with amino-terminal deletions, like the 7-84 form, which are not able to activate the traditional PTH receptor (PTH1R). Thus, an important practical aspect is the definition of the PTH forms measured by the immunometric assays, a fact that depends on the specificity of the antibodies employed. In this report we compare the results obtained with an in-house immunofluorometric assay that presents a cross-reactivity of 50% with the 7-84 PTH sequence, and two commercial 2nd generation assays, that react 100%. In a first study, 135 samples were measured using our assay and an electrochemiluminescent assay, resulting in a correlation coefficient of 0.961 (P<0.0001) and medians of 35.0 and 51.0 ng/L (P<0.0001). In a second study, 252 samples were analyzed using our assay and an immunochemiluminometric assay, resulting in a correlation of 0.883 (P<0.0001) and medians of 36.0 and 45.5 ng/L (P<0.0001). In both studies results obtained with the in-house assay were significantly lower, as expected by the specificity of the anti-amino-terminal antibody employed. Our data support the need of a precise description of the specificity of the amino-terminal antibodies employed in 2nd generation PTH assays in order to better compare results and define normal ranges.

Predictive value of intact parathyroid hormone measurement during surgery for renal hyperparathyroidism

BACKGROUND AND AIMS

In contrast to that in patients with primary hyperparathyroidism, the value of intraoperative intact parathyroid hormone (iPTH) measurement is still unclear in patients with renal hyperparathyroidism and was, therefore, evaluated in a large cohort of patients.

PATIENTS

Intraoperative iPTH measurement was performed in 153 patients with renal hyperparathyroidism (129 with terminal renal failure and 24 with functioning kidney graft). Subtotal and total parathyroidectomy were performed in 123 and 13 patients, respectively, during initial surgery. In patients with recurrent disease (17), the respective hyperfunctioning tissue was removed. Intraoperative blood samples were obtained by puncture of the internal jugular vein before preparation of the parathyroids (PTH0) and 15 min after parathyroidectomy (PTH15). iPTH was measured with the Elecsys 2010 system. Postoperative iPTH levels (PTH(post)) were determined at postoperative days 1 to 3 and at week 2. Patients were arbitrarily divided in four groups according to the postoperative iPTH values: 0-25 pg/ml (group 1), 26-65 pg/ml (group 2), 66-150 pg/ml (group 3) and more than 150 pg/ml (group 4).

RESULTS

The mean PTH0 value was 869+/-57 pg/ml, which decreased to 167+/-15 pg/ml at PTH15. The mean relative PTH15 value was 21.6+/-1.7%. Postoperatively, iPTH decreased to 42+/-9 pg/ml. The postoperative iPTH value of the 129 patients with terminal renal failure was 25 pg/ml or less in 99 patients, 26-65 pg/ml in 11 patients, 66-150 pg/ml in eight patients and higher than 150 pg/ml in 11 patients. Two successive criteria of iPTH decrease were used: first, a PTH15 of < or =150 pg/ml or, second, a relative PTH15 of < or =30% less was used. Fifteen patients did not fulfil both criteria. In 13 of them (86.7%) iPTH(post) was higher than 65 pg (true failure to decline). Of 114 patients who fulfilled the criteria, 108 (94.7%) had normal postoperative iPTH values (true decline). Absolute PTH15 values of less than 150 pg/ml predicted normal postoperative iPTH levels in 77 of 78 patients.

CONCLUSION

A PTH15 value of 150 pg/ml or less predicts operative success in patients with renal failure in 98.7% of cases, independently of the relative decay. In contrast, if the relative PTH15 is higher than 30%, high postoperative PTH values are predicted with a probability of 86.7%. Although there remain some borderline cases, intraoperative iPTH measurement is accurate and also can be useful in patients with renal hyperparathyroidism.